On Thu, 15 May 2014 09:40:03 -0400, Manu via Digitalmars-d
<[email protected]> wrote:
On 15 May 2014 22:30, Steven Schveighoffer via Digitalmars-d
<[email protected]> wrote:
On Thu, 15 May 2014 07:52:20 -0400, Manu via Digitalmars-d
<[email protected]> wrote:
On 15 May 2014 10:50, Walter Bright via Digitalmars-d
<[email protected]> wrote:
On 5/14/2014 5:03 PM, Meta wrote:
Allocating memory through new and malloc should always be pure, I
think,
because
failure either returns null in malloc's case,
malloc cannot be pure if, with the same arguments, it returns null
sometimes
and not other times.
Even if it doesn't fail, malloc called with identical arguments still
returns a different result every time.
You can't factor malloc outside a loop and cache the result because
it's being called repeatedly with the same argument like you're
supposed to be able to do with any other pure function.
You shouldn't be able to do that with gcalloc either... how can
gcalloc be
pure?
That only applies to strong-pure functions. malloc would be weak-pure,
since
it returns a mutable pointer.
Why should returning a mutable pointer imply weak purity?
Because if it were strong-pure, the compiler could optimize two sequential
calls as returning the same exact thing. Imagine if a constructor to a
mutable object always returned the same object because the constructor's
parameters were immutable. It would be useless.
-Steve
