CODEWITHSUNDEEP
searchemacsmatch-data
Thomas Labbé
Thomas Labbé

Reputation: 31

match-data not cleared on failed re-search-forward

I need to make multiples re-search'es in a buffer.

But when the last re-search fails, the match-data still contains the former result.

foo-bar-baz

(progn
  (goto-char (point-min))
  (re-search-forward "^foo-\\(.*\\)-baz" nil t)
  (message "step 1: %S '%s'" (match-data) (match-string-no-properties 1))
  ;; => step 1: (#<marker at 1 in *scratch*> #<marker at 12 in *scratch*> #<marker at 5 in *scratch*> #<marker at 8 in *scratch*>) ’bar’

  (goto-char (point-min))
  (re-search-forward "^baz-\\(.*\\)-foo" nil t)
  (message "step 2: %S '%s'" (match-data) (match-string-no-properties 1))
  ;; => step 2: (#<marker at 1 in *scratch*> #<marker at 12 in *scratch*> #<marker at 5 in *scratch*> #<marker at 8 in *scratch*>) ’bar’
  ;; expected no match-data
  )

I don't get how to use set-match-data and need to know when the last re-search don't matches.

Any advise on a lispy way to do such re-searches ?

Setting NOERROR to t seems to the root cause but clearer than excpecting errors everywhere in my re-searches.

Upvotes: 1

Views: 56

Answers (2)

phils
phils

Reputation: 73344

I think your question is this:

I need to know when the last re-search doesn't match

You do that by testing the return value of the search:

(when (re-search-forward REGEXP nil t)
  ;; the search succeeded (and so match-data has been set
  ;; based on that search).
  )

Upvotes: 0

Thomas Labb&#233;
Thomas Labb&#233;

Reputation: 31

According to @Drew suggestion save-match-data give an all new match-data just as I wanted:

foo-bar-baz

(progn
  (save-match-data
    (goto-char (point-min))
    (re-search-forward "^foo-\\(.*\\)-baz" nil t)
    (message "step 1: %S" (match-string-no-properties 1))) 
;; => step 1 : "bar"

  (save-match-data
    (goto-char (point-min))
    (re-search-forward "^baz-\\(.*\\)-foo" nil t)
    (message "step 2: %S" (match-string-no-properties 1))) 
;; => step 2: no nil
  )

Upvotes: 1

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