Imagine a simple example, where we want to turn the string "0-5" into "012345".
This works:
>> parse "0-5" [
set a char!
"-"
set b char!
(
while [a <= b] [
prin a
a: a + 1
]
)
]
The result is:
012345
true
But what if I wanted something more general, that could turn "10-12" into "101112", or beyond? This doesn't work:
>> parse "0-5" [
set a [some char!]
"-"
set b [some char!]
(
a-int: to integer! a
b-int: to integer! b
while [a-int <= b-int] [
prin to string! a-int
a-int: a-int + 1
]
)
]
The reason it doesn't work is because instead of set a [some char!] capturing a string of characters, it errors:
>> parse "10" [set a [some char!] (print a)]
** Script error: PARSE - invalid rule or usage of rule: char
** Where: parse
** Near: parse "10" [set a [some char] (print a)]
As a bonus question, why does that fail and using skip returns the first digit only?
>> parse "10" [set a [some skip] (print a)]
1
== true
...when some skip and some char! match equivalently on strings, since the only thing in a string to skip is a character...?
In Parse dialect, SET captures only the first element of the input matched by the sub-rule, while COPY captures all of it. So, you need to use COPY when you want to extract more than one character from a any-string! series.