• freeagle <dalibor.free gmail.com> Oct 02 2007
• BCS <ao pathlink.com> Oct 02 2007
• freeagle <dalibor.free gmail.com> Oct 02 2007
• BCS <ao pathlink.com> Oct 02 2007
• Daniel Keep <daniel.keep.lists gmail.com> Oct 02 2007
• freeagle <dalibor.free gmail.com> Oct 03 2007

freeagle <dalibor.free gmail.com> writes:

Hello,

is it possible somehow, to pass as a lazy argument expression with 
argument/s?

something like
foo((int x) x == 0);

where x will be passed as parameter to the exp inside the foo function:

void foo(lazy bool dg)
{
	if(dg(10)) {...}
}


i'd like not to have to use foo(bool delegate(int x) {return x == 0}) if 
possible

I hope i made myself clear, thanks for advices in advance :)

freeagle

BCS <ao pathlink.com> writes:

Reply to freeagle,

 Hello,
 
 is it possible somehow, to pass as a lazy argument expression with
 argument/s?
 
 something like
 foo((int x) x == 0);
 where x will be passed as parameter to the exp inside the foo
 function:
 
 void foo(lazy bool dg)
 {
 if(dg(10)) {...}
 }
 i'd like not to have to use foo(bool delegate(int x) {return x == 0})
 if possible
 
 I hope i made myself clear, thanks for advices in advance :)
 
 freeagle
 


the best you can do would be use the short form of delegates

foo((int x) {return x == 0;})

it's 3 char's longer than what you asked for but.


OTOH could the syntax be changed so that a delegate uses a statement rather 
than a block?

foo(bool delegate(int) a, int b);

foo((int x) return x == 0;, 5)

freeagle <dalibor.free gmail.com> writes:

BCS wrote:
 Reply to freeagle,
 
 Hello,

 is it possible somehow, to pass as a lazy argument expression with
 argument/s?

 something like
 foo((int x) x == 0);
 where x will be passed as parameter to the exp inside the foo
 function:

 void foo(lazy bool dg)
 {
 if(dg(10)) {...}
 }
 i'd like not to have to use foo(bool delegate(int x) {return x == 0})
 if possible

 I hope i made myself clear, thanks for advices in advance :)

 freeagle


 the best you can do would be use the short form of delegates
 
 foo((int x) {return x == 0;})
 
 it's 3 char's longer than what you asked for but.
 
 
 OTOH could the syntax be changed so that a delegate uses a statement 
 rather than a block?
 
 foo(bool delegate(int) a, int b);
 
 foo((int x) return x == 0;, 5)
 
 



hmm, well, if thats the shortest possible form...

i wanted to make a template representing mathematical sets, that would 
be defined something like MSet!(int)(x > 0 && x < 10, x*2)
but with the returns and all, it looks weird:
MSet!(int)((int x) {return x > 0 && x < 10; }, (int x) { return x * 2; })

freeagle

BCS <ao pathlink.com> writes:

Reply to freeagle,

 
 i wanted to make a template representing mathematical sets, that would
 be defined something like MSet!(int)(x > 0 && x < 10, x*2)
 but with the returns and all, it looks weird:
 MSet!(int)((int x) {return x > 0 && x < 10; }, (int x) { return x * 2;
 })
 freeagle
 


there is one other option

void foo(inout int i, lazy bool b)
{
  int j = 0;
  do
    i = j++;
  while(dg());
}

use like this

int k;
foo(k, k <= 5);

I would consider that an "ugly hack".

Daniel Keep <daniel.keep.lists gmail.com> writes:

freeagle wrote:
 hmm, well, if thats the shortest possible form...
 
 i wanted to make a template representing mathematical sets, that would
 be defined something like MSet!(int)(x > 0 && x < 10, x*2)
 but with the returns and all, it looks weird:
 MSet!(int)((int x) {return x > 0 && x < 10; }, (int x) { return x * 2; })
 
 freeagle


You could always use something like this:

MSet!(int, "$ > 0 && $ < 10", "$ * 2");

Then use CTFE to replace the '$' with whatever symbol it uses
internally, and then string mixin the result.

Not *quite* as clean as you wanted, but at least there aren't any nasty
delegate literals!

	-- Daniel

freeagle <dalibor.free gmail.com> writes:

Daniel Keep Wrote:

 
 
 freeagle wrote:
 hmm, well, if thats the shortest possible form...
 
 i wanted to make a template representing mathematical sets, that would
 be defined something like MSet!(int)(x > 0 && x < 10, x*2)
 but with the returns and all, it looks weird:
 MSet!(int)((int x) {return x > 0 && x < 10; }, (int x) { return x * 2; })
 
 freeagle


 You could always use something like this:
 
 MSet!(int, "$ > 0 && $ < 10", "$ * 2");
 
 Then use CTFE to replace the '$' with whatever symbol it uses
 internally, and then string mixin the result.
 
 Not *quite* as clean as you wanted, but at least there aren't any nasty
 delegate literals!
 
 	-- Daniel



thanks Daniel