Assembly Press Any Key to Continue
Keyboard input/Obtain a Y or N response
You are encouraged to solve this task according to the task description, using any language you may know.
- Task
Obtain a valid Y or N response from the keyboard.
The keyboard should be flushed, so that any outstanding key-presses are removed, preventing any existing Y or N key-press from being evaluated.
The response should be obtained as soon as Y or N are pressed, and there should be no need to press an enter key.
8080 Assembly [edit]
This program uses CP/M to read the keyboard.
rawio: equ 6 ; Raw console input puts: equ 9 ; String output bdos: equ 5 ; CP/M entry point org 100h jmp demo ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;; Routine: read 'Y' or 'N' from the keyboard. ;;; Output: carry flag clear if Y pressed, set if N pressed. yesno: mvi c,rawio ; Read input from console mvi e,-1 call bdos ana a ; Read keys as long as a key is pressed jnz yesno ; (wait until keyboard is clear) yread: mvi c,rawio ; Then, wait for a key to be pressed mvi e,-1 call bdos ana a jz yread ori 32 ; Set bit 5 to make input letters lowercase cpi 'y' ; If the key is Y, rz ; then return (carry is clear here) cpi 'n' ; If the key is N, stc ; then set the carry flag and return rz jmp yread ; If it wasn't Y or N, get another key ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;; Demo code: use the routine to read Y or N, and then print ;;; 'yes' or 'no'. demo: call yesno ; Read Y or N mvi c,puts lxi d,yes jnc bdos ; If carry clear, print 'Yes' lxi d,no jmp bdos ; Otherwise, print 'No' yes: db 'Yes$' no: db 'No$' 8086 Assembly [edit]
- Assembled using UASM v2.49
.model small .stack 1024 .data ;no data needed .code start: mov ax , @ code mov ds , ax call PRIMM BYTE " Exit program and return to MS-DOS ? ( Y / N ) " , 0 mov ax , 0 C00h int 21 h ;flush keyboard buffer forever: call waitKey ;returns ASCII code in AL and AL , 11011111 b ;ignore case cmp al , " Y " jz ReturnToMSDOS cmp al , " N " jz forever ;normally this would jump somewhere else but for simplicity it will wait ;for a yes response. jnz forever ReturnToMSDOS : mov ax , 0 C00h int 21 h ;flush keyboard buffer mov ax , 4 C00h int 21 h ;end program ;------------------------------------------------------------------- ; SUBROUTINES ;------------------------------------------------------------------- waitKey: mov ah , 01 h int 16 h jz waitKey ret ;waits until a key is pressed. ;return: ; AL = ASCII CODE ; AH = SCAN CODE (???) ;------------------------------------------------------------------- PrintString: ;Print null-terminated strings ;input: string address = ds:si lodsb ;Load a letter cmp al , 0 ;Was that letter the terminator? jz PrintString_Done ;Yes? then RET call PrintChar ;Print to screen jmp PrintString ;Repeat PrintString_Done: ret ;------------------------------------------------------------------- PrintChar: push ax mov ah , 0 Eh int 10 h ;print AL to the screen. pop ax ret ;------------------------------------------------------------------- PrintSpace: mov al , ' ' jmp PrintChar ;JMP avoids a tail call. ;ret ;"PrintChar"'s ret will do this for us. ;------------------------------------------------------------------- NewLine: push dx push ax mov ah , 02 h mov dl , 13 ;CR int 21 h mov dl , 10 ;LF int 21 h pop ax pop dx ret ;------------------------------------------------------------------- PRIMM: pop si push ax ;get return address in si, this is the source offset for ;the string that will be printed. ;String must be null terminated. call PrintString pop ax push si ;PrintString adjusts the return address for us, it is now ;just after the null terminator. So put it back on the stack. ret ;------------------------------------------------------------------- end start 8th [edit]
\ get a yes or no response from the keyboard : yes-no con:key $20 bor dup 'y n:= if ;; then dup 'n n:= if ;; then drop yes-no ; : no? 'n n:= if "No" else "Yes" then . ; "Yes or no? " con:print yes-no no? cr bye Action! [edit]
PROC MAIN() Byte Key=764 Printe("Press Y or N to continue") key=255 Do Until Key=43 or Key=35 Od Print("You pressed ") If Key=43 then Printe("Yes") Fi If Key=35 then Printe("No ") Fi RETURN Ada [edit]
function Yes_Or_No ( Prompt : String := "Your answer (Y/N): " ) return Boolean is Answer : Character ; begin Ada . Text_IO . Put ( Prompt ); loop Ada . Text_IO . Get_Immediate ( Answer ); case Answer is when ' Y '|' y ' => return True ; when ' N '|' n ' => return False ; when others => null ; end case ; end loop ; end Yes_Or_No ; AutoHotkey [edit]
Loop , { Input , Key , L1 if ( Key = "n" || Key = "y" ) break } MsgBox , % "The response was "" " Key " "" ." ExitApp AWK [edit]
# syntax: GAWK -f KEYBOARD_INPUT_OBTAIN_A_Y_OR_N_RESPONSE.AWK BEGIN { printf ( "you entered %s\n" , prompt_user ()) exit ( 0 ) } function prompt_user ( rec ) { # AWK lacks the ability to get keyboard input without pressing the enter key. while ( 1 ) { printf ( "enter Y or N " ) getline rec < "con" gsub ( / / , "" , rec ) # optional if ( rec ~ /^[nyNY]$/ ) { break } } return ( rec ) } enter Y or N y you entered y
Axe [edit]
Since the TI-83/84 require a modifier key to access the letters, this example uses the 2nd key as Y and the Clear key as N.
While getKey(0) End While 1 If getKey(15) Disp "N",i Return ElseIf getKey(54) Disp "Y",i Return End End BASIC [edit]
Applesoft BASIC [edit]
10 LET C = PEEK (49168): REM CLEAR KEYBOARD 20 PRINT "PRESS Y OR N TO CONTINUE" 30 GET K$ 40 IF K$ < > "Y" AND K$ < > "N" THEN 30 50 PRINT "THE RESPONSE WAS ";K$ BASIC256 [edit]
print "Do you want to continue y/n : " ; do KBD$ = key until KBD$ = "89" or KBD$ = "78" print chr ( KBD$ ) if KBD$ = "89" then print "OK, continuing" else print "OK, finishing" end if QBasic [edit]
PRINT "Press Y or N to continue." DO KBD$ = "" WHILE KBD$ = "" KBD$ = UCASE$ ( INKEY$ ) WEND IF KBD$ <> "Y" AND KBD$ <> "N" THEN BEEP LOOP UNTIL KBD$ = "Y" OR KBD$ = "N" PRINT "The response was " ; KBD$ BBC BASIC [edit]
REPEAT UNTIL INKEY$ ( 0 ) = "" PRINT "Press Y or N to continue" REPEAT key$ = GET$ UNTIL key$ = "Y" OR key$ = "N" PRINT "The response was " key$ Commodore BASIC [edit]
10 PRINT "PRESS Y OR N TO CONTINUE:" ; 20 POKE 198 , 0 : REM CLEAR KEY BUFFER 30 GET K$ 40 IF K$ <> "Y" AND K$ <> "N" THEN 30 50 PRINT K$ Note that 198 is the location of the keyboard buffer index on the VIC-20, C-64, and C-128. On the PET, the correct location is 158, while on the Plus/4 and C-16, it's 239.
The loop on lines 30 - 40 will cycle as fast as the interpreter can go, assigning K$ the empty string until the user presses a key. On versions of BASIC later than the 2.0 on the VIC and 64 (e.g. 3.5 on the C-16 and Plus/4, 7.0 on the C-128), GETKEY may be used in place of GET. GETKEY will wait for the user to press a key before continuing, so the polling is done in the BASIC interpreter's machine language code, and the BASIC loop only cycles when the user presses a key other than Y or N.
GW-BASIC [edit]
10 CLS : PRINT "Press Y or N to continue." 20 WHILE T$ <> "y" AND T$ <> "Y" AND T$ <> "n" AND T$ <> "N" 30 T$ = "" 40 WHILE T$ = "" 50 T$ = INKEY$ 60 WEND 70 IF T$ <> "y" AND T$ <> "Y" AND T$ <> "n" AND T$ <> "N" THEN BEEP 80 WEND 90 PRINT "The response was " ; T$ GW-BASIC variant [edit]
10 DEF FNUP$ ( C$ ) = CHR$ ( ASC ( C$ ) -32 * ( ASC ( C$ ) > 96 ) * ( ASC ( C$ ) < 123 )) 20 CLS : PRINT "Press Y or N to continue." 30 WHILE T$ <> "Y" AND T$ <> "N" 40 T$ = FNUP$ ( INPUT$ ( 1 )) 50 IF T$ <> "Y" AND T$ <> "N" THEN BEEP 60 WEND 70 PRINT "The response was: " ; T$ IS-BASIC [edit]
100 GET K$ ! Flush the keyboard buffer 110 PRINT "Press Y or N to continue." 120 DO 130 LET K$=LCASE$(INKEY$) 140 LOOP UNTIL K$="y" OR K$="n" 150 PRINT "The response was ";K$ Locomotive Basic [edit]
10 CLEAR INPUT 20 PRINT "Press Y or N to continue" 30 a$ = LOWER$ ( INKEY$ ) 40 IF a$ = "" THEN 30 50 IF a$ = "y" THEN PRINT "Yes" : END 60 IF a$ = "n" THEN PRINT "No" : END 70 PRINT "Try again" 80 GOTO 30 Yabasic [edit]
clear screen print "Do you want to continue y/n : "; repeat KBD$ = lower$(inkey$) until KBD$ = "y" or KBD$ = "n" print KBD$ if KBD$ = "y" then print "OK, continuing" else print "OK, finishing" end if ZX Spectrum Basic [edit]
Note that this will also work in GW-BASIC and most QBasic-compatible BASICs if all instances of "GO TO" are changed to "GOTO".
10 IF INKEY$ <> "" THEN GO TO 10 : REM flush the keyboard buffer 20 PRINT "Press Y or N to continue" 30 LET k$ = INKEY$ 40 IF k$ <> "y" AND k$ <> "Y" AND k$ <> "n" AND k$ <> "N" THEN GO TO 30 50 PRINT "The response was " ; k$ Batch File [edit]
@ echo off choice if errorlevel 2 echo You chose N if errorlevel 1 echo You chose Y >nul pause C [edit]
For POSIX compliant systems (in theory that includes WinNT family).
#include <stdio.h> #include <termios.h> #include <unistd.h> #include <fcntl.h> #include <sys/time.h> void set_mode ( int want_key ) { static struct termios old , new ; if ( ! want_key ) { tcsetattr ( STDIN_FILENO , TCSANOW , & old ); return ; } tcgetattr ( STDIN_FILENO , & old ); new = old ; new . c_lflag &= ~ ( ICANON ); tcsetattr ( STDIN_FILENO , TCSANOW , & new ); } int get_key ( int no_timeout ) { int c = 0 ; struct timeval tv ; fd_set fs ; tv . tv_usec = tv . tv_sec = 0 ; FD_ZERO ( & fs ); FD_SET ( STDIN_FILENO , & fs ); select ( STDIN_FILENO + 1 , & fs , 0 , 0 , no_timeout ? 0 : & tv ); if ( FD_ISSET ( STDIN_FILENO , & fs )) { c = getchar (); set_mode ( 0 ); } return c ; } int main () { int c ; while ( 1 ) { set_mode ( 1 ); while ( get_key ( 0 )); /* clear buffer */ printf ( "Prompt again [Y/N]? " ); fflush ( stdout ); c = get_key ( 1 ); if ( c == 'Y' || c == 'y' ) { printf ( " \n " ); continue ; } if ( c == 'N' || c == 'n' ) { printf ( " \n Done \n " ); break ; } printf ( " \n Yes or no? \n " ); } return 0 ; } C# [edit]
using System; namespace Y_or_N { class Program { static void Main() { bool response = GetYorN(); } static bool GetYorN() { ConsoleKey response; // Creates a variable to hold the user's response. do { while (Console.KeyAvailable) // Flushes the input queue. Console.ReadKey(); Console.Write("Y or N? "); // Asks the user to answer with 'Y' or 'N'. response = Console.ReadKey().Key; // Gets the user's response. Console.WriteLine(); // Breaks the line. } while (response != ConsoleKey.Y && response != ConsoleKey.N); // If the user did not respond with a 'Y' or an 'N', repeat the loop. /* * Return true if the user responded with 'Y', otherwise false. * * We know the response was either 'Y' or 'N', so we can assume * the response is 'N' if it is not 'Y'. */ return response == ConsoleKey.Y; } } } C++ [edit]
Windows specific
#include <conio.h> #include <iostream> using namespace std ; int main () { char ch ; _cputs ( "Yes or no?" ); do { ch = _getch (); ch = toupper ( ch ); } while ( ch != 'Y' && ch != 'N' ); if ( ch == 'N' ) { cout << "You said no" << endl ; } else { cout << "You said yes" << endl ; } return 0 ; } Clojure [edit]
Note: If you run it with Leiningen, use the special trampoline run to prevent issues:
$ lein trampoline run
( ns yprompt.core ( :import jline.Terminal ) ( :gen-class )) ( defn yes? [ k ] ( if ( or ( = k 89 ) ( = k 121 )) true false )) ( defn prompt [] ( println "\nPrompt again [Y/N]?" ) ( let [ term ( Terminal/getTerminal ) ykey ( yes? ( .readCharacter term System/in ))] ( if-not ykey ( recur ) ( println "Yes!" )))) ( defn -main [ & args ] ( prompt )) Common Lisp [edit]
LispWorks [edit]
Version 1:
( defun rosetta-y-or-n () ( clear-input *query-io* ) ( y-or-n-p )) Version 2:
( defun y-or-n () ( clear-input *standard-input* ) ( loop as dum = ( format t "Y or N for yes or no: " ) as c = ( read-char ) as q = ( and ( not ( equal c #\n )) ( not ( equal c #\y ))) when q do ( format t "~%Need Y or N~%" ) unless q return ( if ( equal c #\y ) 'yes 'no ))) Version 1 and 2 work as required in a LispWorks GUI interface, i.e. they return immediately when the y or n keys are pressed, without waiting for the Enter key.
ncurses [edit]
When called from a REPL in a Linux terminal, y-or-n-p is line buffered, which means any input has to be confirmed by an Enter key.
In order to have keys available immediately to the program, line buffering has to be disabled in the tty driver. This can be done by utilizing the ncurses terminal library available on most GNU/Linux systems. To interface ncurses from Lisp, the croatoan library can be used:
Version 3:
( defun y-or-no () ( with-screen ( scr :input-buffering nil :input-blocking t ) ( clear scr ) ( princ "Do you want to continue? [Y/N]" scr ) ( refresh scr ) ( event-case ( scr event ) (( #\Y #\y ) ( return-from event-case t )) (( #\N #\n ) ( return-from event-case nil ))))) D [edit]
import std . stdio : stdout , write , writefln ; extern ( C ) nothrow { void _STI_conio (); void _STD_conio (); int kbhit (); int getch (); } void main () { _STI_conio (); write ( "Enter Y or N: " ); stdout . flush (); int c ; do { while (! kbhit ()) {} c = getch (); // Visual feedback for each keypress. write ( cast ( char ) c ); stdout . flush (); } while ( c != 'Y' && c != 'y' && c != 'N' && c != 'n' ); writefln ( "\nResponse: %c" , cast ( char ) c ); _STD_conio (); } Enter Y or N: abcN Response: N
Delphi [edit]
Thanks for JensBorrisholt [1].
program Obtain_a_Y_or_N_response ; {$APPTYPE CONSOLE} uses System . Console ; function GetKey ( acepted : string ) : Char ; var key : Char ; begin while True do begin if Console . KeyAvailable then begin key := UpCase ( Console . ReadKey () . KeyChar ) ; if pos ( key , acepted ) > 0 then exit ( key ) ; end ; end ; Result := #0 ; // Never Enter condition end ; begin Console . WriteLine ( 'Press Y or N' ) ; case GetKey ( 'YN' ) of 'Y' : Console . WriteLine ( 'You pressed Yes' ) ; 'N' : Console . WriteLine ( 'You pressed No' ) ; else Console . WriteLine ( 'We have a error' ) ; end ; Readln ; end . Press Y ou N You pressed Yes
EGL [edit]
handler YesOrNoHandler type RUIhandler{initialUI =[ui], onConstructionFunction = start} ui Div { }; const KEY_N int = 78; const KEY_Y int = 89; function start() document.onKeyDown = d_onKeyDown; end function d_onKeyDown(e Event in) case (e.ch) when (KEY_N) ui.innerText = "N pressed."; when (KEY_Y) ui.innerText = "Y pressed."; end e.preventDefault(); end end Elm [edit]
import Char import Graphics.Element exposing ( Element , empty , show ) import Keyboard view : Int -> Element view keyCode = let char = Char . fromCode keyCode showChar = toString >> ( (++) "The last (y/n) key pressed was: " ) >> show in case char of ' n' -> showChar char ' y' -> showChar char _ -> empty main : Signal Element main = Signal . map view Keyboard . presses ERRE [edit]
!$KEY ................ ! flush the keyboard buffer ! -------------------------------- ! you can use POKE(198,0) in C-64 ! ERRE version ! -------------------------------- REPEAT GET(K$) UNTIL K$="" PRINT("Press Y or N to continue") REPEAT GET(K$) UNTIL INSTR("YyNn",K$)<>0 ! ! with C-64 you must write a line like ! UNTIL K$="Y" OR K$="N" ! PRINT("The response was ";K$) ................. !$KEY is a directive pragma: using it GET become an equivalent to Qbasic INKEY$, otherwise it's equivalent to QBasic INPUT$(1). !$KEY is also used to mantain portability with the C-64 version of ERRE language.
Euphoria [edit]
integer key puts(1,"Your answer? (Y/N)\n") while get_key()!=-1 do end while while 1 do key = get_key() if key!=-1 and (key = 'Y' or key = 'y' or key = 'N' or key = 'n') then exit end if end while printf(1,"Your response was %s\n",key) F# [edit]
open System let rec yorn () = let rec flush () = if Console . KeyAvailable then ignore ( Console . ReadKey () ); flush () flush () printf " \n Y or N? " match Console . ReadKey () . Key with | ConsoleKey . Y -> 'Y' | ConsoleKey . N -> 'N' | _ -> yorn () printfn " \n Your choice: %c" ( yorn () ) Forth [edit]
: flush ( -- ) \ discard pending input begin key? while key drop repeat ; : y-or-n ( c-addr u -- f ) flush begin cr 2dup type key bl or \ note 1. dup [char] y = swap [char] n = over or \ note 2. if nip nip exit then drop again ; \ Note 1. KEY BL OR returns a lowercase letter in the case that an \ uppercase letter was entered, an unchanged lowercase letter in the \ case that a lowercase letter was entered, and garbage otherwise. BL \ returns the ASCII code for a space, 32, which is incidentally the \ "bit of difference" between ASCII uppercase and lowercase letters. \ Note 2. this line has the stack effect ( x -- f1 f2 ), where F1 is \ true only if x='y', and F2 is true only if x='y' OR if x='n'. \ I think these expressions aren't too clever, but they _are_ rather \ optimized for the task at hand. This might be more conventional: : y-or-n ( c-addr u -- f ) flush begin cr 2dup type key case [char] y of 2drop true exit endof [char] Y of 2drop true exit endof [char] n of 2drop false exit endof [char] N of 2drop false exit endof endcase again ; Fortran [edit]
Standard Fortran has no special I/O statements that allow asynchronous actions (such as the KeyPressed and ReadKey functions of Turbo Pascal), so input is awaited in the usual fashion and a prompt should be supplied to indicate to the reader that a response is awaited, otherwise the user will confront a blank screen with nothing happening and will have to guess what might be expected. Further, there is no scheme for knowing if impending input has been waiting in an input buffer since before the need for a question arose, so it is not possible to flush such lines before requesting the special input. Impatience at the screenface can prompt typing ahead so that the next command will be immediately available but incorrectly anticipated input will likely wreck the run, though for yes/no responses you may be rescued if such input does not conform to the required form: the bad input will be ignored and the question asked afresh. Thus, the details of the specification cannot be met via standard Fortran, though a given system may have special subroutines equivalent to KeyPressed, etc. available.
Even so, asking questions can often be useful when messing about with tests, etc., so some routines for this can help. These were devised afresh at the Culham Science Centre, so there was some language generality:
CHARACTER * 120 FUNCTION REPLY ( QUERY ) !Obtain a text in reply. Concocted by R . N . McLean ( whom God preserve ), December MM . CHARACTER * ( * ) QUERY !The question. CHARACTER * 120 TEXT !Alas, oh for proper strings. INTEGER MSG , KEYS , LSTNB !Let's hope everyone has the same type. COMMON / IOUNITS / MSG , KEYS !Orifices. WRITE ( MSG , 1 ) QUERY ( 1 : LSTNB ( QUERY )), "?" !So, splurt. 1 FORMAT ( 2 A , $ ) !A trailing text literal may not be rolled. READ ( KEYS , 1 ) TEXT !Dare not use REPLY itself. Some implementations bungle. REPLY = TEXT !So, shuffle. RETURN !Take that. END !Others interpret the reply. REAL * 8 FUNCTION REPLYN ( QUERY ) !Obtain a number in reply. Concocted by R . N . McLean ( whom God preserve ), December MM . CHARACTER * ( * ) QUERY !The question. REAL X !The answer, presumably not 42. INTEGER MSG , KEYS , LSTNB !Let's hope everyone has the same type. COMMON / IOUNITS / MSG , KEYS !Orifices. 1 WRITE ( MSG , 2 ) QUERY ( 1 : LSTNB ( QUERY )) !No trailing spaces. 2 FORMAT ( A , $ ) !The $ obviously suppresses the newline. READ ( KEYS , * , ERR = 3 ) X !Presume adequate testing for now. REPLYN = X !The value! RETURN !All done. 3 WRITE ( MSG , 4 ) !Or perhaps not. 4 FORMAT ( 'Distasteful number. Try again...' ) !All sorts of ways. GO TO 1 !My patience is unconditional. END !One way or another, a number will be secured. LOGICAL FUNCTION YEA ( QUERY ) !Obtain a Yes in reply? Concocted by R . N . McLean ( whom God preserve ), December MM . CHARACTER * ( * ) QUERY !The question. CHARACTER * 120 WHAT , REPLY !Quite so. CHARACTER * 1 C !Scratchpad. INTEGER MSG , KEYS !Let's hope everyone has the same type. COMMON / IOUNITS / MSG , KEYS !Orifices. INTEGER L !A finger. 1 WHAT = REPLY ( QUERY ) !So, get an answer. DO L = 1 , LEN ( WHAT ) !Sigh. Oh for Trim(string) C = WHAT ( L : L ) !Sniff a CHARACTER. IF ( C . NE . ' ' ) GO TO 10 !A starter? END DO !No. Try further on. WRITE ( MSG , 2 ) !Surely not. 2 FORMAT ( 'All blank?' ) !Poke. 3 WRITE ( MSG , 4 ) !Sigh. 4 FORMAT ( 'I dig it not. Try Yes/Si/Da/Oui/Ja, or No' ) GO TO 1 !Get it right, this time? 10 IF ( INDEX ( 'YySsDdOoJj' , C ) . GT . 0 ) THEN !Yes/Si/Da/Oui/Ja... YEA = . TRUE . !A decision. ELSE IF ( INDEX ( 'Nn' , C ) . GT . 0 ) THEN !No,No,Nyet,Non... YEA = . FALSE . !Even if negative. ELSE !But if unrecognised, GO TO 3 !Try again. END IF !So much for choices. RETURN !Pass the word. END !Enough of yes-beings. LOGICAL FUNCTION NAY ( QUERY ) !Perhaps this reads better. Concocted by R . N . McLean ( whom God preserve ), December MM . CHARACTER * ( * ) QUERY !The question. LOGICAL YEA !Let us hope so. NAY = . NOT . YEA ( QUERY ) !Straightforward. RETURN !Pass the inverted word. END !So much for naysayers. Usage might be something like IF (NAY("Keep the results")) CALL PURGE
FreeBASIC [edit]
' FB 1.05.0 Win64 While InKey <> "" : Wend '' flush keyboard buffer Print "Do you want to continue y/n : " ; Dim answer As String Do answer = LCase ( Inkey ) Loop Until answer = "y" OrElse answer = "n" Print answer '' echo response to console If answer = "y" Then Print "OK, continuing" Else Print "OK, finishing" End If Sleep Sample input/output:
Do you want to continue y/n : y OK, continuing
FutureBasic [edit]
void local fn DoDialog( ev as long ) CFStringRef key select ( ev ) case _windowKeyDown cls key = fn EventCharacters select ( lcase(key) ) case @"y",@"n" printf @"You pressed the \"%@\" key",key DialogEventSetBool(YES)// we handled the event end select end select end fn subclass window 1, @"Press \"Y\" or \"N\" keys", (0,0,550,400) on dialog fn DoDialog HandleEvents GlovePIE [edit]
if var.end=0 then var.end=0 debug="Press the Y key or the N key to continue:" endif if pressed(Key.Y)and var.end=0 then var.end=1 debug="You pressed the Y key." endif if pressed(Key.N)and var.end=0 then var.end=1 debug="You pressed the N key." endif Go [edit]
package main import ( "log" gc "code.google.com/p/goncurses" ) func main () { s , err := gc . Init () if err != nil { log . Fatal ( "init:" , err ) } defer gc . End () var k gc . Key for { gc . FlushInput () s . MovePrint ( 20 , 0 , "Press y/n " ) s . Refresh () switch k = s . GetChar (); k { default : continue case 'y' , 'Y' , 'n' , 'N' : } break } s . Printf ( "\nThanks for the %c!\n" , k ) s . Refresh () s . GetChar () } -
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package main // siongui.github.io/2016/04/23/go-read-yes-no-from-console import ( "fmt" "strings" ) func ask () bool { var s string fmt . Printf ( "(y/n): " ) fmt . Scan ( & s ) s = strings . TrimSpace ( s ) s = strings . ToLower ( s ) if s == "y" || s == "yes" { return true } return false } func main () { ans := ask () if ans { fmt . Println ( "yes" ) } else { fmt . Println ( "no" ) } }
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GW-BASIC [edit]
10 IF INKEY$ <> "" THEN GOTO 10: REM flush the keyboard buffer 20 PRINT "Press Y or N to continue" 30 LET k$ = INKEY$ 40 IF k$ <> "y" AND k$ <> "Y" AND k$ <> "n" AND k$ <> "N" THEN GOTO 30 50 PRINT "The response was " ; k$ Haskell [edit]
This may not be very idiomatic; it's pretty monad-oriented, and the use of do expressions makes the whole thing feel rather imperative.
import System.IO hFlushInput :: Handle -> IO () hFlushInput hdl = do r <- hReady hdl if r then do c <- hGetChar hdl hFlushInput hdl else return () yorn :: IO Char yorn = do c <- getChar if c == 'Y' || c == 'N' then return c else if c == 'y' then return 'Y' else if c == 'n' then return 'N' else yorn main :: IO () main = do hSetBuffering stdout NoBuffering putStr "Press Y or N to continue: " hSetBuffering stdin NoBuffering hSetEcho stdin False hFlushInput stdin answer <- yorn putStrLn [ answer ] Icon and Unicon [edit]
This solution works in both Icon and Unicon. It also accepts y or n.
procedure main () write ( "Response was " , getResponse ( "OK? (Y or N): " )) end procedure getResponse ( prompt ) while kbhit () do getch () # flush input writes ( prompt ) repeat if map ( answer := getch ()) == ( "y" | "n" ) then break return answer end Inform 7 [edit]
Keyboard input goes through a virtual machine that's only required to provide blocking input operations, so flushing the buffer isn't possible.
Inform 7 has a built-in function to ask the user for yes-or-no input, but it requires them to press enter afterward:
Qwantz is a room. When play begins: say "A wizard has turned you into a whale. Is this awesome (Y/N)? "; if the player consents, say "Awesome!"; end the story. To read a single key without waiting for enter, we can redefine the function by including a snippet of Inform 6 code:
To decide whether player consents: (- ( YesOrNoKey ()) -). Include (- [ YesOrNoKey ch ; do { ch = VM_KeyChar (); } until ( ch == 'y' or 'Y' or 'n' or 'N' ); return ch == 'y' or 'Y' ; ]; -). JavaScript [edit]
Here's a synchronous ES6 implementation. The synchronous code must be executed in an async function definition. In this example, `wait_key` returns the key pressed and `done` must be called decouple the listening to stdin and end the process. The example pauses for a second to show that the keys pressed before `wait_key` is called are not heard.
const readline = require ( 'readline' ); readline . emitKeypressEvents ( process . stdin ); process . stdin . setRawMode ( true ); var wait_key = async function () { return await new Promise ( function ( resolve , reject ) { var key_listen = function ( str , key ) { process . stdin . removeListener ( 'keypress' , key_listen ); resolve ( str ); } process . stdin . on ( 'keypress' , key_listen ); }); } var done = function () { process . exit (); } var go = async function () { do { console . log ( 'Press any key...' ); var key = await wait_key (); console . log ( "Key pressed is" , key ); await new Promise ( function ( resolve ) { setTimeout ( resolve , 1000 ); }); } while ( key != 'y' ); done (); } go (); Here's how you can asynchronously read a single character in Node.js, using the keypress package. This does not seem to be possible to do synchronously in Node.js or at all in the SpiderMonkey shell.
var keypress = require ( 'keypress' ); keypress ( process . stdin ); process . stdin . on ( 'keypress' , function ( ch , key ) { if ( key && ( key . name === 'y' || key . name === 'n' )) { console . log ( 'Reply:' + key . name ); } }); process . stdin . setRawMode ( true ); process . stdin . resume (); Using DOM events.
document . body . addEventListener ( 'keyup' , function ( e ) { var key = String . fromCharCode ( e . keyCode ). toLowerCase (); if ( key === 'y' || key === 'n' ) { console . log ( 'response is: ' + key ); } }, false ); Julia [edit]
Uses the Gtk library.
using Gtk . ShortNames function keypresswindow () # This code creates the Gtk widgets on the screen. txt = "Type Y or N" win = Window ( "Keypress Test" , 250 , 30 ) |> ( Frame () |> (( vbox = Box ( :v )) |> ( lab = Label ( txt )))) # this is the keystroke processing code, a function and a callback for the function. function keycall ( w , event ) ch = Char ( event . keyval ) set_gtk_property! ( lab , :label , ch in ( 'n' , 'N' , 'y' , 'Y' ) ? "You hit the $ch key." : txt ) end Gtk . signal_connect ( keycall , win , "key-press-event" ) # this code sets up a proper exit when the widow is closed. c = Condition () endit ( w ) = notify ( c ) Gtk . signal_connect ( endit , win , :destroy ) Gtk . showall ( win ) wait ( c ) end keypresswindow () Kotlin [edit]
// version 1.0.6 import java . awt . event . KeyAdapter import java . awt . event . KeyEvent import javax . swing . JFrame import javax . swing . SwingUtilities class Test : JFrame () { init { while ( System . `in` . available () > 0 ) System . `in` . read () println ( "Do you want to quit Y/N" ) addKeyListener ( object : KeyAdapter () { override fun keyPressed ( e : KeyEvent ) { if ( e . keyCode == KeyEvent . VK_Y ) { println ( "OK, quitting" ) quit () } else if ( e . keyCode == KeyEvent . VK_N ) { println ( "N was pressed but the program is about to end anyway" ) quit () } else { println ( "Only Y/N are acceptable, please try again" ) } } }) } private fun quit () { isVisible = false dispose () System . exit ( 0 ) } } fun main ( args : Array < String > ) { SwingUtilities . invokeLater { val f = Test () f . isFocusable = true f . isVisible = true } } Liberty BASIC [edit]
nomainwin open "Y/N" for graphics_nsb_nf as #1 #1 "trapclose Quit" #1 "down;setfocus;when characterInput KeyCheck" #1 "place 10 50;\Press Y or N" Inkey$="" wait sub KeyCheck hndle$,k$ k$=upper$(k$) #hndle$ "cls;place 10 50" select case k$ case "Y" #hndle$ "\ Yes" case "N" #hndle$ "\No" case else #hndle$ "\Incorrect input. Press Y or N" end select end sub sub Quit hndle$ close #hndle$ end end sub LiveCode [edit]
In the Card script, add a handler for the OpenCard event, putting empty into the text field.
In the text field, put the following in its code
on KeyDown k if toUpper(k) is among the items of "Y,N" then answer "Thanks for your response" else answer "You need to enter Y or N" end if put empty into me end KeyDown n.b. This sort of confirmation in GUI apps is usually presented as a dialog box with Yes/No buttons, which automatically handles keyboard input.
Logo [edit]
to yorn type [Press Y or N to continue: ] local "clear make "clear readchars 0 ; clear input buffer local "yorn do.until [make "yorn readchar] [or equal? :yorn "Y equal? :yorn "N] print :yorn output :yorn end M2000 Interpreter [edit]
Simple Loop using Key$ [edit]
If keyboard is Greek the we have to change to English. Other examples use Keyboard codes.
Module Simple { \\ a small modification from BBC BASIC entry REPEAT {} UNTIL INKEY$ = "" PRINT "Press Y or N to continue" REPEAT { k$ =Ucase$(Key$) } UNTIL K$="Y" OR k$="N" PRINT "The response was "; k$ } Simple Use a Function to return keypress and by reference return value [edit]
Module Checkit { Function GetYN$ (&Ret) { const Y=0x59 const N=0x4E Ret=False Do { if keypress(Y) then Ret=True : exit if keypress(N) then exit drop$=inkey$ } Always K$=key$ do {} until filter$(Inkey$,k$)="" =Ucase$(K$) } keyboard "abcde" ' feed keyboard (inkey$ get these characters) Y=0 Print "Your answer (Y/N):"; GetYN$(&Y) Print Y } Checkit Using Thread to read/write Keyboard buffer [edit]
We use a thread, using after, for one run, after 10ms, when Input wait for keypress. So when call to GetYN module exit has Y or N with Enter to keyboard. Now Input finish.
Threads runs in same namespace as the module they created. So module name and Y variable are visible.Module GetYN can't read parent module variables, except M which declared as GLOBAL. After 500ms N is returned.
Using Profiler and Print Timecount we get the real duration (using high resolution timer), of response.
Module CheckisToo { Module GetYN (&Ret) { const Y=0x59 const N=0x4E Ret=False Do { If M>50 then Keyboard "N" : exit if keypress(Y) then Ret=True : exit if keypress(N) then exit drop$=inkey$ \\ ensure thread MM run using wait wait 1 } Always Keyboard Ucase$(Key$)+Chr$(13) } keyboard "abcde" Y=0 Global M=0 Thread { M++ } as MM interval 10 While Inkey$<>"" {} After 10 { Module GetYN &Y } Profiler Input "Your answer (Y/N):", A$ Print timecount Print Y, M Threads Erase } CheckisToo Using User Form (GUI) [edit]
Module UseUIForm { Const Y=0x59, N=0x4E, Center=2 Ret=False Declare Form1 form Layer Form1 { Window 22, 8000, 4000; Cls #333333,0 Cursor 0, Height/2 Report Center, "Press (Y/N)" } Function form1.Keydown { Read New &key, &shiftKey IF key=Y then ret=True : Method Form1, "CloseNow" If key=N Then Method Form1, "CloseNow" } Method Form1, "Show", 1 ' modal show Print Ret Declare Form1 Nothing } UseUIForm Mathematica/Wolfram Language [edit]
CreateDialog [ TextCell [ "Yes or no?[Y/N]" ], NotebookEventActions -> { "KeyDown" :> Switch [ ToUpperCase @ CurrentValue [ "EventKey" ], "Y" , Print [ "You said yes" ]; DialogReturn [], "N" , Print [ "You said no" ]; DialogReturn [] ]}]; Microsoft Small Basic [edit]
Submitted by: AykayayCiti (Earl L. Montgomery) on Mar 19, 2018. Once you hit a key a separate dialog box will appear. Place them side by side to see the results.
'From: 'Andy Oneill, 2-6-2015, "Small Basic: Key Input, '" TechNet, https://social.technet.microsoft.com/wiki/contents/articles/29850.small-basic-key-input.aspx, accessed 3-19-2018 GraphicsWindow . DrawText ( 10 , 10 , "Hit any key to dump." ) GraphicsWindow . KeyDown = OnKeyDown Sub OnKeyDown TextWindow . WriteLine ( GraphicsWindow . LastKey ) EndSub MiniScript [edit]
Access to hardware like the keyboard is very dependent on the host app, but here's a version that works with MiniMicro, a standardized MiniScript virtual machine.
// flush the keyboard while key . available key . get end while // and now prompt and wait for Y or N print "Press Y or N:" k = "" while k != "Y" and k != "N" k = key . get . upper end while print "You pressed: " + k MUMPS [edit]
Version from terminal shown below.
for read !,"Enter Y or N to continue: ",input quit:input?1(1"Y",1"y",1"N",1"n") Enter Y or N to continue: JEnter Y or N to continue: YES Enter Y or N to continue: no Enter Y or N to continue: N
SAMPLES>
NetRexx [edit]
/* NetRexx */ options replace format comments java crossref savelog symbols binary Say 'Please enter Y or N' parse ask c Select when c= 'Y' Then Say 'YES' when c= 'N' Then Say 'NO' otherwise Say 'Undecided' End Nim [edit]
Using "gintro" bindings to Gtk3.
import strformat import gintro /[ glib , gobject , gtk , gio ] import gintro / gdk except Window #--------------------------------------------------------------------------------------------------- proc onKeyPress ( window : ApplicationWindow ; event : Event ; label : Label ): bool = var keyval : int if not event . getKeyval ( keyval ): return false if keyval in [ ord ( 'n' ), ord ( 'y' ) ] : label . setText ( & "You pressed key '{chr(keyval)}'" ) result = true #--------------------------------------------------------------------------------------------------- proc activate ( app : Application ) = ## Activate the application. let window = app . newApplicationWindow () window . setTitle ( "Y/N response" ) let hbox = newBox ( Orientation . horizontal , 0 ) window . add ( hbox ) let vbox = newBox ( Orientation . vertical , 10 ) hbox . packStart ( vbox , true , true , 20 ) let label1 = newLabel ( " Press 'y' or 'n' key " ) vbox . packStart ( label1 , true , true , 5 ) let label2 = newLabel () vbox . packStart ( label2 , true , true , 5 ) discard window . connect ( "key-press-event" , onKeyPress , label2 ) window . showAll () #——————————————————————————————————————————————————————————————————————————————————————————————————— let app = newApplication ( Application , "Rosetta.YNResponse" ) discard app . connect ( "activate" , activate ) discard app . run () NS-HUBASIC [edit]
10 PRINT "PRESS Y OR N TO CONTINUE." 20 IF INKEY$<>"Y" AND INKEY$<>"N" THEN GOTO 20 30 PRINT "THE RESPONSE WAS ";INKEY$;"." OCaml [edit]
Unix module, exposing POSIX interfaces like termios, is normally bundled with any standard OCaml distribution. Utilizing termios is the solution many other language examples here went with.
OCaml needs to link to the bundled unix archives correctly in order to compile / run code that uses definitions within the module. To do this with the plain OCaml toolchain, remember to add the library archive to the commandline like so:
ocaml unix.cma <yourfile.ml> interpreted
ocamlc -o <progname> unix.cma <yourfile.ml> bytecode executable
ocamlopt -o <progname> unix.cmxa <yourfile.ml> native executable
Here we define some helper functions that we'll use:
let attrs = Unix . ( tcgetattr stdin ) let buf = Bytes . create 1 let prompt switch = Unix . ( tcsetattr stdin TCSAFLUSH ) @@ if switch then { attrs with c_icanon = false } else attrs let getchar () = let len = Unix . ( read stdin ) buf 0 1 in if len = 0 then raise End_of_file else Bytes . get buf 0 Now the main program:
let rec loop () = print_string "Prompt? [Y/N]: " ; flush stdout ; loop @@ print_endline @@ match getchar () with | 'n' | 'N' -> raise Exit | 'y' | 'Y' -> ": Ok." | _ -> ": Invalid." let _ = try loop @@ prompt true with Exit | End_of_file -> prompt false Oforth [edit]
import: console : YorN | c | System.Console flush doWhile: [ System.Console receiveChar toUpper ->c c 'Y' <> c 'N' <> and ] c ; OpenEdge/Progress [edit]
DEF VAR lanswer AS LOGICAL INITIAL ? . DO WHILE lanswer = ? : READKEY . IF CHR ( LASTKEY ) = "n" OR CHR ( LASTKEY ) = "y" THEN lanswer = CHR ( LASTKEY ) = "y" . END . MESSAGE lanswer VIEW-AS ALERT-BOX . PARI/GP [edit]
GP's input is not able to read an unbuffered single character, so one must use PARI where the solution is identical to that of C.
Pascal [edit]
Program ObtainYN ; uses crt ; var key : char ; begin write ( 'Your answer? (Y/N): ' ) ; repeat key := readkey ; until ( key in [ 'Y' , 'y' , 'N' , 'n' ]) ; writeln ; writeln ( 'Your answer was: ' , key ) ; end . Output:
% ./ObtainYN Your answer? (Y/N): Your answer was: y
Perl [edit]
use Term::ReadKey ; ReadMode 4 ; # change to raw input mode my $key = '' ; while ( $key !~ /(Y|N)/i ) { 1 while defined ReadKey - 1 ; # discard any previous input print "Type Y/N: " ; $key = ReadKey 0 ; # read a single character print "$key\n" ; } ReadMode 0 ; # reset the terminal to normal mode print "\nYou typed: $key\n" ; Phix [edit]
For 1970s-style character console (/beginner) applications:
integer key while get_key ()!=- 1 do end while -- flush puts ( 1 , "Your answer? (Y/N)" ) while 1 do key = upper ( get_key ()) if find ( key , "YN" ) then exit end if end while printf ( 1 , "\nYour response was %s\n" , key )
For GUI (graphical user interface) applications, use something more like this:
function key_cb ( Ihandle /*ih*/ , atom c ) if lower ( c )= 'y' then y_keyed () end if if lower ( c )= 'n' then n_keyed () end if return IUP_CONTINUE end function IupSetCallback ( dlg , "K_ANY" , Icallback ( "key_cb" ))
See Keyboard_macros#Phix or Conway's_Game_of_Life#Phix for a more complete example
PicoLisp [edit]
(de yesno () (loop (NIL (uppc (key))) (T (= "Y" @) T) (T (= "N" @)) ) ) PL/I [edit]
yn: Proc Options(main): Dcl sysin stream input; Dcl sysprint stream output; Dcl c Char(1); Put Skip List('Please enter Y or N'); Get Edit(c)(a(1)); Select(c); When('Y','y','J','j') Put Skip List('YES'); When('N','n') Put Skip List('NO'); Otherwise Put Skip List('Undecided?'); End; End; PowerShell [edit]
This is for console use only. The ISE is geared for a different type of input.
do { $keyPress = [System.Console] :: ReadKey () } until ( $keyPress . Key -eq "Y" -or $keyPress . Key -eq "N" ) $keyPress | Format-Table -AutoSize If the user pressed the "Y" key...
KeyChar Key Modifiers ------- --- --------- y Y 0
If the user pressed the "N" key...
KeyChar Key Modifiers ------- --- --------- n N 0
PureBasic [edit]
Inkey() returns the character string of the key which is being pressed at the time.
PrintN ( "Press Y or N to continue" ) Repeat ; Get the key being pressed , or a empty string . Key$ = UCase ( Inkey ()) ; ; To Reduce the problems with an active loop ; a Delay ( 1 ) will release the CPU for the rest ; of this quanta if no key where pressed . Delay ( 1 ) Until Key$ = "Y" Or Key$ = "N" PrintN ( "The response was " + Key$ ) Python [edit]
#!/usr/bin/env python try : from msvcrt import getch except ImportError : def getch (): import sys , tty , termios fd = sys . stdin . fileno () old_settings = termios . tcgetattr ( fd ) try : tty . setraw ( sys . stdin . fileno ()) ch = sys . stdin . read ( 1 ) finally : termios . tcsetattr ( fd , termios . TCSADRAIN , old_settings ) return ch print "Press Y or N to continue" while True : char = getch () if char . lower () in ( "y" , "n" ): print char break #!/usr/bin/env python # -*- coding: utf-8 -*- from curses import wrapper # # def main ( stdscr ): # const #y = ord("y") #n = ord("n") while True : # keyboard input interceptor|listener #window.nodelay(yes) # - If yes is 1, getch() will be non-blocking. # return char code #kb_Inpt = stdscr.getch() # return string kb_Inpt = stdscr . getkey () #if kb_Inpt == (y or n): if kb_Inpt . lower () == ( 'y' or 'n' ): break return None # return None # #*** unit test ***# if __name__ == "__main__" : # wrapper ( main ) QB64 [edit]
CBTJD: 2020/03/15
WHILE INKEY$ <> "" : WEND ' Flushes keyboard buffer. PRINT "Do you want to continue? (Y/N)" DO k$ = UCASE$ ( INKEY$ ) ' Forces key response to upper case. LOOP UNTIL k$ = "Y" OR k$ = "N" PRINT "You pressed " + CHR$ ( 34 ) + k$ + CHR$ ( 34 ) + "." ' CHR$(34) prints quotation marks. QUACKASM [edit]
Note: The following is not a full program (it is only a subroutine, using standard calling conventions), nor does it flush the keyboard buffer (there is no standard way to do this in QUACKVM; it may be possible using extensions, but none are currently defined).
; Stores result in cell 2; 1 if yes, 0 if no. :YORN PRINT YORNMSG :YORN1 INPUT >2 AND *2,$5F,'Y >2 /YORN2 AND *2,,'N \YORN1 :YORN2 PRINTC *2 PRINTC 13 AND *2,1 >2 RETURN :YORNMSG " (Y/N)? \ Racket [edit]
#lang racket ;; GUI version ( require racket/gui ) ( message-box "Yes/No example" "Yes or no?" #f ' ( yes-no )) ;; Text version, via stty ( define stty ( let ([ exe ( find-executable-path "stty" )]) ( λ args ( void ( apply system* exe args ))))) ( define tty-settings ( string-trim ( with-output-to-string ( λ () ( stty "-g" ))))) ( printf "Yes or no? " ) ( flush-output ) ( stty "-icanon" "-echo" "min" "1" ) ( let loop () ( when ( char-ready? ) ( loop ))) ( let loop () ( define ch ( read-char )) ( case ( char-downcase ch ) [( #\y #\Y #\n #\N ) ( displayln ch ) ( if ( memq ch ' ( #\y #\Y )) ' yes ' no )] [ else ( loop )])) ( stty tty-settings ) Raku [edit]
(formerly Perl 6)
my $TTY = open("/dev/tty"); sub prompt-char($prompt) { ENTER shell "stty raw -echo min 1 time 1"; LEAVE shell "stty sane"; print $prompt; $TTY.read(1).decode('latin1'); } say so prompt-char("Y or N? ") ~~ /:i y/; REXX [edit]
version for all classic REXXes [edit]
This version works with all classic REXXes.
REXX (in general) requires the user to press the ENTER key after entering text.
This is because the original (IBM) REXX was designed and written for a system when all I/O to a user's terminal screen was
in block mode and required the user to press one of the following before any data was sent to the computer:
- the ENTER key
- a PF (program function key)
- a PA (program assist key)
- the ATTN (attention) key
- possibly some other special key(s)
Note that the above keys may have different names on terminals that emulate an IBM 3270 type terminal (block mode terminals).
Some older Classic REXX interpreters have a keyboard read subroutine (BIF) so that the program can read keyboard keys as
they are pressed (see the other versions below).
/*REXX program tests for a Y or N key when entered from keyboard after a prompt.*/ do queued () ; pull ; end /*flush the stack if anything is queued*/ prompt = 'Please enter Y or N for verification:' /*this is the PROMPT message.*/ do until pos (ans, 'NY' )\== 0 & length (ans)== 1 /*keep looking for a Y or N answer.*/ say ; say prompt /*display blank line; display prompt. */ pull ans /*get the answer(s) and uppercase it.*/ ans= space (ans, 0 ) /*elide all blanks. */ end /*until*/ /*stick a fork in it, we're all done. */ version 1 for PC/REXX and Personal REXX [edit]
This version of a REXX program works with PC/REXX and Personal REXX.
/*REXX program tests for a Y or N key when entered from keyboard after a prompt.*/ prompt = 'Please enter Y or N for verification:' /*this is the PROMPT message.*/ do until pos (ans, 'NYny' ) \== 0 /*keep prompting until answer= Y N y n */ say ; say prompt /*display blank line; display prompt. */ ans=inKey( 'wait' ) /*get the answer(s) from the terminal. */ end /*until*/ /*stick a fork in it, we're all done. */ version 2 for PC/REXX and Personal REXX [edit]
This version is the same as above, but has a more idiomatic technique for testing the response.
/*REXX program tests for a Y or N key when entered from keyboard after a prompt.*/ prompt = 'Please enter Y or N for verification:' /*this is the PROMPT message.*/ do until pos (ans, 'NY' )\== 0 /*keep prompting 'til user answers Y│N */ say ; say prompt /*display blank line; display prompt. */ ans=inKey( 'wait' ) ; upper ans /*get the answer(s); and uppercase it.*/ end /*until*/ /*stick a fork in it, we're all done. */ Ring [edit]
while true give c if c = "Y" see "You said yes!" + nl but c = "N" see "You said no!" + nl else see "Try again!" + nl ok end Ruby [edit]
def yesno begin system ( "stty raw -echo" ) str = STDIN . getc ensure system ( "stty -raw echo" ) end if str == "Y" return true elsif str == "N" return false else raise "Invalid character." end end Ruby provides the io/console module since version 2.0:
require 'io/console' def yesno case $stdin . getch when "Y" then true when "N" then false else raise "Invalid character." end end Run BASIC [edit]
[loop] cls ' Clear screen html "Click Y or N" ' no other options button #y, "Y", [Y] ' they either click [Y] button #n, "N", [N] ' or they click [N] html "<br>";msg$ ' print message showing what they entered wait [Y] msg$ = "You entered [Y]es": goto [loop] [N] msg$ = "You entered [N]o" : goto [loop] Rust [edit]
//cargo-deps: ncurses extern crate ncurses ; use ncurses::* ; fn main () { initscr (); loop { printw ( "Yes or no? " ); refresh (); match getch () as u8 as char { 'Y' | 'y' => { printw ( "You said yes!" );}, 'N' | 'n' => { printw ( "You said no!" );}, _ => { printw ( "Try again! \n " ); continue ;}, } break } refresh (); endwin (); } Scala [edit]
println ( if ( scala . io . StdIn . readBoolean ) "Yes typed." else "Something else." ) import java . io . InputStreamReader val in = new InputStreamReader ( System . in ) if ( Seq ( 121 , 89 , 110 , 78 ). contains ( in . read ()) ) { println ( "Yes|No" )} else { println ( "other" )} import scala . io .{ Source , BufferedSource } val kbd_In : BufferedSource = Source . stdin //kbd_In.next() //res?: Char = 'y' not :String = "y" if ( Seq ( 'y' , 'Y' , 'n' , 'Y' ). contains ( kbd_In . next ()) ) { println ( "Typed y|Y|n|N" )} else { println ( "other key" )} Seed7 [edit]
$ include "seed7_05.s7i"; include "keybd.s7i"; const func boolean: yesOrNo (in string: prompt) is func result var boolean: yes is FALSE; local var char: answer is ' '; begin while keypressed(KEYBOARD) do ignore(getc(KEYBOARD)); end while; write(prompt); repeat answer := lower(getc(KEYBOARD)); until answer in {'y', 'n'}; yes := answer = 'y'; end func; const proc: main is func begin writeln(yesOrNo("Press Y or N to continue ")); end func; Sidef [edit]
func prompt_yn { static rk = frequire ( 'Term::ReadKey' ); rk . ReadMode ( 4 ); # change to raw input mode var key = '' ; while ( key !~ /[yn]/i ) { while ( rk . ReadKey ( - 1 ) != nil ) {}; # discard any previous input print "Type Y/N: " ; say ( key = rk . ReadKey ( 0 )); # read a single character } rk . ReadMode ( 0 ); # reset the terminal to normal mode return key . uc ; } var key = prompt_yn (); say "You typed: #{ key } " ; Type Y/N: a Type Y/N: b Type Y/N: c Type Y/N: y You typed: Y
Tcl [edit]
Using the console (expects U*Xish stty)
proc yesno {{ message "Press Y or N to continue" }} { fconfigure stdin -blocking 0 exec stty raw read stdin ; # flush puts -nonewline "${message}: " flush stdout while { ! [ eof stdin]} { set c [ string tolower [ read stdin 1 ]] if { $c eq "y" || $c eq "n" } break } puts [ string toupper $c ] exec stty -raw fconfigure stdin -blocking 1 return [expr { $c eq "y" }] } set yn [ yesno "Do you like programming (Y/N)" ] Without a console (answer in the global variable yn; this should work in any GUI for which there is a TCL):
proc yesno { message } { toplevel .msg pack [ label .msg.l -text "$message\n (type Y/N)?" ] set ::yn "" bind .msg <Key-y> {set ::yn "Y" } bind .msg <Key-n> {set ::yn "N" } vwait ::yn destroy .msg } yesno "Do you like programming?" TXR [edit]
This works not only on Unix-like platforms, but also on Microsoft Windows, because TXR is ported to Windows using a modified version of Cygwin.
(with-resources ((tio-orig (tcgetattr) (tcsetattr tio-orig))) (let ((tio (copy tio-orig))) tio.(go-raw) (tcsetattr tio tcsaflush) ;; third arg optional, defaults to tcsadrain (whilet ((k (get-char)) ((not (member k '(#\y #\n #\Y #\N)))))))) The go-raw method on the termios structure only manipulates the structure contents; tcsetattr pushes it down to the TTY driver.
go-raw is defined in the TXR standard library like this:
(defmeth termios go-raw (tio) tio.(clear-iflags ignbrk brkint parmrk istrip inlcr igncr icrnl ixon) tio.(clear-oflags opost) tio.(clear-cflags csize parenb) tio.(clear-lflags echo echonl icanon isig) (if (boundp 'iexten) tio.(clear-lflags iexten)) tio.(set-cflags cs8) (set tio.[cc vmin] 1) (set tio.[cc vtime] 0)) UNIX Shell [edit]
getkey() { local stty = " $(stty -g) " trap "stty $stty ; trap SIGINT; return 128" SIGINT stty cbreak -echo local key while true; do key = $(dd count = 1 2>/dev/null) || return $? if [ -z " $1 " ] || [[ " $key " == [ $1 ] ]] ; then break fi done stty $stty echo " $key " return 0 } yorn() { echo -n " ${ 1 :- Press Y or N to continue: } " >& 2 local yorn = " $(getkey YyNn) " || return $? case " $yorn " in [Yy]) echo >& 2 Y; return 0 ;; [Nn]) echo >& 2 N; return 1 ;; esac } Cleaner version using bash built-ins
#!/bin/bash yorn() { echo -n " ${ 1 :- Press Y or N to continue: } " shopt -s nocasematch until [[ " $ans " == [yn] ]] do read -s -n1 ans done echo " $ans " shopt -u nocasematch } yorn VB-DOS [edit]
OPTION EXPLICIT DIM T AS INTEGER T = MSGBOX ( "Click on yes or no" , 4 , "Option" ) PRINT "The response is " ; IF T = 6 THEN PRINT "yes" ; ELSE PRINT "no" ; PRINT "." END Vedit macro language [edit]
Key_Purge() // flush keyboard buffer do { #1 = Get_Key("Are you sure? (Y/N): ") // prompt for a key #1 &= 0xdf // to upper case } while (#1 != 'Y' && #1 != 'N') V (Vlang) [edit]
import term.ui as tui struct App { mut: tui &tui.Context = 0 } fn event(e &tui.Event, x voidptr) { mut app := &App(x) app.tui.clear() app.tui.set_cursor_position(0, 0) app.tui.write('V term.input event viewer (type `y`, `Y`, `n`, or `N` to exit)\n\n') if e.typ == .key_down { mut cap := '' if !e.modifiers.is_empty() && e.modifiers.has(.shift) { cap = 'capital' } match e.code { .y { app.tui.write('You typed $cap y') } .n { app.tui.write('You typed $cap n') } else { app.tui.write("You didn't type n or y") } } } app.tui.flush() if e.typ == .key_down && (e.code == .y || e.code==.n) { exit(0) } } fn main() { mut app := &App{} app.tui = tui.init( user_data: app event_fn: event window_title: 'V term.ui event viewer' hide_cursor: true capture_events: true frame_rate: 60 use_alternate_buffer: false ) println('V term.input event viewer (type `y`, `Y`, `n`, or `N` to exit)\n\n') app.tui.run()? } Wee Basic [edit]
print 1 "Enter Y for yes, or N for no. (not case sensitive)" let loop=0 let keycode=0 while loop=0 let keycode=key() if keycode=121 let response$="y" let loop=1 elseif keycode=89 let response$="Y" let loop=1 elseif keycode=110 let response$="n" let loop=1 elseif keycode=78 let response$="N" let loop=1 endif wend print 1 "You entered"+response$ end Wren [edit]
import "io" for Stdin , Stdout Stdin . isRaw = true // input is neither echoed nor buffered in this mode System . print ( "Press Y or N" ) Stdout . flush () var byte while (( byte = Stdin . readByte ()) && ! "YNyn" . bytes . contains ( byte )) {} var yn = String . fromByte ( byte ) System . print ( yn ) Stdin . isRaw = false Sample run:
Press Y or N y
XPL0 [edit]
include c:\cxpl\codes; \intrinsic 'code' declarations loop [OpenI(1); \flush any pending keystroke case ChIn(1) of \get keystroke ^Y,^y: Text(0, "yes"); ^N,^n: Text(0, "no"); $1B: quit \Esc key terminates program other ChOut(0, 7\bel\); CrLf(0); ] Z80 Assembly [edit]
This simple template can be CALLed to wait for a Y/N response and act based on that. This particular template is limited in that the code that gets executed based on the response can't be changed at runtime (at least not without self-modifying code.)
wait_for_key_input: call & BB06 ;bios call, waits until key is pressed, returns key's ASCII code into A and % 11011111 ;converts to upper case cp ' Y ' jp z , User_Chose_Yes cp ' N ' jp z , User_Chose_No jp wait_for_key_input User_Chose_Yes: ;your code for what happens when the user types "Y" goes here ret User_Chose_No: ;your code for what happens when the user types "N" goes here ret mckinleygivernevends.blogspot.com
Source: https://rosettacode.org/wiki/Keyboard_input/Obtain_a_Y_or_N_response
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