Merge pull request #1615 from actonlang/default-args-range

Set range default step=1

base/builtin/range.c

@@ -26,13 +26,14 @@ B_NoneType B_rangeD___init__(B_range self, B_int start, B_int stop, B_int step)
     }
     if (step) {
         int stp = from$int(step);
-        if (stp==0) {
-            $RAISE((B_BaseException)$NEW(B_ValueError,to$str("step size zero in range")));
-        }
-        else
+        if (stp == 0) {
+            $RAISE((B_BaseException)$NEW(B_ValueError, to$str("range() step size must not be zero")));
+        } else {
             self->step = stp;
-    } else
+        }
+    } else {
         self->step = 1;
+    }
     return B_None;
 }
 

base/src/__builtin__.act

@@ -81,7 +81,17 @@ class list[A] (object):
         NotImplemented
 
 class range (value):
-    def __init__(self, start: int, stop: ?int, step: ?int) -> None:
+    """Return an object that produces a sequence of integers from start
+    (inclusive) to stop (exclusive) in step sizes as specified by the step
+    argument, which is 1 per default. It is possible to call with just a single
+    argument like `range(j)` where `j` is then interpreted to be the stop
+    argument with an implicit default start of 0.
+
+    - `range(0, 3, 1)` produces [0, 1, 2]
+    - `range(0, 3)` produces [0, 1, 2]
+    - `range(3)` produces [0, 1, 2]
+    """
+    def __init__(self, start: int, stop: ?int, step: int=1) -> None:
         NotImplemented
 
 class Iterator[A] (object):