Slice and Splice tests are back on master.

Author: jashkenas

lib/grammar.js

@@ -245,6 +245,7 @@ grammar =
     o ':: Identifier',                          -> new Accessor $2, 'proto'
     o '::',                                     -> new Accessor new Literal 'prototype'
     o 'Index'
+    o 'Slice',                                  -> new Slice $1
   ]
 
   # Indexing into an object or array using bracket notation.

lib/nodes.js

@@ -871,6 +871,7 @@ exports.Assign = class Assign extends Base
   compileNode: (o) ->
     if isValue = @variable instanceof Value
       return @compilePatternMatch o if @variable.isArray() or @variable.isObject()
+      return @compileSplice       o if @variable.isSplice()
       return @compileConditional  o if @context in ['||=', '&&=', '?=']
     name = @variable.compile o, LEVEL_LIST
     if @value instanceof Code and match = @METHOD_DEF.exec name

lib/parser.js

@@ -16,14 +16,34 @@ ok odds.join(' ')  is "one! three!"
 
 # Basic range comprehensions.
 nums = (i * 3 for i in [1..3])
+
 negs = (x for x in [-20..-5*2])
-eq nums.concat(negs.slice 0, 3).join(' '), '3 6 9 -20 -19 -18'
+negs = negs[0..2]
+
+result = nums.concat(negs).join(', ')
+
+ok result is '3, 6, 9, -20, -19, -18'
 
 
 # With range comprehensions, you can loop in steps.
-eq "#{ x for x in [0..9] by  3 }", '0,3,6,9'
-eq "#{ x for x in [9..0] by -3 }", '9,6,3,0'
-eq "#{ x for x in [3*3..0*0] by 0-3 }", '9,6,3,0'
+results = (x for x in [0...15] by 5)
+ok results.join(' ') is '0 5 10'
+
+results = (x for x in [0..100] by 10)
+ok results.join(' ') is '0 10 20 30 40 50 60 70 80 90 100'
+
+
+# And can loop downwards, with a negative step.
+results = (x for x in [5..1])
+
+ok results.join(' ') is '5 4 3 2 1'
+ok results.join(' ') is [(10-5)..(-2+3)].join(' ')
+
+results = (x for x in [10..1])
+ok results.join(' ') is [10..1].join(' ')
+
+results = (x for x in [10...0] by -2)
+ok results.join(' ') is [10, 8, 6, 4, 2].join(' ')
 
 
 # Range comprehension gymnastics.
@@ -110,6 +130,11 @@ results = for i in [1..3]
 ok results.join(', ') is '3  , 3 6 , 3 6 9'
 
 
+# Naked ranges are expanded into arrays.
+array = [0..10]
+ok(num % 2 is 0 for num in array by 2)
+
+
 # Nested comprehensions.
 multiLiner =
   for x in [3..5]
@@ -153,6 +178,11 @@ ok own.join(' ') is 'Whiskers'
 ok all.sort().join(' ') is 'Whiskers cream tabby'
 
 
+# Optimized range comprehensions.
+exxes = ('x' for [0...10])
+ok exxes.join(' ') is 'x x x x x x x x x x'
+
+
 # Comprehensions safely redeclare parameters if they're not present in closest
 # scope.
 rule = (x) -> x

src/grammar.coffee

@@ -0,0 +1,74 @@
+# # Slice.
+array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+a = array[7..9]
+b = array[2...4]
+
+result = a.concat(b).join(' ')
+
+ok result is "7 8 9 2 3"
+
+a = [0, 1, 2, 3, 4, 5, 6, 7]
+eq a[2...6].join(' '), '2 3 4 5'
+
+
+# Ranges.
+countdown = [10..1].join(' ')
+ok countdown is "10 9 8 7 6 5 4 3 2 1"
+
+a = 1
+b = 5
+nums = [a...b]
+ok nums.join(' ') is '1 2 3 4'
+
+b = -5
+nums = [a..b]
+ok nums.join(' ') is '1 0 -1 -2 -3 -4 -5'
+
+
+# Expression-based range.
+array = [(1+5)..1+9]
+ok array.join(' ') is "6 7 8 9 10"
+
+array = [5..1]
+ok array.join(' ') is '5 4 3 2 1'
+
+array = [30...0]
+ok (len = array.length) is 30
+ok array[len - 1] is 1
+
+
+
+# String slicing (at least on Node).
+hello = "Hello World"
+
+ok hello[1...1] is ""
+ok hello[1..1] is "e"
+ok hello[1...5] is "ello"
+ok hello[0..4] is "Hello"
+
+
+# Splice literals.
+array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+
+array[5..10] = [0, 0, 0]
+
+ok array.join(' ') is '0 1 2 3 4 0 0 0'
+
+
+# Slices and splices that omit their beginning or end.
+array = [0..10]
+
+ok array[7..].join(' ')  is '7 8 9 10'
+ok array[-2..].join(' ') is '9 10'
+
+ok array[...3].join(' ') is '0 1 2'
+ok array[..-5].join(' ') is '0 1 2 3 4 5 6'
+
+array[3..] = [9, 8, 7]
+
+ok array.join(' ') is '0 1 2 9 8 7'
+
+array[...3] = [7, 8, 9]
+
+ok array.join(' ') is '7 8 9 9 8 7'