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add support for & _ to match macro

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This commit adds support for using & _ syntax to bind the remaining
values in an array in the match macro.

The commit also adds a few tests for the new syntax in suite0008
This commit is contained in:
Ian Shehadeh 2022-01-19 13:29:34 -05:00
parent 0d31674166
commit db631097b1
2 changed files with 28 additions and 6 deletions
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32
src/boot/boot.janet
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@ -1751,10 +1751,18 @@
(break) (break)
# match data structure template # match data structure template
(or isarr (= t :struct) (= t :table)) (or (= t :struct) (= t :table))
(do
(when isarr (get-length-sym s))
(eachp [i sub-pattern] pattern (eachp [i sub-pattern] pattern
(visit-pattern-1 b2g s i sub-pattern))
isarr
(do
(get-length-sym s)
(eachp [i sub-pattern] pattern
(when (= sub-pattern '&)
# TODO: check that & is followed by something
(put b2g (pattern (inc i)) @[[slice s i]])
(break))
(visit-pattern-1 b2g s i sub-pattern))) (visit-pattern-1 b2g s i sub-pattern)))
# match global unification # match global unification
@ -1774,14 +1782,24 @@
(def isarr (or (= t :array) (and (= t :tuple) (= (tuple/type pattern) :brackets)))) (def isarr (or (= t :array) (and (= t :tuple) (= (tuple/type pattern) :brackets))))
(when isarr (when isarr
(array/push anda (get-length-sym s)) (array/push anda (get-length-sym s))
(array/push anda [<= (length pattern) (get-length-sym s)])) (def pattern-len
(if-let [ rest-idx (find-index (fn [x] (= x '&)) pattern) ]
rest-idx
(length pattern)))
(array/push anda [<= pattern-len (get-length-sym s)]))
(cond (cond
# match data structure template # match data structure template
(or isarr (= t :struct) (= t :table)) (or (= t :struct) (= t :table))
(eachp [i sub-pattern] pattern (eachp [i sub-pattern] pattern
(when (not isarr) (array/push anda [not= nil (get-sym s i)])
(array/push anda [not= nil (get-sym s i)])) (visit-pattern-2 anda gun preds s i sub-pattern))
isarr
(eachp [i sub-pattern] pattern
# stop recursing to sub-patterns if the rest sigil is found
(when (= sub-pattern '&)
(break))
(visit-pattern-2 anda gun preds s i sub-pattern)) (visit-pattern-2 anda gun preds s i sub-pattern))
# match local binding # match local binding

4
test/suite0008.janet
View File

@ -106,6 +106,10 @@
(assert (= nil (match {:a :hi} {:a a :b b} a)) "match 3") (assert (= nil (match {:a :hi} {:a a :b b} a)) "match 3")
(assert (= nil (match [1 2] [a b c] a)) "match 4") (assert (= nil (match [1 2] [a b c] a)) "match 4")
(assert (= 2 (match [1 2] [a b] b)) "match 5") (assert (= 2 (match [1 2] [a b] b)) "match 5")
(assert (= [2 :a :b] (match [1 2 :a :b] [o & rest] rest)) "match 6")
(assert (= [] (match @[:a] @[x & r] r :fallback)) "match 7")
(assert (= :fallback (match @[1] @[x y & r] r :fallback)) "match 8")
(assert (= [1 2 3 4] (match @[1 2 3 4] @[x y z & r] [x y z ;r] :fallback)) "match 9")
# And/or checks # And/or checks