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digitalmars.D.learn - Compile-Time Functions - Allocating Memory?

reply Era Scarecrow <rtcvb32 yahoo.com> writes:
 I'm trying to compose as a test, where i fill a precompiled list of numbers in
an array. What step am i missing to make this part work? (I i'm using gdc). it
keeps complaining of a non-constant expression. Is there any way to make this
work?

bool []primes = tp(1000);

bool [] tp( int max )
{
	bool[] tmp = new bool[](max);

	for ( int cnt = 2; cnt < max; cnt++ )
		tmp[cnt] = isprime( cnt );

	return tmp;
}

bool isprime( int x )
{
	for ( int cnt = 2; cnt < x; cnt++ )
		if ( x % cnt == 0 )
			return false;

	return true;
}

 Era
Jul 22 2008
next sibling parent Ary Borenszweig <ary esperanto.org.ar> writes:
Era Scarecrow a écrit :

  I'm trying to compose as a test, where i fill a precompiled list of numbers
in an array. What step am i missing to make this part work? (I i'm using gdc).
it keeps complaining of a non-constant expression. Is there any way to make
this work?
 
 bool []primes = tp(1000);
 
 bool [] tp( int max )
 {
 	bool[] tmp = new bool[](max);
 
 	for ( int cnt = 2; cnt < max; cnt++ )
 		tmp[cnt] = isprime( cnt );
 
 	return tmp;
 }
 
 bool isprime( int x )
 {
 	for ( int cnt = 2; cnt < x; cnt++ )
 		if ( x % cnt == 0 )
 			return false;
 
 	return true;
 }
 
  Era



lol,

Some days ago I was writing the same thing to make a video showing 
Descent hovering over that constant and the primes would appear.

It seems this can't be interpreted:

new bool[](max);

You can't create anything on the heap when doing CTFE (afaik). I did it 
by using a dynamic array:

bool[] tmp;
tmp ~= false;
tmp ~= false;
for ( int cnt = 2; cnt < max; cnt++ )
   tmp ~= isprime( cnt );

And since CTFE seems to not have garbage collection, you might want to 
do "cnt * cnt <= x" instead of "cnt < x" ;-)
Jul 22 2008
prev sibling parent "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Era Scarecrow" <rtcvb32 yahoo.com> wrote in message 
news:g664l0$2bia$1 digitalmars.com...

 I'm trying to compose as a test, where i fill a precompiled list of 
 numbers in an array. What step am i missing to make this part work? (I i'm 
 using gdc). it keeps complaining of a non-constant expression. Is there 
 any way to make this work?

 bool []primes = tp(1000);



Completely off-topic, but a stylistic point.  Putting the brackets next to 
the name is a bit misleading in D, since unlike in C, type decorators do not 
attach to the variables but instead to the base type.  That is,

char * x, y;

in C means that x is a pointer to a char, while y is a char; but in D, 
they're both char*.  For that reason it's recommended that the 
brackets/asterisks attach to the type.

(I still can't quite figure out why you also use "bool [] tp" and "bool[] 
tmp".  Usually people are consistent about these things ;) )
Jul 22 2008