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Code Issues 1 Releases Wiki Activity

Add backmatch operator to pegs.

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(backmatch [tag?]) is similar to a back reference in regular expressions
(NOT to backwards capture in a peg). It only matches a pattern if
it exactly matches the text of the last capture. It does not consume
or push any captures to the capture stack.
This commit is contained in:
Calvin Rose
2019-08-24 18:57:01 -04:00
parent 78b5c94cb0
commit 711fe64a51
2 changed files with 53 additions and 2 deletions
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22
test/suite3.janet
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@@ -356,6 +356,28 @@
(check-match janet-longstring "``` `` ```" true)
(check-match janet-longstring "`` ```" false)
# Backmatch
(def backmatcher-1 '(* (capture (any "x") :1) "y" (backmatch :1) -1))
(check-match backmatcher-1 "y" true)
(check-match backmatcher-1 "xyx" true)
(check-match backmatcher-1 "xxxxxxxyxxxxxxx" true)
(check-match backmatcher-1 "xyxx" false)
(check-match backmatcher-1 "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxy" false)
(check-match backmatcher-1 (string (string/repeat "x" 10000) "y") false)
(check-match backmatcher-1 (string (string/repeat "x" 10000) "y" (string/repeat "x" 10000)) true)
(def backmatcher-2 '(* '(any "x") "y" (backmatch) -1))
(check-match backmatcher-2 "y" true)
(check-match backmatcher-2 "xyx" true)
(check-match backmatcher-2 "xxxxxxxyxxxxxxx" true)
(check-match backmatcher-2 "xyxx" false)
(check-match backmatcher-2 "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxy" false)
(check-match backmatcher-2 (string (string/repeat "x" 10000) "y") false)
(check-match backmatcher-2 (string (string/repeat "x" 10000) "y" (string/repeat "x" 10000)) true)
# Optional
(check-match '(* (opt "hi") -1) "" true)