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############################################################################
#
# Name: slshupto.icn
#
# Title: slshupto (upto with backslash escaping)
#
# Author: Richard L. Goerwitz
#
# Version: 1.4
#
############################################################################
#
# Slshupto works just like upto, except that it ignores backslash
# escaped characters. I can't even begin to express how often I've
# run into problems applying Icon's string scanning facilities to
# to input that uses backslash escaping. Normally, I tokenize first,
# and then work with lists. With slshupto() I can now postpone or
# even eliminate the traditional tokenizing step, and let Icon's
# string scanning facilities to more of the work.
#
# If you're confused:
#
# Typically UNIX utilities (and probably others) use backslashes to
# "escape" (i.e. remove the special meaning of) metacharacters. For
# instance, UNIX shells normally accept "*" as a shorthand for "any
# series of zero or more characters. You can make the "*" a literal
# "*," with no special meaning, by prepending a backslash. The rou-
# tine slshupto() understands these backslashing conventions. You
# can use it to find the "*" and other special characters because it
# will ignore "escaped" characters.
#
############################################################################
#
# Links: none
#
# See also: slashbal.icn
#
############################################################################
# for compatibility with the original name
#
procedure slashupto(c, s, i, j)
suspend slshupto(c, s, i, j)
end
#
# slshupto: cset x string x integer x integer -> integers
# (c, s, i, j) -> Is (a generator)
# where Is are the integer positions in s[i:j] before characters
# in c that is not preceded by a backslash escape
#
procedure slshupto(c, s, i, j)
local c2
if /s := &subject
then /i := &pos
else /i := 1
/j := *s + 1
/c := &cset
c2 := '\\' ++ c
s[1:j] ? {
tab(i)
while tab(upto(c2)) do {
if ="\\" then {
move(1) | {
if find("\\", c)
then return &pos - 1
}
next
}
suspend .&pos
move(1)
}
}
end
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