JInterpolate does the interpolation of replacement strings for JRegex.
A summary of the default behavior is as follows. The replacement
metacharacter is '$', which marks the beginning of a replacement token.
'Unclean' replacement patterns are patterns which contain a
metacharacter not immediately followed either by a second metacharacter
or by an optional sign ('-' or '+') preceding one or more decimal
digits. All other patterns are 'clean'. Clean patterns will be
replaced by their corresponding match value, while unclean patterns are
left intact except their '$' is removed; to insert a literal '$'
preface it with a backslash.
In other words, the only clean replacement tokens are those of the form
'$[+-]?[0-9]+' and '${...}', and a replacement pattern is clean unless
it contains at least one unclean replacement token.
The $ pattern behavior is as follows. A $ followed by a positive
number N is replaced by the (N+1)st element of matchList, counting from
the beginning of the list. A $ followed by a negative number -N is
replaced by the Nth element of matchList, *counting from the end of the
list*. If the number refers to an element which does not exist in
matchList, the replacement string is "". Replacement is done in one
pass, so matches which contain '$N' are not subject to further
replacement. Maniacs who want a convenient way to, say, iterate until
a fixed point is reached should write their own loop.
${x} is replaced by the subexpression named "x".
The above rules are easier to understand in the normal case where
matchList was generated by a previous match. Then $0 is the entire
match, while $1 is the first subexpression, $2 the second, and so forth
up to $9, numbering subexpressions by counting left parentheses from
left to right. Similarly, $-1 is the last subexpression, $-2 is the
second to the last, and so on. If the pattern actually only contained
four subexpressions, then $5 through $9 and $-6 through $-10 would be
replaced by "", while both $0 and $-5 would be replaced by the overall
match. Similarly, both $1 and $-4 would be replaced by the first
parenthesized subexpression, $2 and $-3) by the second, $3 and $-2 by
the third, and finally $4 and $-1 by the fourth.
Protected Member Functions inherited from JSubstitute