Compaq AA-PWCBD-TE manual Relational Operators

DEC Text Processing Utility Data Types

3.7 Pattern Data Type

pat1 := "abc" + (arb(2) @ var1) + remain;

SEARCH or SEARCH_QUIETLY also assigns to var1 a range that contains the text de.

If you assign to a variable a partial pattern that matches a position, rather than a character, the partial pattern variable is a range that contains the character or line-end at the point in the file where the partial pattern was matched. For example, in any of the following patterns that contain partial pattern assignments, the variable partial_pattern_variable contains the character or line-end at the point in the file where the partial pattern was matched:

•"" @ partial_pattern_variable

•ANCHOR @ partial_pattern_variable

•UNANCHOR @ partial_pattern_variable

•LINE_BEGIN @ partial_pattern_variable

•BUFFER_BEGIN @ partial_pattern_variable

If you use one of the preceding patterns when the cursor is free (that is, in an area that does not contain text, such as the area after the end of a line), the variable partial_pattern_variable contains the line-end or character nearest to the cursor.

SEARCH or SEARCH_QUIETLY does partial pattern assignment only if the complete pattern matches. If the complete pattern matches, it makes assignments only to those variables paired with pattern elements that are used in the complete match. If a partial pattern assignment variable appears more than once in a pattern in places where it is legal for a partial pattern assignment to occur, the last occurrence in the pattern determines what range SEARCH assigns to the variable. For example, with the search text abcdefg and the following pattern, SEARCH or SEARCH_QUIETLY returns a range that contains the text abcde and assigns a range that contains the text d to the variable var1:

pat1 := "a" + ("b" @ var1) + "c" + ("d" @ var1)

+("e" ("x" @ var1));

3.7.3.5Relational Operators

You can use the two relational operators, equal ( = ) and not equal (<>), to compare patterns. Two patterns are equal if they are the same pattern, as pat1 and pat2 are in the following example:

pat1 := notany("abc", 2) + span("123"); pat2 := pat1;

Two patterns are also equal if they have the same internal representation. Patterns have the same internal representation only if they are built in exactly the same way. The order of the characters in the arguments to ANY, NOTANY, SCAN, SCANL, SPAN, and SPANL does not matter when you are comparing patterns returned by any of these built-ins. Other than this, almost any difference in the building of two patterns makes those patterns unequal. For example, suppose you defined the variable this_pat as follows:

this_pat := ANY ("abc");

DEC Text Processing Utility Data Types 3–15