12 Aug
2009
12 Aug
'09
11:11 p.m.
Derek Elkins wrote:
The compiler is supposed to be able to reorder non-strict evaluation to do optimisations, but that can't be done if effects could happen.
There's nothing special about non-strict evaluation that makes the antecedent true. Replacing "non-strict" with "strict" gives just as much of a valid statement. It is purity that allows (some) reordering of evaluation.
Here are two effectful statements that can safely be reordered. print "foo" x := 5 here are two more y := 2 z := 3 (provided y and z don't alias) Purity allows some reordering of evaluation, so does knowing that two effectful computations won't interfere. Ben.