On 12 Nov 2008, at 11:11, Andrew Birkett wrote:
Hi,
Is a formal proof that the Haskell language is referentially transparent? Many people state "haskell is RT" without backing up that claim. I know that, in practice, I can't write any counter- examples but that's a bit handy-wavy. Is there a formal proof that, for all possible haskell programs, we can replace coreferent expressions without changing the meaning of a program?
(I was writing a blog post about the origins of the phrase 'referentially transparent' and it made me think about this)
I think the informal proof goes along the lines of "because that's what the spec says" -- Haskell's operational semantics are not specified in the report, only IIRC a wooly description of having some sort of non-strict beta-reduction behavior. Bob