Category talk:Wren-seq: Difference between revisions

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     // As 'sortPart' above but uses the default comparer: {|i, j| i < j }.
     static sortPart(a, start, end) { sortPart(a, start, end) {|i, j| i < j } }
+    // Returns a list of numbers between 'start' and 'end' inclusive
+    // having a positive step of 'step' between successive numbers.
+    // If 'ascend' is true, the numbers are incremented by 'step'
+    // otherwise they are decremented by 'step'.
+    // If `ascend' is true and start > end, an empty list is returned.
+    // If 'ascend' is false and start < end, an empty list is returned.
+    static between(start, end, step, ascend) {
+        if (step <= 0) Fiber.abort("Step must be a positive number.")
+        if ((start > end && ascend) || (start < end && !ascend)) return []
+        var lst = []
+        var i = start
+        if (ascend) {
+            while (i <= end) {
+                lst.add(i)
+                i = i + step
+            }
+        } else {
+            while (i >= end) {
+                lst.add(i)
+                i = i - step
+            }
+        }
+        return lst
+    }
+    // Convenience versions of the above method which use default values for some parameters.
+    static between(start, end, step) { between(start, end, step, start <= end) }
+    static between(start, end)       { between(start, end, 1, start <= end)    }
 }