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digitalmars.D - Purity and C functions

reply 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?
Jan 07 2009
parent reply "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
Jan 07 2009
parent 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.
Jan 07 2009