PRXPOSN Function

Returns the value for a capture buffer

Category: Character String Matching

Restriction: Use with the PRXPARSE function

Syntax

PRXPOSN ( regular-expression -id , capture-buffer , source )

Arguments

regular-expression-id

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

capture-buffer

is a numeric value that identifies the capture buffer for which to retrieve a value:
- If the value of capture-buffer is zero, PRXPOSN returns the entire match.
- If the value of capture-buffer is between 1 and the number of open parentheses in the regular expression, then PRXPOSN returns the value for that capture buffer.
- If the value of capture-buffer is greater than the number of open parentheses, then PRXPOSN returns a missing value.

source

specifies the text from which to extract capture buffers.

Details

The PRXPOSN function uses the results of PRXMATCH , PRXSUBSTR, PRXCHANGE, or PRXNEXT to return a capture buffer. A match must be found by one of these functions for PRXPOSN to return meaningful information.

A capture buffer is part of a match, enclosed in parentheses, that is specified in a regular expression. This function simplifies using capture buffers by returning the text for the capture buffer directly, and by not requiring a call to SUBSTR as in the case of CALL PRXPOSN.

For more informaiton about pattern matching, see 'Pattern Matching Using SAS Regular Expressions (RX) and Perl Regular Expressions (PRX)' on page 260.

Comparisons

The PRXPOSN function is similar to the CALL PRXPOSN routine, except that it returns the capture buffer itself rather than the position and length of the capture buffer.

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 'Functions and CALL Routines by Category' on page 270.

Examples

Example 1: Extracting First and Last Names

The following example uses PRXPOSN to extract first and last names from a data set.

 data ReversedNames;     input name & .;     datalines;  Jones, Fred  Kavich, Kate  Turley, Ron  Dulix, Yolanda  ;  data FirstLastNames;     length first last $ 16;     keep first last;     retain re;     if _N_ = 1 then        re = prxparse('/(\w+), (\w+)/');     set ReversedNames;     if prxmatch(re, name) then        do;           last = prxposn(re, 1, name);           first = prxposn(re, 2, name);        end;  run;  options pageno=1 nodate ls=80 ps=64;  proc print data = FirstLastNames;  run;

Output 4.39: Output from PRXPOSN-First and Last Names

 The SAS System            1  Obs     first       last   1      Fred       Jones   2      Kate       Kavich   3      Ron        Turley   4      Yolanda    Dulix

Example 2: Extracting Names When Some Names Are Invalid

The following example creates a data set that contains a list of names. Observations that have only a first name or only a last name are invalid. PRXPOSN extracts the valid names from the data set, and writes the names to the data set NEW.

 data old;     input name .;     datalines;  Judith S Reaveley  Ralph F. Morgan  Jess Ennis  Carol Echols  Kelly Hansen Huff  Judith  Nick  Jones  ;  data new;     length first middle last $ 40;     keep first middle last;     re = prxparse('/(\S+)\s+([^\s]+\s+)?(\S+)/o');     set old;     if prxmatch(re, name) then        do;           first = prxposn(re, 1, name);           middle = prxposn(re, 2, name);           last = prxposn(re, 3, name);           output;        end;  run;  options pageno=1 nodate ls=80 ps=64;  proc print data = new;  run;

Output 4.40: Output of Valid Names

 The SAS System                1  Obs  first     middle    last   1   Judith    S         Reaveley   2   Ralph     F.        Morgan   3   Jess                Ennis   4   Carol               Echols   5   Kelly     Hansen    Huff