[gambit-list] equal greater symbol

Marc Feeley feeley at iro.umontreal.ca
Sun Oct 8 20:16:49 EDT 2006


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On 8-Oct-06, at 6:35 PM, Aycan iRiCAN wrote:

> Hi,
>
> What is the meaning of '=> symbol used in cond forms?
>
> Best Regards,

In Scheme the form

(cond (X => F)
       ...)

is equivalent to

(let ((x X))
   (if x
       (F x)
       (cond ...)))

This is useful when the result of the test (the expression X) is  
needed in the clause selected.  This is frequently used in code like

(cond ((assoc X Y) => cdr)
       ...)

Marc


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