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Hi Matthias, ... I will play with your example (it is better than all the words I spent with my looong description: Ok, fine! Let me define my function in a inner scope: > (let ((othervar 2) (f (mm (+ 1 othervar)))) > (f 1) it should print 4 but it gives the undefined identifier error. If I define "othervar" globally (top env) it works (of course!). > (define othervar 2) > (let ((f (mm (+ 1 othervar)))) (f 1) it prints 4. If you ask me why I need to call "mm" with an _expression_, instead of a value... like: (mm (+ 1 othervar)) The answer is: my macro "replace" is a constructor of a function... I would like that this function could reference external variables (not passed by parameters): if the reference extern variable is defined (in the current scope) its value is used, otherwise the function must give the "undefined identifier error". The function I refer to is a "chemical reaction function": it applies to chemical molecules (the macro parameters) but it can use reference to external variables to fire or not the reaction. Example (replace x y by x if (> x top)) -> #<procedure> says: replace any pair of two molecules (x and y) with only one of them if the value of the first is not greater than "top". Cheers, Maurizio. -- |
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