PRXPARSE Function

Compiles a Perl regular expression (PRX) that can be used for pattern matching of a character value.

Category:	Character String Matching
Restriction:	Use with other Perl regular expressions.

Syntax

regular-expression-id=PRXPARSE (perl-regular-expression)

Required Arguments

regular-expression-id

is a numeric pattern identifier that is returned by the PRXPARSE function.

perl-regular-expression

specifies a character value that is a Perl regular expression.

Details

The Basics

The PRXPARSE function returns a pattern identifier number that is used by other Perl functions and CALL routines to match patterns. If an error occurs in parsing the regular expression, SAS returns a missing value.

PRXPARSE uses metacharacters in constructing a Perl regular expression. To view a table of common metacharacters, see Tables of Perl Regular Expression (PRX) Metacharacters.

For more information about pattern matching, see Pattern Matching Using Perl Regular Expressions (PRX) .

Compiling a Perl Regular Expression

If perl-regular-expression is a constant or if it uses the /o option, the Perl regular expression is compiled only once. Successive calls to PRXPARSE will not cause a recompile, but will return the regular-expression-id for the regular expression that was already compiled. This behavior simplifies the code because you do not need to use an initialization block (IF _N_ =1) to initialize Perl regular expressions.

Note: If you have a Perl regular expression that is a constant, or if the regular expression uses the /o option, then calling PRXFREE to free the memory allocation results in the need to recompile the regular expression the next time that it is called by PRXPARSE.The compile-once behavior occurs when you use PRXPARSE in a DATA step. For all other uses, the perl-regular-expression is recompiled for each call to PRXPARSE.

Comparisons

The Perl regular expression (PRX) functions and CALL routines work together to manipulate strings that match patterns. To see a list and short description of these functions and CALL routines, see the Character String Matching category in SAS Functions and CALL Routines by Category.

Example

The following example uses metacharacters and regular characters to construct a Perl regular expression. The example parses addresses and writes formatted results to the SAS log.

data _null_;
   if _N_ = 1 then 
   do;
      retain patternID;
         /* The i option specifies a case insensitive search. */
      pattern = "/ave|avenue|dr|drive|rd|road/i";
      patternID = prxparse(pattern);
   end;
   input street $80.;
   call prxsubstr(patternID, street, position, length);
   if position ^= 0 then
   do;
      match = substr(street, position, length);
      put match:$QUOTE. "found in " street:$QUOTE.;
   end;
   datalines;
153 First Street
6789 64th Ave
4 Moritz Road
7493 Wilkes Place
;

The following lines are written to the SAS log:

   "Ave" found in "6789 64th Ave"
   "Road" found in "4 Moritz Road"