CODEWITHSUNDEEP
lispcommon-lisp
moe
moe

Reputation: 49

Compare strings in lisp

I'm trying to check if a string exists in another string using lisp. I tried the following:

    (string<=  "walk" "wall")

and it gives: "3"

What i need to do is to check if the whole string in the left hand side (^walk) is in the right hand side (not the substrings), so for the previous example it should give false and with :

    (string<=  "walk" "walk on")

it should be true or "4".

Any help please.

Thanks in advance

Upvotes: 0

Views: 1120

Answers (2)

Vatine
Vatine

Reputation: 21258

Based on your comments, you're looking for a string-prefix. The Common Lisp idiom for that is (string= pattern haystack :end2 (length pattern)).

Upvotes: 3

jarmond
jarmond

Reputation: 1382

In SBCL Common Lisp

(search "walk" "wall") -> NIL
(search "walk" "walk on") -> 0

Thus 0 indicates the index of the first match. If you wanted the end of the first match you could do

(let ((pat "walk"))
  (+ (length pat) (search pat "walk on"))) -> 4

Upvotes: 7

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