• asd (12/12) Jul 23 2009 I'm trying to write basic compile-time function:
• Daniel Keep (3/19) Jul 23 2009 That's because n isn't a compile-time constant. You can't instantiate a
• BCS (3/24) Jul 23 2009 that includes "runtime variables" used in CTFE (this is because CTFE fun...
• asd (2/11) Jul 24 2009 In this case value of n is possible to know at compile time - it depends...
• Ary Borenszweig (3/16) Jul 24 2009 So write:

asd <no spam.com> writes:

I'm trying to write basic compile-time function:

string usedForMixin()
{
 int n=0; 
 /* do stuff */
 return "int x = " ~ std.metastrings.ToString!(n) ~ ";";
}

However I'm getting:
/usr/local/bin/../src/phobos/std/metastrings.d(104): Error: expression
cast(long)n is not a valid template value argument

If I change int to long:
/usr/local/bin/../src/phobos/std/metastrings.d(87): Error: expression n < 0L is
not constant or does not evaluate to a bool

(D2, OS X)

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

asd wrote:
 I'm trying to write basic compile-time function:
 
 string usedForMixin()
 {
  int n=0; 
  /* do stuff */
  return "int x = " ~ std.metastrings.ToString!(n) ~ ";";
 }
 
 However I'm getting:
 /usr/local/bin/../src/phobos/std/metastrings.d(104): Error: expression
cast(long)n is not a valid template value argument
 
 If I change int to long:
 /usr/local/bin/../src/phobos/std/metastrings.d(87): Error: expression n < 0L
is not constant or does not evaluate to a bool
 
 (D2, OS X)

That's because n isn't a compile-time constant.  You can't instantiate a
template with runtime variables.

BCS <ao pathlink.com> writes:

Reply to Daniel,

 asd wrote:
 
 I'm trying to write basic compile-time function:
 
 string usedForMixin()
 {
 int n=0;
 /* do stuff */
 return "int x = " ~ std.metastrings.ToString!(n) ~ ";";
 }
 However I'm getting:
 /usr/local/bin/../src/phobos/std/metastrings.d(104): Error:
 expression cast(long)n is not a valid template value argument
 If I change int to long:
 /usr/local/bin/../src/phobos/std/metastrings.d(87): Error: expression
 n < 0L is not constant or does not evaluate to a bool
 (D2, OS X)
 

 That's because n isn't a compile-time constant.  You can't instantiate
 a template with runtime variables.
 

that includes "runtime variables" used in CTFE (this is because CTFE functions 
are also normal runtime functions).

asd <x x.com> writes:

 n < 0L is not constant or does not evaluate to a bool
 (D2, OS X)
 

 That's because n isn't a compile-time constant.  You can't instantiate
 a template with runtime variables.
 

 
 that includes "runtime variables" used in CTFE (this is because CTFE functions 
 are also normal runtime functions).

In this case value of n is possible to know at compile time - it depends only
on compile-time input.

I'm not going to use this function at run time. Too bad I can't declare that :(

Ary Borenszweig <ary esperanto.org.ar> writes:

asd wrote:
 n < 0L is not constant or does not evaluate to a bool
 (D2, OS X)

 That's because n isn't a compile-time constant.  You can't instantiate
 a template with runtime variables.

 that includes "runtime variables" used in CTFE (this is because CTFE functions 
 are also normal runtime functions).

 
 In this case value of n is possible to know at compile time - it depends only
on compile-time input.
 
 I'm not going to use this function at run time. Too bad I can't declare that :(
 

So write:

const int n = 0;