Using the fixed position specifier
The fixed position specifier is positioned at a particular operand in the input string.
Sometimes it is necessary to position the pattern matching at a particular operand in the input string. This is handled by the %n fixed position specifier. Examples of the fixed position specifier are:
| Fixed Position Specifier | Value |
|---|---|
| %1 | Matches to the first token |
| %2 | Matches to the second token |
| %–1 | Matches to the last token |
| %–2 | Matches to the second from last token |
The positions can be qualified by following the %n with a token type. Some examples are:
| Fixed Position Specifier | Value |
|---|---|
| %2^ | Matches to the second numeric token |
| %-1^ | Matches to the last numeric token |
| %3T | Matches to the third street type token |
| %2? | Matches to the second set of two or more unknown alphabetic tokens |
You can use the fixed position specifier (%) in only two ways:
- As the first operand of a pattern
- As the first and second operands of a pattern
The following pattern is allowed and matches the second numeric token as operand [1] and the third leading alpha token that follows as operand [2]:
%2^ | %3<
The fixed position specifier treats each token according to its class. The following examples illustrate how to use the fixed position specifier for the input field:
John Doe
123 Martin Luther St
Salt Lake
| Fixed Position Specifier | Description |
|---|---|
| %1 1 | Matches to the first word in the first string: JOHN |
| %1 2 | Matches to the second word in the first string: DOE |
| %2 ? | Matches to the second string of unknown alphabetic words: MARTIN LUTHER |
| %2 1 | Matches to the first word in the second string: MARTIN |
| %-2 –1 | Matches to the last word in the next to the last string: LUTHER |
| %3+ | Matches to the third single alphabetic word: MARTIN |
| %–1 ? | Matches to the last string of unknown alphabetic words: SALT LAKE |
| %–1+ | Matches to the last single alphabetic word: LAKE |
The position specifier does not continue scanning if a pattern fails to match (unlike * and #).
Assuming the input value S is classified as a D for direction, the following pattern matches the 789 S in the string 123 A 456 B 789 S:
%3^ | D
That same pattern does not match 123 A 456 B 789 C 124 S because the third number (789) is not followed by a direction.