Move match into core library.

lib/match.janet

@@ -1,49 +0,0 @@
-
-# Sentinel value bad matches
-(def- sentinel ~',(gensym))
-
-(defn- match-1
-  [pattern expr onmatch seen]
-  (cond
-    (and (symbol? pattern) (not (keyword? pattern)))
-    (if (get seen pattern)
-      ~(if (= ,pattern ,expr) ,onmatch ,sentinel)
-      (do
-        (put seen pattern true)
-        ~(if (= nil (def ,pattern ,expr)) ,sentinel ,onmatch)))
-    (indexed? pattern) 
-    (do
-      (def len (length pattern))
-      (def $arr (gensym))
-      (defn aux [i]
-        (if (= i len)
-          onmatch
-          (match-1 pattern.i ~(get ,$arr ,i) (aux (+ i 1)) seen)))
-      ~(do (def ,$arr ,expr) ,(aux 0)))
-    (dictionary? pattern)
-    (do
-      (def $dict (gensym))
-      (defn aux [key]
-        (if (= key nil)
-          onmatch
-          (match-1 (get pattern key) ~(get ,$dict ,key) (aux (next pattern key)) seen)))
-      ~(do (def ,$dict ,expr) ,(aux (next pattern nil))))
-    :else ~(if (= ,pattern ,expr) ,onmatch ,sentinel)))
-
-(defmacro match
-  "Pattern matching."
-  [x & cases]
-  (if (not (atomic? x))
-    (do (def $x (gensym)) ~(do (def ,$x ,x) ,(match $x ;cases)))
-    (do
-      (def len (length cases))
-      (def len-1 (dec len))
-      (defn aux [i]
-        (cond
-          (= i len-1) (get cases i)
-          (< i len-1) (do
-                        (def $res (gensym))
-                        ~(if (= ,sentinel (def ,$res ,(match-1 cases.i x (get cases (inc i)) @{})))
-                           ,(aux (+ 2 i))
-                           ,$res))))
-      (aux 0))))