James Kanze wrote:

> nagle@animats.com (John Nagle) wrote in message
> news:<3E1DC072.4060407@animats.com>...
> > C and C++ don't have a way to specify that a function is a "pure
> > function" in that sense.  They should.
>
> That's another question.
>
> Even an omniscient compiler can't detect this.  Functions like acos may
> set the global variable errno, which means that they aren't pure
> functions, in the mathematical sense, even though we want the compiler
> to treat them as such.

Which is an excellent reason for the language to provide a mechanism for the
programmer to explicitly inform the compiler of his intentions.

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