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digitalmars.D.learn - undefined identifier getch()

reply Nrgyzer <nrgyzer gmail.com> writes:
Hey guys,

I'm writing a console based tool for windows. To receive the users input, I
try to use getch() but the compiler always says "Error: undefined identifier
getch". When I use getchar() it compiles successfully, but getchar() doesn't
returns after a single input.

Is there any equivalent version in D for getch?

Thanks & regards...
Dec 08 2010
next sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 08 Dec 2010 06:06:18 -0500, Nrgyzer <nrgyzer gmail.com> wrote:


 Hey guys,

 I'm writing a console based tool for windows. To receive the users  
 input, I
 try to use getch() but the compiler always says "Error: undefined  
 identifier
 getch". When I use getchar() it compiles successfully, but getchar()  
 doesn't
 returns after a single input.

 Is there any equivalent version in D for getch?

 Thanks & regards...


Just a note, dmd on windows does not use Microsoft's C library, it uses  
Digital Mars'.  Therefore, any C functions that are not part of the  
platform SDK are not available in D.

To see what DMC supports, look here:  
http://www.digitalmars.com/rtl/rtl.html

-Steve
Dec 08 2010
parent reply Nrgyzer <nrgyzer gmail.com> writes:
Okay, but what function can I use to get the pressed key?
kbhit/_kbhit seems to do what I want, but hwo can I use it in D? I
always get the error, that kbhit (or similar functions) are not
available.

import std.stdio;
import std.c.stdlib;
import std.c.windows.windows;

void main(string[] args) {
	kbhit();
	_kbhit();
}
Dec 08 2010
next sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 08 Dec 2010 08:25:38 -0500, Nrgyzer <nrgyzer gmail.com> wrote:


 Okay, but what function can I use to get the pressed key?
 kbhit/_kbhit seems to do what I want, but hwo can I use it in D? I
 always get the error, that kbhit (or similar functions) are not
 available.

 import std.stdio;
 import std.c.stdlib;
 import std.c.windows.windows;


extern(C) int kbhit(void);


 void main(string[] args) {
 	kbhit();
 }


In order to call a C function you have to declare it.  That's all  
std.c.windows.windows does.  Just not all the functions are declared.

Plus, I saw that getch is in that header as well...



-Steve
Dec 08 2010
next sibling parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 08 Dec 2010 08:57:40 -0500, Steven Schveighoffer  
<schveiguy yahoo.com> wrote:


 extern(C) int kbhit(void);



Um... sorry, D doesn't support void args (copy-paste problem):

extern(C) int kbhit();

-Steve
Dec 08 2010
prev sibling parent Nrgyzer <nrgyzer gmail.com> writes:
Great, thanks :)
Dec 08 2010
prev sibling parent Stewart Gordon <smjg_1998 yahoo.com> writes:
On 08/12/2010 13:25, Nrgyzer wrote:

 Okay, but what function can I use to get the pressed key?
 kbhit/_kbhit seems to do what I want, but hwo can I use it in D? I
 always get the error, that kbhit (or similar functions) are not
 available.


<snip>

kbhit just tests whether there's a keystroke waiting in the keyboard 
buffer.  It doesn't identify the key pressed.

If you want to wait for the user to press a key, use getch.

If you want to test whether the user has pressed a key, use kbhit, then 
use getch to determine what key was pressed.

For some reason, this seems to work reliably only on ASCII character 
keys, backspace, tab and carriage return.  But this might be partly due 
to bugs in the DM implementation.

Stewart.
Dec 08 2010
prev sibling parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
On 08/12/2010 11:06, Nrgyzer wrote:

 Hey guys,

 I'm writing a console based tool for windows. To receive the users input, I
 try to use getch() but the compiler always says "Error: undefined identifier
 getch". When I use getchar() it compiles successfully, but getchar() doesn't
 returns after a single input.


Under DMD 1, getch is declared in std.c.stdio.  So import that.

Under DMD 2, I don't know why it isn't there.  But you just need to add 
this declaration:

extern (C) int getch();


 Is there any equivalent version in D for getch?


D doesn't have its own API for console operations besides 
stdin/stdout/stderr stuff.  I guess it wasn't worth creating one partly 
because it would be a load of pointless wrappers around C functions, and 
partly because in these days where everyone uses GUI-based software 
they're not used as much.

Stewart.
Dec 08 2010
parent Christopher Nicholson-Sauls <ibisbasenji gmail.com> writes:
On 12/08/10 08:53, Stewart Gordon wrote:

 On 08/12/2010 11:06, Nrgyzer wrote:

 Hey guys,

 I'm writing a console based tool for windows. To receive the users
 input, I
 try to use getch() but the compiler always says "Error: undefined
 identifier
 getch". When I use getchar() it compiles successfully, but getchar()
 doesn't
 returns after a single input.


 
 Under DMD 1, getch is declared in std.c.stdio.  So import that.
 
 Under DMD 2, I don't know why it isn't there.  But you just need to add
 this declaration:
 
 extern (C) int getch();
 

 Is there any equivalent version in D for getch?


 
 D doesn't have its own API for console operations besides
 stdin/stdout/stderr stuff.  I guess it wasn't worth creating one partly
 because it would be a load of pointless wrappers around C functions, and
 partly because in these days where everyone uses GUI-based software
 they're not used as much.
 
 Stewart.


Might it be useful to provide something a la conio.h?  It doesn't have
to be part of the standard, really (conio isn't a C standard, as I
recall).  I do a bit of console oriented work myself, as I mostly write
tools, back-end programs, etc.

Yes, it'd be mostly C wrappers, but it's never stopped us before.

-- Chris N-S
Dec 08 2010