[Haskell] NYTimes.com: John W. Backus, 82, Fortran Developer, Dies
Douglas Philips
dgou at mac.com
Tue Mar 20 15:37:28 EDT 2007
On 2007 Mar 20, at 3:30 PM, Dan Weston indited:
> I looked up John Backus on wikipedia and followed a link to ALGOL:
> http://en.wikipedia.org/wiki/ALGOL_60
> where the following "undesirable" property of call-by-name is
> mentioned.
>
> "ALGOL 60 allowed for two evaluation strategies for parameter
> passing: the common call-by-value, and call-by-name. Call-by-name
> had certain limitations in contrast to call-by-reference, making it
> an undesirable feature in language design. For example, it is
> impossible in ALGOL 60 to develop a procedure that will swap the
> values of two parameters if the actual parameters that are passed
> in are an integer variable and an array that is indexed by that
> same integer variable. However, call-by-name is still beloved of
> ALGOL implementors for the interesting thunks that are used to
> implement it."
>
> I suppose that call-by-name is still beloved of Haskell
> implementors as well?
Notice that the "problem" with call-by-name is when side-effects are
involved. In a pure-functional-environment those "problems" don't
arise...
--Doug
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