[newLISP] reverse-find

I've always thought learning Lisp would be a good thing to do. The purists may argue that newLISP is not the best place to start. Oh well, too bad.

Below is my first (ever) lambda expression, a port of the VBScript RevInstr() function.

(set 'reverse-find (lambda (findThis inThis) (- (length inThis) (find (reverse findThis) (reverse inThis)) (length findThis))))

I must say I'm impressed with newLISP. Note that the minus (-) function above can receive more than one argument. A lot of the functions are like that.

Using the reverse-find is very like the (find) function, as below

(set 'toFind "dog") (set 'sentence "My first dog's fleas are on my second dog's blanket") (println (slice sentence (reverse-find toFind sentence) (length toFind))) ; "dog" (println (slice sentence (reverse-find toFind sentence))) ; "dog's blanket" (println (slice sentence (find toFind sentence))) ; "dog's fleas are on my second dog's blanket"

One thing that differentiates my lambda expression from the in-built find, is in the manner in which an error is flagged.

(catch (find "a" "b") 'result) (println result) ; nil (catch (reverse-find "a" "b") 'result) (println result) ; "ERR: value expected : (find (reverse findThis) (reverse inThis))\r\ncalled from user defined function reverse-find"

I'm not sure at this point why the difference and what to do about it. In my use of (find) I check for a result equal to nil, but with (reverse-find) I have to check to see if the result is a string. For example,

(catch (find "a" "b") 'result) (when (nil? result) (println "not found")) (catch (reverse-find "a" "b") 'result) (when (string? result) (println "not found"))

Doubtless, someone in the newLISP Fan Club will set me straight soon.

© Copyright Bruce M. Axtens, 2009