From 3baa7c12a503efeee9e4d19e6ad9ca0fcd6242ea Mon Sep 17 00:00:00 2001
From: Simon Brooke <simon@journeyman.cc>
Date: Sun, 30 Sep 2018 14:38:57 +0100
Subject: [PATCH] Order-preserving-set
---
src/adl_support/rest_support.clj | 14 +++++---------
src/adl_support/utils.clj | 14 ++++++++++++++
test/adl_support/utils_test.clj | 6 ++++++
3 files changed, 25 insertions(+), 9 deletions(-)
diff --git a/src/adl_support/rest_support.clj b/src/adl_support/rest_support.clj
index 56c1ade..8f6cafa 100644
--- a/src/adl_support/rest_support.clj
+++ b/src/adl_support/rest_support.clj
@@ -46,10 +46,10 @@
;; TODO: candidate for moving to adl-support.core
[form request]
`(if-valid-user
- ~form
- ~request
- {:status 403
- :body (json/write-str "You must be logged in to do that")}))
+ ~form
+ ~request
+ {:status 403
+ :body (json/write-str "You must be logged in to do that")}))
(defmacro with-params-or-error
@@ -64,9 +64,6 @@
:body (json/write-str (str "The following params are required: " ~required))}))
-;; (with-params-or-error (/ 1 0) {:a 1 :b 2} #{:a :b :c})
-;; (with-params-or-error "hello" {:a 1 :b 2} #{:a :b })
-
(defmacro do-or-server-fail
"Evaluate this `form`; if it succeeds, return an HTTP response with this
status code and the JSON-formatted result as body; if it fails, return an
@@ -78,6 +75,5 @@
{:status ~status
:body (:result r#)}
{:status 500
- :body r#})))
-
+ :body r#})))
diff --git a/src/adl_support/utils.clj b/src/adl_support/utils.clj
index b22cbf1..2d1b8d2 100644
--- a/src/adl_support/utils.clj
+++ b/src/adl_support/utils.clj
@@ -658,3 +658,17 @@
0
(expt 10 v)))
(catch Exception _ 0)))
+
+
+(defn order-preserving-set
+ "The Clojure `set` function does not preserve the order in which elements are
+ passed to it. This function is like `set`, except
+ 1. It returns a list, not a hashset, and
+ 2. It is order-preserving."
+ [collection]
+ (loop [lhs (list (first collection))
+ rhs (rest collection)]
+ (cond
+ (empty? rhs) (reverse lhs)
+ (some #(= (first rhs) %) lhs) (recur lhs (rest rhs))
+ true (recur (cons (first rhs) lhs) (rest rhs)))))
diff --git a/test/adl_support/utils_test.clj b/test/adl_support/utils_test.clj
index 4499eb7..5132672 100644
--- a/test/adl_support/utils_test.clj
+++ b/test/adl_support/utils_test.clj
@@ -598,3 +598,9 @@
(is (= (key-names e2) #{"id" "shard"}))
(is (= (key-names e2 true) #{:id :shard})))))
+
+(deftest order-preserving-set-tests
+ (testing "order-preserving-set"
+ (is (= '(:a) (order-preserving-set '(:a :a :a :a))))
+ (is (= '(:a) (order-preserving-set [:a :a :a :a])))
+ (is (= '(:a :b :c :d :e) (order-preserving-set '(:a :a :b :c :a :b :d :c :e))))))