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/* Alternative to period as placeholder */
stars='Arcturus Betelgeuse Sirius Rigil'
parse var stars drop junk brightest rest /* brightest='Sirius' */
A placeholder saves the overhead of unneeded variables.
Templates Containing String Patterns
A string pattern matches characters in the source string to indicate where to split it. A string pattern can be
a:
Literal string pattern
One or more characters within quotation marks.
Variable string pattern
A variable within parentheses with no plus (+) or minus (-) or equal sign (=) before the left
parenthesis. (See page 209 for details.)
Here are two templates: a simple template and a template containing a literal string pattern:
var1 var2 /* simple template */
var1 ', ' var2 /* template with literal string pattern */
The literal string pattern is: ', '. This template:
v Puts characters from the start of the source string up to (but not including) the first character of the
match (the comma) into var1
v Puts characters starting with the character after the last character of the match (the character after the
blank that follows the comma) and ending with the end of the string into var2.
A template with a string pattern can omit some of the data in a source string when assigning data into
variables. The next two examples contrast simple templates with templates containing literal string
patterns.
/* Simple template */
name='Smith, John'
parse var name ln fn /* Assigns: ln='Smith,' */
/* fn='John' */
Notice that the comma remains (the variable ln contains 'Smith,'). In the next example the template is ln
','fn. This removes the comma.
/* Template with literal string pattern */
name='Smith, John'
parse var name ln ', ' fn /* Assigns: ln='Smith' */
/* fn='John' */
First, the language processor scans the source string for ', '. It splits the source string at that point. The
variable ln receives data starting with the first character of the source string and ending with the last
character before the match. The variable fn receives data starting with the first character after the match
and ending with the end of string.
A template with a string pattern omits data in the source string that matches the pattern. (There is a
special case (on page 212) in which a template with a string pattern does not omit matching data in the
source string.) We used the pattern ', ' (with a blank) instead of ',' (no blank) because, without the
blank in the pattern, the variable fn receives ' John' (including a blank).
If the source string does not contain a match for a string pattern, then any variables preceding the
unmatched string pattern get all the data in question. Any variables after that pattern receive the null
string.
A null string is never found. It always matches the end of the source string.
Parsing
Chapter 15. Parsing 205