[Haskell] NYTimes.com: John W. Backus, 82, Fortran Developer, Dies
Dan Weston
westondan at imageworks.com
Tue Mar 20 16:00:18 EDT 2007
Douglas Philips wrote:
> 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
It was the phrase "making it an undesirable feature in language design"
that jumped out at me. Here "language" is an implicitly universally
quantified variable, and the phrase beta-reduces to "call-by-name is an
undesirable feature in Haskell design".
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