• dsimcha (2/2) Jan 07 2009 If someone wants to call C code from a pure D function, how can this be ...
• Denis Koroskin (6/9) Jan 07 2009 Purite can't be checked on extern functions. It these cases DMD should r...
• Walter Bright (3/5) Jan 07 2009 If you declare as pure functions that are impure, you'll get undefined

dsimcha <dsimcha yahoo.com> writes:

If someone wants to call C code from a pure D function, how can this be done?
 How does one tell DMD that the C function is, in fact, pure?

"Denis Koroskin" <2korden gmail.com> writes:

On Thu, 08 Jan 2009 06:00:35 +0300, dsimcha <dsimcha yahoo.com> wrote:

 If someone wants to call C code from a pure D function, how can this be  
 done?
  How does one tell DMD that the C function is, in fact, pure?

Purite can't be checked on extern functions. It these cases DMD should rely on
programmer.
For example, you could define strstr as follows:

extern(C) pure invariant(char)* strstr(invariant(char)* str1, invariant(char)*
str2);

This way it is truly pure.

I wonder what results you may get using "extern(C) pure int rand();" though. :p

Walter Bright <newshound1 digitalmars.com> writes:

Denis Koroskin wrote:
 I wonder what results you may get using "extern(C) pure int rand();" 
 though. :p

If you declare as pure functions that are impure, you'll get undefined 
behavior.