For those browsing the source, I'll give a quick run through of what's going
on.
1. A "pattern matrix" is built using the given variables and pattern rows. A
Pattern row is a pair of matches and a result.
Example:
match.core=> (build-matrix [x y]
[1 0] 0
[0 1] 1)
#match.core.PatternMatrix[[#match.core.PatternRow[[<LiteralPattern: 1>
<LiteralPattern: 0>],
0, nil] ;; results in 0
#match.core.PatternRow[[<LiteralPattern: 0> <LiteralPattern: 1>],
1, nil]], ;; results in 0
[x y]] ;; the variables to match
2. The pattern matrix is "compiled" into a decision tree, a DAG. Switch
nodes can take multiple routes down the tree, depending on which ":case"
matches the ":occurance".
Example:
match.core=> (-> (build-matrix [x y]
[1 0] 0
[0 1] 1)
compile)
#match.core.SwitchNode{:occurrence x,
:cases ([<LiteralPattern: 0>
#match.core.SwitchNode{:occurrence y,
:cases ([<LiteralPattern: 1>
#match.core.LeafNode{:value 1, :bindings nil}]),
:default #match.core.FailNode{}}]
[<LiteralPattern: 1>
#match.core.SwitchNode{:occurrence y,
:cases ([<LiteralPattern: 0>
#match.core.LeafNode{:value 0, :bindings nil}]),
:default #match.core.FailNode{}}]),
:default #match.core.FailNode{}}
3. The DAG is then converted to the equivalent Clojure code.
match.core=> (-> (build-matrix [x y]
[1 0] 0
[0 1] 1)
compile
to-clj source-pprint)
(cond
(= x 0) (cond
(= y 1) 1
:else (throw (java.lang.Exception. "Found FailNode")))
(= x 1) (cond
(= y 0) 0
:else (throw (java.lang.Exception. "Found FailNode")))
:else (throw (java.lang.Exception. "Found FailNode")))
nil
Ambrose
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