From 553f4bd7e6ffe8f27e868b7fb8a11bc0870babfa Mon Sep 17 00:00:00 2001 From: Darrick Wiebe Date: Tue, 10 Feb 2015 12:14:01 -0500 Subject: [PATCH] transducers --- .gitignore | 11 ++ LICENSE | 214 +++++++++++++++++++++++++++++++++ README.md | 14 +++ doc/intro.md | 3 + project.clj | 6 + src/transducers/core.clj | 64 ++++++++++ test/transducers/core_test.clj | 7 ++ 7 files changed, 319 insertions(+) create mode 100644 .gitignore create mode 100644 LICENSE create mode 100644 README.md create mode 100644 doc/intro.md create mode 100644 project.clj create mode 100644 src/transducers/core.clj create mode 100644 test/transducers/core_test.clj diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..c53038e --- /dev/null +++ b/.gitignore @@ -0,0 +1,11 @@ +/target +/classes +/checkouts +pom.xml +pom.xml.asc +*.jar +*.class +/.lein-* +/.nrepl-port +.hgignore +.hg/ diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..7689f30 --- /dev/null +++ b/LICENSE @@ -0,0 +1,214 @@ +THE ACCOMPANYING PROGRAM IS PROVIDED UNDER THE TERMS OF THIS ECLIPSE PUBLIC +LICENSE ("AGREEMENT"). 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Each party waives its rights to a jury trial +in any resulting litigation. diff --git a/README.md b/README.md new file mode 100644 index 0000000..a3301e0 --- /dev/null +++ b/README.md @@ -0,0 +1,14 @@ +# transducers + +A Clojure library designed to ... well, that part is up to you. + +## Usage + +FIXME + +## License + +Copyright © 2015 FIXME + +Distributed under the Eclipse Public License either version 1.0 or (at +your option) any later version. diff --git a/doc/intro.md b/doc/intro.md new file mode 100644 index 0000000..c1f5db1 --- /dev/null +++ b/doc/intro.md @@ -0,0 +1,3 @@ +# Introduction to transducers + +TODO: write [great documentation](http://jacobian.org/writing/what-to-write/) diff --git a/project.clj b/project.clj new file mode 100644 index 0000000..c80f41b --- /dev/null +++ b/project.clj @@ -0,0 +1,6 @@ +(defproject transducers "0.1.0-SNAPSHOT" + :description "FIXME: write description" + :url "http://example.com/FIXME" + :license {:name "Eclipse Public License" + :url "http://www.eclipse.org/legal/epl-v10.html"} + :dependencies [[org.clojure/clojure "1.7.0-alpha5"]]) diff --git a/src/transducers/core.clj b/src/transducers/core.clj new file mode 100644 index 0000000..41cd3cb --- /dev/null +++ b/src/transducers/core.clj @@ -0,0 +1,64 @@ +(ns transducers.core) + +(defn grouped-by + "A transducer that acts like (seq (group-by f coll)) or if you instantiate it + as (grouped-by f :keys? false) then it will act like (vals (group-by f coll))" + [f & {:keys [keys?] :or {keys? true}}] + (fn [rf] + (let [group (volatile! (transient (array-map)))] + (fn + ([] (rf)) + ([result] + (rf + (if keys? + (reduce rf result (persistent! @group)) + (reduce rf result (vals (persistent! @group)))))) + ([result x] + (vswap! group (fn [g] + (let [k (f x)] + (if-let [v (get g k)] + (assoc! g k (conj v x)) + (assoc! g k [x]))))) + result))))) + + +(defn branched-xform [pred true-x false-x] + (fn [rf] + (let [true-rf (true-x rf) + false-rf (false-x rf)] + (fn + ([] (true-rf) (false-rf)) + ([result] + (true-rf (false-rf result))) + ([result input] + (if (pred input) + (true-rf result input) + (false-rf result input))))))) + +(defn distinct-by [f] + (let [seen (volatile! (transient #{}))] + (filter (fn [x] + (let [y (f x)] + (when-not (@seen y) + (vswap! seen conj! y) + true)))))) + + +(defn lasts-by + "A transducer that accomplishes the following but more efficiently + (->> coll + (group_by f) + (map (fn [[k vals]] (last vals))))" + ([f] + (fn [rf] + (let [matches (volatile! (transient (array-map)))] + (fn + ([] (rf)) + ([result] (rf (reduce rf result (vals (persistent! @matches))))) + ([result x] + (vswap! matches assoc! (f x) x) + result))))) + ([f coll] + (sequence (lasts-by f) coll))) + + diff --git a/test/transducers/core_test.clj b/test/transducers/core_test.clj new file mode 100644 index 0000000..43f5f55 --- /dev/null +++ b/test/transducers/core_test.clj @@ -0,0 +1,7 @@ +(ns transducers.core-test + (:require [clojure.test :refer :all] + [transducers.core :refer :all])) + +(deftest a-test + (testing "FIXME, I fail." + (is (= 0 1))))