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Diffstat (limited to 'ipl/procs/scanset.icn')
| -rw-r--r-- | ipl/procs/scanset.icn | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/ipl/procs/scanset.icn b/ipl/procs/scanset.icn new file mode 100644 index 0000000..14b6187 --- /dev/null +++ b/ipl/procs/scanset.icn @@ -0,0 +1,68 @@ +############################################################################ +# +# File: scanset.icn +# +# Subject: Procedures setup for string scanning procedures +# +# Author: Robert J. Alexander +# +# Date: June 4, 1993 +# +############################################################################ +# +# This file is in the public domain. +# +############################################################################ +# +# Procedure to set up for user-written string-scanning procedures that +# are in the spirit of Icon's built-ins. +# +# The values passed are the s, i1, i2 parameters which are the last +# three arguments to all Icon scanning functions (such as +# upto(c,s,i1,i2)). scan_setup() supplies any appropriate defaults and +# returns needed values. +# +# The value returned is a "scan_setup_result" record consisting of two +# values: +# +# 1. The substring of s to be scanned (ss). +# 2. The size of the substring of s that precedes the +# substring to be scanned (offset). +# +# scan_setup() fails if i1 or i2 is out of range with respect to s. +# +# The user-written procedure can then match in the string ss to compute +# the position within ss appropriate to the scan (p). The value +# returned (or suspended) to the caller is p + offset (the position +# within the original string, s). +# +# For example, the following function finds two words separated by +# spaces: +# +# procedure two_words(s,i1,i2) +# local x,p +# x := scan_setup(s,i1,i2) | fail # fail if out of range +# x.ss ? suspend { +# tab(upto(&letters)) & +# pos(1) | (move(-1) & tab(any(~&letters))) & +# p := &pos & # remember starting position +# tab(many(&letters)) & +# tab(many(' ')) & +# tab(many(&letters)) & +# p + x.offset # return position in original s +# } +# end +# + +record scan_setup_result( + ss, # substring to be scanned + offset) # length of substring preceding ss + +procedure scan_setup(s,i1,i2) + if /s := &subject then + /i1 := &pos + else + /i1 := 1 + /i2 := 0 + return scan_setup_result(s[i1:i2],match("",s,i1,i2) - 1) +end |