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fogus/thread.clj

Forked from richhickey/thread.clj
Created October 15, 2012 13:45
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new thread macros draft
Raw
thread.clj
(defmacro test->
"Takes an expression and a set of test/form pairs. Threads expr (via ->)
through each form for which the corresponding test is true."
[expr
& clauses]
(assert (even? (count clauses)))
(let [g (gensym)
pstep (fn [[test step]] `(if ~test (-> ~g ~step) ~g))]
`(let [~g ~expr
~@(interleave (repeat g) (map pstep (partition 2 clauses)))]
~g)))
(defmacro test->>
"Takes an expression and a set of test/form pairs. Threads expr (via ->>)
through each form for which the corresponding test is true."
[expr & clauses]
(assert (even? (count clauses)))
(let [g (gensym)
pstep (fn [[test step]] `(if ~test (->> ~g ~step) ~g))]
`(let [~g ~expr
~@(interleave (repeat g) (map pstep (partition 2 clauses)))]
~g)))
(defmacro let->
"Binds name to expr, evaluates the first form in the lexical context
of that binding, then binds name to that result, repeating for each
successive form"
[expr name & forms]
`(let [~name ~expr
~@(interleave (repeat name) forms)]
~name))
(defmacro when->
"When expr is logical true, threads it into the first form (via ->),
and when that result is logical true, through the next etc"
[expr & forms]
(let [g (gensym)
pstep (fn [step] `(when ~g (-> ~g ~step)))]
`(let [~g ~expr
~@(interleave (repeat g) (map pstep forms))]
~g)))
(defmacro when->>
"When expr is logical true, threads it into the first form (via ->>),
and when that result is logical true, through the next etc"
[expr & forms]
(let [g (gensym)
pstep (fn [step] `(when ~g (->> ~g ~step)))]
`(let [~g ~expr
~@(interleave (repeat g) (map pstep forms))]
~g)))
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