About this task
There is a special case in which absolute and relative
positional patterns do not work identically. We have shown how parsing
with a template containing a string pattern skips over the data in
the source string that matches the pattern (see
Templates Containing String Patterns). But a template containing the sequence:
- string pattern
- variable name
- relative positional pattern
does
not skip over the matching data. A
relative positional pattern moves relative to the first character
matching a string pattern. As a result, assignment includes the data
in the source string that matches the string pattern.
/* Template containing string pattern, then variable name, then */
/* relative positional pattern does not skip over any data. */
string='REstructured eXtended eXecutor'
parse var string var1 3 junk 'X' var2 +1 junk 'X' var3 +1 junk
say var1||var2||var3 /* Concatenates variables; displays: "REXX" */
Here is how this template works:
│var1 3│ │junk 'X'│ │var2 +1│ │junk 'X'│ │var3 +1 │ │ junk │
└───┬───┘ └───┬────┘ └───┬───┘ └────┬────┘ └───┬────┘ └──┬───┘
│ │ │ │ │ │
Put Starting Starting Starting Starting Starting
characters at 3, put with first with char─ with with char─
1 through characters 'X' put 1 acter after second 'X' acter
2 in var1. up to (not (+1) first 'X' put 1 (+1) after sec─
(Stopping including) character put up to character ond 'X'
point is first 'X' in var2. second 'X' in var3. put rest
3.) in junk. in junk. in junk.
var1='RE' junk= var2='X' junk= var3='X' junk=
'structured 'tended e' 'ecutor'
e'