NEWBIE-ish: data as code

[bugmagnet]

It's been a few years since I last did anything with NewLISP. I ought to know the answer to this ...



Can I use data as code? Can I have the name of a function in a string variable and execute the contents of that variable as if it were the name of a function? For example:

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(set 'f "even?")
(f 2.5)


As it stands, that'll give "e" because NewLISP will be thinking I want the 3rd character in the 'f variable. How do I get "even?" to execute against 2.5 (or am I hoping for too much)?



Kind regards,

Bugmagnet

[bugmagnet]

Hmm ... (reading the friendly manual) ... eval-string would seem to be best approach, yes?

[cormullion]

Yes, code is data is code, true, but code consists of strings, symbols, and numbers. So you'll need to move between the different elements of code, using functions such as as eval-string and sym:

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(set 'f "even?")
(apply (sym f) '(2))
;-> true
(map (sym f) '(2 3 4 5))
;-> (true nil true nil)
(map (eval-string "even?") '(2 3 4 5))
;-> (true nil true nil)
(eval-string "(even? 3)")
;-> nil
(eval (read-expr "(even? 4)"))
;-> true