Implement Array#fetch() with test.

Signed-off-by: Ted Reed <ted.reed@gmail.com>

Rakefile

@@ -245,6 +245,7 @@ namespace :test do |ns|
         test "array/delete.t"
         test "array/empty.t"
         test "array/equals.t"
+        test "array/fetch.t"
         test "array/fill.t"
         test "array/first.t"
         test "array/flatten.t"
@@ -265,7 +266,7 @@ namespace :test do |ns|
         test "array/values_at.t"
         test "array/warray.t"
 
-        task :all => [:array, :at, :clear, :collect, :compact, :concat, :delete, :empty, :equals, :fill, :first, :flatten, :grep, :include, :index, :intersection, :join, :mathop, :pop, :reject, :reverse, :shift, :slice, :sort, :to_s, :uniq, :values_at, :warray]
+        task :all => [:array, :at, :clear, :collect, :compact, :concat, :delete, :empty, :equals, :fetch, :fill, :first, :flatten, :grep, :include, :index, :intersection, :join, :mathop, :pop, :reject, :reverse, :shift, :slice, :sort, :to_s, :uniq, :values_at, :warray]
     end
 
     namespace :file do 

src/classes/Array.pir

@@ -1,4 +1,4 @@
-## $Id$
+# $Id$
 
 =head1 NAME
 
@@ -1448,6 +1448,43 @@ The zip operator.
    .return (values)
 .end
 
+.sub 'fetch' :method
+    .param int index 
+    .param pmc default_value      :optional
+    .param int has_default_value  :opt_flag
+    .param pmc default_block      :optional :named('!BLOCK')
+    .param int has_default_block  :opt_flag
+    .local int length
+
+    $I0 = has_default_block + has_default_value
+    if $I0 > 1 goto incorrect_args
+
+    length = elements self
+
+    if index >= length goto out_of_bounds
+    $I0 = index
+    if index >= 0 goto skip_negative
+    $I0 = index + length
+    if index < 0 goto out_of_bounds
+
+  skip_negative:
+    $P0=self[$I0]
+    .return ( $P0 )
+
+  out_of_bounds:
+    if has_default_block goto do_block # block supersedes default value
+    if has_default_value goto do_value
+# TODO: throw exception IndexError
+    .return ( index )
+  do_value:
+    .return ( default_value )
+  do_block:
+    $P0=default_block( index )
+    .return ( $P0 )
+  incorrect_args:
+# TODO: pass warning
+.end
+
 .sub '_cmp' :vtable('cmp') :method
     .param pmc other
     .local int i, len, result

t/array/fetch.t

@@ -0,0 +1,24 @@
+require 'Test'
+include Test
+plan 8
+
+a = [ 1, 2, 3, 4 ]
+
+is a.fetch(0), 1, 'fetch, valid lookup'
+is a.fetch(3), 4, 'fetch, valid lookup'
+# TODO is a.fetch(5) throws IndexError exception
+
+is a.fetch(3, 5), 4,         'fetch, valid lookup, default value'
+is a.fetch(5, 5), 5,         'fetch, out of bounds, default value'
+is a.fetch(5, 'cat'), 'cat', 'fetch, out of bounds, default value'
+
+b=a.fetch(3) {|x| x*x }
+is b, 4, 'fetch, valid lookup, default block'
+
+b=a.fetch(5) {|x| 'dog' }
+is b, 'dog', 'fetch, out of bounds, default block'
+
+b=a.fetch(5) {|x| x*x }
+is b, 25, 'fetch, out of bounds, default block'
+
+