luciano/xforms
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Make x/for to unroll some reductions

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When an expression in collection position in `x/for` is a collection literal with less than 4 items (or tagged with `^:unroll`) then the collection is not allocated and the reduction over it is unrolled.
This commit is contained in:
Christophe Grand 2017-09-19 17:26:11 +02:00
parent 23feac44dc
commit 8f04ad0748
3 changed files with 70 additions and 40 deletions
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12
README.md
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@ -21,7 +21,7 @@ Transducing contexts: `transjuxt` (for performing several transductions in a sin
Add this dependency to your project:
```clj
[net.cgrand/xforms "0.9.4"]
[net.cgrand /xforms "0.9.5"]
```
```clj
@ -209,6 +209,16 @@ Evaluation count : 24 in 6 samples of 4 calls.
## Changelog
### 0.9.5
* Short (up to 4) literal collections (or literal collections with `:unroll` metadata) in collection positions in `x/for` are unrolled.
This means that the collection is not allocated.
If it's a collection of pairs (e.g. maps), pairs themselves won't be allocated.
### 0.9.4
* Add `x/into-by-key` short hand
### 0.7.2
* Fix transients perf issue in Clojurescript

2
project.clj
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@ -1,4 +1,4 @@
(defproject net.cgrand/xforms "0.9.4"
(defproject net.cgrand/xforms "0.9.5"
:description "Extra transducers for Clojure"
:url "https://github.com/cgrand/xforms"
:license {:name "Eclipse Public License"

22
src/net/cgrand/xforms.cljc
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@ -15,6 +15,16 @@
(defn- no-user-meta? [x]
(= {} (dissoc (or (meta x) {}) :file :line :column :end-line :end-column)))
(defmacro unreduced->
"Thread first while threaded value is not reduced.
Doesn't unreduce the final value."
([x] x)
([x expr & exprs]
`(let [x# ~x]
(if (reduced? x#)
x#
(unreduced-> (-> x# ~expr) ~@exprs)))))
(defmacro for
"Like clojure.core/for with the first expression being replaced by % (or _). Returns a transducer.
When the first expression is not % (or _) returns an eduction."
@ -33,12 +43,22 @@
:let `(let ~expr ~body)
:when `(if ~expr ~body ~acc)
:while `(if ~expr ~body (reduced ~acc))
(if (and (coll? expr) (not (seq? expr))
(or (<= (core/count expr) 4) (:unroll (meta expr))))
(let [body-rf (gensym 'body-rf)]
(if (and (destructuring-pair? binding) (every? vector? expr))
`(let [~body-rf (fn [~acc ~@binding] ~body)]
(unreduced (unreduced-> ~acc
~@(map (fn [[k v]] `(~body-rf ~k ~v)) expr))))
`(let [~body-rf (fn [~acc ~binding] ~body)]
(unreduced (unreduced-> ~acc
~@(map (fn [v] `(~body-rf ~v)) expr))))))
(if (destructuring-pair? binding)
`(let [expr# ~expr]
(if (and (map? expr#) (kvreducible? expr#))
(core/reduce-kv (fn [~acc ~@binding] ~body) ~acc expr#)
(core/reduce (fn [~acc ~binding] ~body) ~acc expr#)))
`(core/reduce (fn [~acc ~binding] ~body) ~acc ~expr))))
`(core/reduce (fn [~acc ~binding] ~body) ~acc ~expr)))))
init rpairs))
nested-reduceds (core/for [[expr binding] rpairs
:when (not (keyword? binding))]