add _.range

lib/underscore.lua

@@ -45,6 +45,20 @@ function Underscore.iter(list_or_iter)
 	end)
 end
 
+function Underscore.range(start_i, end_i, step)
+	if end_i == nil then
+		end_i = start_i
+		start_i = 1
+	end
+	step = step or 1
+	local range_iter = coroutine.wrap(function() 
+		for i=start_i, end_i, step do
+			coroutine.yield(i)
+		end
+	end)
+	return Underscore:new(range_iter)
+end
+
 --- Identity function. This function looks useless, but is used throughout Underscore as a default.
 -- @name _.identity
 -- @param value any object

spec/range_spec.lua

@@ -0,0 +1,50 @@
+require 'luaspec'
+_ = require 'underscore'
+
+describe["_.range"] = function()
+	describe["when only passing a length"] = function()
+		it["should iterate from 1 to the length"] = function()
+			result = _.range(3):to_array()
+			expect(#result).should_be(3)
+			expect(result[1]).should_be(1)
+			expect(result[2]).should_be(2)
+			expect(result[3]).should_be(3)
+		end
+	end
+
+	describe["when only passing a start and end value"] = function()
+		it["should iterate from start to the end inclusively"] = function()
+			result = _.range(2,4):to_array()
+			expect(#result).should_be(3)
+			expect(result[1]).should_be(2)
+			expect(result[2]).should_be(3)
+			expect(result[3]).should_be(4)
+		end
+	end
+
+	describe["when passing a start and end value and a step"] = function()
+		describe["when step is positive"] = function()
+			it["should iterate from start to the end inclusively incremented by step"] = function()
+				result = _.range(2,6,2):to_array()
+				expect(#result).should_be(3)
+				expect(result[1]).should_be(2)
+				expect(result[2]).should_be(4)
+				expect(result[3]).should_be(6)
+			end
+		end
+
+		describe["when step is negative"] = function()
+			it["should iterate from start to the end inclusively decremented by step"] = function()
+				result = _.range(6,2,-2):to_array()
+				expect(#result).should_be(3)
+				expect(result[1]).should_be(6)
+				expect(result[2]).should_be(4)
+				expect(result[3]).should_be(2)
+			end
+		end
+	end
+
+end
+
+
+spec:report(true)