Issue #621. Added the ability to leave the start and end index off of arrays. list[5..] is now valid CoffeeScript, slicing to the end of the array.

lib/grammar.js

@@ -307,6 +307,14 @@
         return new RangeNode($2, $5);
       }), o("INDEX_START Expression . . . Expression INDEX_END", function() {
         return new RangeNode($2, $6, true);
+      }), o("INDEX_START Expression . . INDEX_END", function() {
+        return new RangeNode($2, null);
+      }), o("INDEX_START Expression . . . INDEX_END", function() {
+        return new RangeNode($2, null, true);
+      }), o("INDEX_START . . Expression INDEX_END", function() {
+        return new RangeNode(null, $4);
+      }), o("INDEX_START . . . Expression INDEX_END", function() {
+        return new RangeNode(null, $5, true);
       })
     ],
     Array: [

lib/nodes.js

@@ -692,11 +692,14 @@
     SliceNode.prototype["class"] = 'SliceNode';
     SliceNode.prototype.children = ['range'];
     SliceNode.prototype.compileNode = function(o) {
-      var from, plusPart, to;
-      from = this.range.from.compile(o);
-      to = this.range.to.compile(o);
-      plusPart = this.range.exclusive ? '' : ' + 1';
-      return ".slice(" + (from) + ", " + (to) + (plusPart) + ")";
+      var from, to;
+      from = this.range.from ? this.range.from.compile(o) : '0';
+      to = this.range.to ? this.range.to.compile(o) : '';
+      to += (!to || this.range.exclusive ? '' : ' + 1');
+      if (to) {
+        to = ', ' + to;
+      }
+      return ".slice(" + (from) + (to) + ")";
     };
     return SliceNode;
   })();
@@ -990,8 +993,8 @@
       l = this.variable.properties.length;
       range = this.variable.properties[l - 1].range;
       plus = range.exclusive ? '' : ' + 1';
-      from = range.from.compile(o);
-      to = range.to.compile(o) + ' - ' + from + plus;
+      from = range.from ? range.from.compile(o) : '0';
+      to = range.to ? range.to.compile(o) + ' - ' + from + plus : ("" + (name) + ".length");
       val = this.value.compile(o);
       return "" + (name) + ".splice.apply(" + (name) + ", [" + (from) + ", " + (to) + "].concat(" + (val) + "))";
     };

src/grammar.coffee

@@ -348,6 +348,10 @@ grammar =
   Slice: [
     o "INDEX_START Expression . . Expression INDEX_END", -> new RangeNode $2, $5
     o "INDEX_START Expression . . . Expression INDEX_END", -> new RangeNode $2, $6, true
+    o "INDEX_START Expression . . INDEX_END",   -> new RangeNode $2, null
+    o "INDEX_START Expression . . . INDEX_END", -> new RangeNode $2, null, true
+    o "INDEX_START . . Expression INDEX_END",   -> new RangeNode null, $4
+    o "INDEX_START . . . Expression INDEX_END", -> new RangeNode null, $5, true
   ]
 
   # The array literal.

src/nodes.coffee

@@ -621,10 +621,11 @@ exports.SliceNode = class SliceNode extends BaseNode
     super()
 
   compileNode: (o) ->
-    from     = @range.from.compile(o)
-    to       = @range.to.compile(o)
-    plusPart = if @range.exclusive then '' else ' + 1'
-    ".slice(#{from}, #{to}#{plusPart})"
+    from  =  if @range.from then @range.from.compile(o) else '0'
+    to    =  if @range.to then @range.to.compile(o) else ''
+    to    += if not to or @range.exclusive then '' else ' + 1'
+    to    =  ', ' + to if to
+    ".slice(#{from}#{to})"
 
 #### ObjectNode
 
@@ -860,8 +861,8 @@ exports.AssignNode = class AssignNode extends BaseNode
     l     = @variable.properties.length
     range = @variable.properties[l - 1].range
     plus  = if range.exclusive then '' else ' + 1'
-    from  = range.from.compile(o)
-    to    = range.to.compile(o) + ' - ' + from + plus
+    from  = if range.from then range.from.compile(o) else '0'
+    to    = if range.to then range.to.compile(o) + ' - ' + from + plus else "#{name}.length"
     val   = @value.compile(o)
     "#{name}.splice.apply(#{name}, [#{from}, #{to}].concat(#{val}))"
 

test/test_ranges_slices_and_splices.coffee

@@ -56,3 +56,20 @@ 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'
+