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set in Scheme?
Date: 5 May 88 21:58:28 GMT
From: uhccux!chin at humu.nosc.mil (David Chin)
Does anyone know how to do the equivalent of a Common Lisp "set" in
Scheme. In particular, I would like to be able to pass different
symbols as arguments to a function and then set! or define them inside
the function. Is this style of programming (global side-effects for
function calls) contrary to the Scheme philosophy?
Don't pass the symbol, pass a closure that will assign the variable:
(foo (lambda (new-value) (set! var new-value)))
If you also need to get the value of the variable, or find out its name,
pass an object that can do any operations that need doing:
(foo (lambda (operation)
((set-value!) (lambda (new-value) (set! var new-value)))
Global side effects are not contrary to "scheme philosophy" (although
they are discouraged), but confusing variables with their names is.