Pairwise operator

.gitignore

@@ -9,8 +9,11 @@
 .shadow-cljs
 .yarn/*
 /*-init.clj
+/.calva
+/.clj-kondo
 /.cpcache
 /.lein-*
+/.lsp
 /.nrepl-port
 /.rebel*
 /checkouts

CONTRIBUTING.md

@@ -11,3 +11,13 @@ statement:
     the public at large and to the detriment of our heirs and successors. We
     intend this dedication to be an overt act of relinquishment in perpetuity of
     all present and future rights to this code under copyright law.
+
+## Running tests
+
+To run the tests, install yarn and execute:
+
+```
+yarn run test
+```
+
+This will compile the cljs code and run the tests.

src/beicon/v2/core.cljs

@@ -222,7 +222,7 @@
 }" rx/combineLatest))
 
 (defn combine-latest-all
-  "Comboines multiple Observables to create an Observable whose values
+  "Combines multiple Observables to create an Observable whose values
   are calculated from the latest values of each of its input
   Observables (constructor).
 
@@ -489,6 +489,12 @@
   ([f seed ob]
    (ops/pipe (ops/reduce f seed) ob)))
 
+(defn pairwise
+  "Groups pairs of consecutive emssions together and emits them as
+  a javascript array."
+  [ob]
+  (ops/pipe (ops/pairwise) ob))
+
 (defn scan
   "Applies an accumulator function over an observable sequence and
   returns each intermediate result.  Same as reduce but with

src/beicon/v2/operators.cljs

@@ -130,6 +130,11 @@
   ([f seed]
    (rx/reduce #(f %1 %2) seed)))
 
+(def ^function pairwise
+  "Groups pairs of consecutive emssions together and emits them as
+   a javascript array."
+  rx/pairwise)
+
 (defn scan
   "Applies an accumulator function over an observable sequence and
   returns each intermediate result.  Same as reduce but with

test/beicon/tests/v2_test.cljs

@@ -254,6 +254,13 @@
       (drain! s #(do (t/is (= % [[1 2 4 5 6]]))
                      (done))))))
 
+(t/deftest observable-pairwise
+  (t/async done
+           (let [s (rx/from [1 2 3 4 5])
+                 ps (rx/pairwise s)]
+             (t/is (rx/observable? ps))
+             (drain! ps #(t/is (= (map vec %) [[1 2] [2 3] [3 4] [4 5]])))
+             (rx/on-end ps done))))
 
 (t/deftest observable-scan
   (t/async done