SCAN
Returns a pattern matching the longest string that does not contain any
of the characters in the specified string, range, or buffer. The
pattern matches characters until it reaches the end of the line being
searched or until it finds one of the characters in the string, range,
or buffer used as a parameter. SCAN fails if it finds no characters
other than those present in its argument. SCAN succeeds if it finds at
least one character not specified in the first parameter.
Syntax
pattern := SCAN ({string | range | buffer} [, {FORWARD | REVERSE}])
Parameters
string A string containing the characters that cause
TPU to stop matching characters in the searched
text.
range A range containing the characters that cause
TPU to stop matching characters in the searched
text.
buffer A buffer containing the characters that cause
TPU to stop matching characters in the searched
text.
FORWARD A keyword directing TPU to match characters in
the forward direction.
REVERSE A keyword directing TPU to match characters as
follows: First, match characters in the forward
direction until TPU finds a character that is a
member of the set of characters in the specified
buffer, range, or string. Next, return to the
first character that SCAN matched and start
matching characters in the reverse direction until
TPU finds a character in the specified buffer,
range, or string. You can specify REVERSE only if
you are using SCAN in the first element of a
pattern being used in a reverse search. In all
other contexts, specifying REVERSE has no effect.
The behavior enabled by REVERSE allows an
alternate form of reverse search. By default, a
reverse search stops as soon as a successful match
occurs, even if there might have been a longer
successful match in the reverse direction. By
specifying REVERSE with SCAN, you direct TPU
not to stop matching in either direction until it
has matched as many characters as possible.
Examples
1. pat1 := SCAN ('abc');
This assignment statement stores in "pat1" a pattern that matches
the longest string of characters that does not contain an a, b, or
c.
2. pat1 := SCAN ('abc', FORWARD);
This statement has exactly the same effect as Example 1.
3. word := SCAN (' ', REVERSE);
This statement defines the variable "word" to mean the longest
consecutive string of characters that does not include a space
character. If you use the following statement:
the_range := SEARCH (word, REVERSE);
when the cursor is on the "n" in Xanadu in the following text:
"In Xanadu did Kublai Khan a stately pleasure dome decree"
then the variable "the_range" contains the word "Xanadu". This is
because when you use SCAN with REVERSE as the first element of a
pattern, and then use that pattern in a reverse search, SCAN
matches as many characters as possible in both the forward and
reverse directions.
If the cursor is on "n" but you define the variable "word" without
the REVERSE keyword, like this:
word := SCAN (' ');
and then do a reverse search, "the_range" contains the characters
"nadu".
Related Topics
ANCHOR ANY ARB MATCH NOTANY SCANL
SEARCH SEARCH_QUIETLY SPAN SPANL UNANCHOR