Fix higher arities of the range function (#1006)

Fixes #1004

Author: chrisrink10

CHANGELOG.md

@@ -24,7 +24,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  * Fix an issue with `basilisp.core/time` failing when called outside `basilisp.core` (#991)
  * Fix an issue with `basilisp.core/promise` where a thread waiting for a value from another thread might not wake up immediately upon delivery (#983).
  * Fix using keyword as a function not returning the default value in some cases (#997)
- * Fix an issue where Python `SyntaxWarning`s would be emitted for certain compiled code (#???)
+ * Fix an issue where Python `SyntaxWarning`s would be emitted for certain compiled code (#996)
+ * Fix an issue where 2- and 3-arity `range` invocations returned unexpected results (#1004)
 
 ### Removed
  * Removed `python-dateutil` and `readerwriterlock` as dependencies, switching to standard library components instead (#976)

src/basilisp/core.lpy

@@ -2523,18 +2523,21 @@
 
 (defn range
   "Return a range of integers from ``start``\\. If ``end`` is specified, the sequence
-  will terminate at ``end``\\."
+  will terminate at ``end``\\. If ``step`` is specified, that amount will be added
+  for each iteration. ``step`` may be negative."
   ([]
    (iterate inc 0))
   ([end]
    (lazy-seq (cons 0 (range 1 end))))
   ([start end]
-   (lazy-seq (cons start (when (< start (dec end))
-                           (range (inc start) end)))))
+   (lazy-seq
+    (when (< start end)
+      (cons start (range (inc start) end)))))
   ([start end step]
-   (lazy-seq (let [next-int (+ start step)]
-               (cons start (when (< next-int (dec end))
-                             (range next-int end step)))))))
+   (lazy-seq
+    (when (or (and (>= step 0) (< start end))
+              (and (< step 0) (> start end)))
+      (cons start (range (+ start step) end step))))))
 
 (defn complement
   "Return a function which returns the logical complement of the return value of

tests/basilisp/core_test.py

@@ -1370,10 +1370,10 @@ def test_select_keys(self):
 
 
 def test_range():
-    assert llist.l(1) == core.range_(1, 1)
+    assert llist.EMPTY == core.range_(1, 1)
     assert llist.l(1, 2, 3, 4, 5) == core.range_(1, 6)
     assert llist.l(1, 3, 5, 7, 9) == core.range_(1, 11, 2)
-    # assert llist.l(1, -1, -3, -5, -7, -9) == core.range_(1, -10, -2)
+    assert llist.l(1, -1, -3, -5, -7, -9) == core.range_(1, -10, -2)
     assert 9999 == len(core.vec(core.range_(1, 10000)))
 
 

tests/basilisp/test_core_fns.lpy

@@ -710,6 +710,26 @@
       (run! #(swap! a + %) (range 5))
       (is (= @a 10)))))
 
+(deftest range-test
+  (testing "0-arity"
+    (is (= '(0 1 2 3 4) (take 5 (range)))))
+
+  (testing "1-arity"
+    (is (= '(0 1 2) (take 5 (range 3))))
+    (is (= '(0 1 2) (range 3)))
+    (is (= '(0 1 2 3 4) (take 5 (range 10)))))
+
+  (testing "2-arity"
+    (is (= '() (range 3 3)))
+    (is (= '(1 2 3) (range 1 4)))
+    (is (= '(1 2 3 4 5) (take 5 (range 1 10)))))
+
+  (testing "3-arity"
+    (is (= '() (range 3 3 2)))
+    (is (= '(1 4 7) (range 1 10 3)))
+    (is (= '(3 2 1) (range 3 0 -1)))
+    (is (= '(10 7 4 1) (range 10 0 -3)))))
+
 (deftest partial-test
   (testing "no arguments"
     (let [f-no-args (fn [] :no-args)]