erlang: list comprehensions (+12 tests)

lib/erlang/tests/eval.sx

@@ -902,6 +902,41 @@
       (nm (if (er-atom? reason) reason (nth (get reason :elements) 0)))))
   "badarg")
 
+;; ── list comprehensions ───────────────────────────────────────
+(er-eval-test "lc map double"
+  (ev "hd([X * 2 || X <- [1, 2, 3]])") 2)
+(er-eval-test "lc map sum"
+  (ev "lists:foldl(fun (X, Acc) -> X + Acc end, 0, [X * 2 || X <- [1, 2, 3]])")
+  12)
+(er-eval-test "lc length"
+  (ev "length([X || X <- [1, 2, 3, 4, 5]])") 5)
+(er-eval-test "lc filter sum"
+  (ev "lists:foldl(fun (X, Acc) -> X + Acc end, 0, [X || X <- [1, 2, 3, 4, 5], X rem 2 =:= 0])")
+  6)
+(er-eval-test "lc filter only"
+  (ev "length([X || X <- [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], X > 5])")
+  5)
+(er-eval-test "lc empty source"
+  (get (ev "[X || X <- []]") :tag) "nil")
+(er-eval-test "lc all filtered"
+  (get (ev "[X || X <- [1, 2, 3], X > 100]") :tag) "nil")
+(er-eval-test "lc cartesian length"
+  (ev "length([{X, Y} || X <- [1, 2, 3], Y <- [a, b]])")
+  6)
+(er-eval-test "lc pattern match"
+  (ev "lists:foldl(fun (X, Acc) -> X + Acc end, 0, [V || {ok, V} <- [{ok, 1}, {error, x}, {ok, 2}, {ok, 3}]])")
+  6)
+(er-eval-test "lc nested generators"
+  (ev "length([{X, Y} || X <- [1, 2, 3], Y <- [10, 20, 30], X + Y > 12])")
+  7)
+(er-eval-test "lc squares"
+  (ev "lists:foldl(fun (X, Acc) -> X + Acc end, 0, [X*X || X <- [1, 2, 3, 4, 5]])")
+  55)
+;; First {ok, X} tuple: head of [{ok,a}, {ok,b}] is {ok, a}.
+(er-eval-test "lc tuple capture"
+  (nm (nth (get (get (ev "[{ok, X} || X <- [a, b]]") :head) :elements) 0))
+  "ok")
+
 (define
   er-eval-test-summary
   (str "eval " er-eval-test-pass "/" er-eval-test-count))