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digitalmars.D.learn - Debug output functions

reply Wouter Verhelst <wouter grep.be> writes:
So, I wanted to create a number of functions that would call write(),
writef(), writefln(), or writeln() with whatever arguments they were
given, but only if the user had used a 'enable debugging' command-line
option (or some such).

What I first did was this:

module debugout;

int debuglevel;

void set_level(int level) {
	debuglevel = level;
}

auto tdebug(func)(int level, ...) {
	va_list va;
	va_start(va, level);
	if(debuglevel <= level) {
		return func(va);
	}
	va_end(va);
}

alias tdebug!(write) wdebug;
alias tdebug!(writef) wdebugf;
(... and so on...)

but that didn't work:

debugout.d(20): Error: template instance tdebug!(write) tdebug!(write) does not
match template declaration tdebug(func)

I had a short look at http://dlang.org/variadic-function-templates.html
which would seem to be a somewhat better way of implementing this, but I
can't figure out how exactly I should go forward, then.

I do believe that something like the following would do what I want:

auto wdebug(level, ...) {
	va_list va;
	va_start(va, level);
	writefx(stdout, ???, va);
	va_end(va);
}

except the va_list stuff doesn't seem to be necessary, I don't know what
to put in place of the "???", and I'd have to write this four times
rather than being able to template it four times.

How should I do this instead?

-- 
The volume of a pizza of thickness a and radius z can be described by
the following formula:

pi zz a
Jul 02 2012
next sibling parent "nazriel" <nazriel6969 gmail.com> writes:
On Tuesday, 3 July 2012 at 03:15:02 UTC, Wouter Verhelst wrote:

 So, I wanted to create a number of functions that would call 
 write(),
 writef(), writefln(), or writeln() with whatever arguments they 
 were
 given, but only if the user had used a 'enable debugging' 
 command-line
 option (or some such).

 What I first did was this:

 module debugout;

 int debuglevel;

 void set_level(int level) {
 	debuglevel = level;
 }

 auto tdebug(func)(int level, ...) {
 	va_list va;
 	va_start(va, level);
 	if(debuglevel <= level) {
 		return func(va);
 	}
 	va_end(va);
 }

 alias tdebug!(write) wdebug;
 alias tdebug!(writef) wdebugf;
 (... and so on...)

 but that didn't work:

 debugout.d(20): Error: template instance tdebug!(write) 
 tdebug!(write) does not match template declaration tdebug(func)

 I had a short look at 
 http://dlang.org/variadic-function-templates.html
 which would seem to be a somewhat better way of implementing 
 this, but I
 can't figure out how exactly I should go forward, then.

 I do believe that something like the following would do what I 
 want:

 auto wdebug(level, ...) {
 	va_list va;
 	va_start(va, level);
 	writefx(stdout, ???, va);
 	va_end(va);
 }

 except the va_list stuff doesn't seem to be necessary, I don't 
 know what
 to put in place of the "???", and I'd have to write this four 
 times
 rather than being able to template it four times.

 How should I do this instead?


http://dpaste.dzfl.pl/3efd9c1b - try this.
Jul 02 2012
prev sibling next sibling parent reply "nazriel" <nazriel6969 gmail.com> writes:
On Tuesday, 3 July 2012 at 03:15:02 UTC, Wouter Verhelst wrote:

 So, I wanted to create a number of functions that would call 
 write(),
 writef(), writefln(), or writeln() with whatever arguments they 
 were
 given, but only if the user had used a 'enable debugging' 
 command-line
 option (or some such).

 What I first did was this:

 module debugout;

 int debuglevel;

 void set_level(int level) {
 	debuglevel = level;
 }

 auto tdebug(func)(int level, ...) {
 	va_list va;
 	va_start(va, level);
 	if(debuglevel <= level) {
 		return func(va);
 	}
 	va_end(va);
 }

 alias tdebug!(write) wdebug;
 alias tdebug!(writef) wdebugf;
 (... and so on...)

 but that didn't work:

 debugout.d(20): Error: template instance tdebug!(write) 
 tdebug!(write) does not match template declaration tdebug(func)

 I had a short look at 
 http://dlang.org/variadic-function-templates.html
 which would seem to be a somewhat better way of implementing 
 this, but I
 can't figure out how exactly I should go forward, then.

 I do believe that something like the following would do what I 
 want:

 auto wdebug(level, ...) {
 	va_list va;
 	va_start(va, level);
 	writefx(stdout, ???, va);
 	va_end(va);
 }

 except the va_list stuff doesn't seem to be necessary, I don't 
 know what
 to put in place of the "???", and I'd have to write this four 
 times
 rather than being able to template it four times.

 How should I do this instead?


Try this - http://dpaste.dzfl.pl/3efd9c1b
Jul 02 2012
parent Wouter Verhelst <wouter grep.be> writes:
"nazriel" <nazriel6969 gmail.com> writes:

 Try this - http://dpaste.dzfl.pl/3efd9c1b


Yes, that's exactly what I need. Thanks.

Looks like I was making it far too difficult for myself :-)

-- 
The volume of a pizza of thickness a and radius z can be described by
the following formula:

pi zz a
Jul 03 2012
prev sibling parent reply Mike Parker <aldacron gmail.com> writes:
On 7/3/2012 12:12 PM, Wouter Verhelst wrote:

 So, I wanted to create a number of functions that would call write(),
 writef(), writefln(), or writeln() with whatever arguments they were
 given, but only if the user had used a 'enable debugging' command-line
 option (or some such).

 What I first did was this:

 module debugout;

 int debuglevel;



Are you aware of debug conditions?

http://dlang.org/version.html#debug

They can be set on the command line or in code at module level. In the 
former case, it's global. In the latter, only module scope.
Jul 03 2012
parent Wouter Verhelst <wouter grep.be> writes:
Mike Parker <aldacron gmail.com> writes:


 On 7/3/2012 12:12 PM, Wouter Verhelst wrote:

 So, I wanted to create a number of functions that would call write(),
 writef(), writefln(), or writeln() with whatever arguments they were
 given, but only if the user had used a 'enable debugging' command-line
 option (or some such).

 What I first did was this:

 module debugout;

 int debuglevel;



 Are you aware of debug conditions?

 http://dlang.org/version.html#debug

 They can be set on the command line or in code at module level. In the
 former case, it's global. In the latter, only module scope.


Yes, but these are defined at compile time, if I understand things
correctly. That's useful, but not what I'm after; the idea would be that
a user of my application could use a '-v' option on the command line to
get more output.

-- 
The volume of a pizza of thickness a and radius z can be described by
the following formula:

pi zz a
Jul 03 2012