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(emacs-lisp-intro.info)fwd-sentence re-search


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The regular expression search
-----------------------------

   The `re-search-forward' function searches for the end of the
sentence, that is, for the pattern defined by the `sentence-end'
regular expression.  If the pattern is found--if the end of the
sentence is found--then the `re-search-forward' function does two
things:

  1. The `re-search-forward' function carries out a side effect, which
     is to move point to the end of the occurrence found.

  2. The `re-search-forward' function returns a value of true.  This is
     the value received by the `if', and means that the search was
     successful.

The side effect, the movement of point, is completed before the `if'
function is handed the value returned by the successful conclusion of
the search.

   When the `if' function receives the value of true from a successful
call to `re-search-forward', the `if' evaluates the then-part, which is
the expression `(skip-chars-backward " \t\n")'.  This expression moves
backwards over any blank spaces, tabs or carriage returns until a
printed character is found and then leaves point after the character.
Since point has already been moved to the end of the pattern that marks
the end of the sentence, this action leaves point right after the
closing printed character of the sentence, which is usually a period.

   On the other hand, if the `re-search-forward' function fails to find
a pattern marking the end of the sentence, the function returns false.
The false then causes the `if' to evaluate its third argument, which is
`(goto-char par-end)':  it moves point to the end of the paragraph.

   Regular expression searches are exceptionally useful and the pattern
illustrated by `re-search-forward', in which the search is the test of
an `if' expression, is handy.  You will see or write code incorporating
this pattern often.


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