Import specs for while and until

Most of them are passing, a few issues with `redo` had to be disabled
due to infinite loops.

spec/language/until_spec.rb

@@ -0,0 +1,237 @@
+require_relative '../spec_helper'
+
+# until bool-expr [do]
+#   body
+# end
+#
+# begin
+#   body
+# end until bool-expr
+#
+# expr until bool-expr
+describe "The until expression" do
+  it "runs while the expression is false" do
+    i = 0
+    until i > 9
+      i += 1
+    end
+
+    i.should == 10
+  end
+
+  it "optionally takes a 'do' after the expression" do
+    i = 0
+    until i > 9 do
+      i += 1
+    end
+
+    i.should == 10
+  end
+
+  it "allows body begin on the same line if do is used" do
+    i = 0
+    until i > 9 do i += 1
+    end
+
+    i.should == 10
+  end
+
+  it "executes code in containing variable scope" do
+    i = 0
+    until i == 1
+      a = 123
+      i = 1
+    end
+
+    a.should == 123
+  end
+
+  it "executes code in containing variable scope with 'do'" do
+    i = 0
+    until i == 1 do
+      a = 123
+      i = 1
+    end
+
+    a.should == 123
+  end
+
+  it "returns nil if ended when condition became true" do
+    i = 0
+    until i > 9
+      i += 1
+    end.should == nil
+  end
+
+  it "evaluates the body if expression is empty" do
+    a = []
+    until ()
+      a << :body_evaluated
+      break
+    end
+    a.should == [:body_evaluated]
+  end
+
+  it "stops running body if interrupted by break" do
+    i = 0
+    until i > 9
+      i += 1
+      break if i > 5
+    end
+    i.should == 6
+  end
+
+  it "returns value passed to break if interrupted by break" do
+    until false
+      break 123
+    end.should == 123
+  end
+
+  it "returns nil if interrupted by break with no arguments" do
+    until false
+      break
+    end.should == nil
+  end
+
+  it "skips to end of body with next" do
+    a = []
+    i = 0
+    until (i+=1)>=5
+      next if i==3
+      a << i
+    end
+    a.should == [1, 2, 4]
+  end
+
+  # NATFIXME: Infinite loop
+  xit "restarts the current iteration without reevaluating condition with redo" do
+    a = []
+    i = 0
+    j = 0
+    until (i+=1)>=3
+      a << i
+      j+=1
+      redo if j<3
+    end
+    a.should == [1, 1, 1, 2]
+  end
+end
+
+describe "The until modifier" do
+  it "runs preceding statement while the condition is false" do
+    i = 0
+    i += 1 until i > 9
+    i.should == 10
+  end
+
+  it "evaluates condition before statement execution" do
+    a = []
+    i = 0
+    a << i until (i+=1) >= 3
+    a.should == [1, 2]
+  end
+
+  it "does not run preceding statement if the condition is true" do
+    i = 0
+    i += 1 until true
+    i.should == 0
+  end
+
+  it "returns nil if ended when condition became true" do
+    i = 0
+    (i += 1 until i>9).should == nil
+  end
+
+  it "returns value passed to break if interrupted by break" do
+    (break 123 until false).should == 123
+  end
+
+  it "returns nil if interrupted by break with no arguments" do
+    (break until false).should == nil
+  end
+
+  it "skips to end of body with next" do
+    i = 0
+    j = 0
+    ((i+=1) == 3 ? next : j+=i) until i > 10
+    j.should == 63
+  end
+
+  # NATFIXME: Infinite loop
+  xit "restarts the current iteration without reevaluating condition with redo" do
+    i = 0
+    j = 0
+    (i+=1) == 4 ? redo : j+=i until (i+=1) > 10
+    j.should == 34
+  end
+end
+
+describe "The until modifier with begin .. end block" do
+  it "runs block while the expression is false" do
+    i = 0
+    begin
+      i += 1
+    end until i > 9
+
+    i.should == 10
+  end
+
+  it "stops running block if interrupted by break" do
+    i = 0
+    begin
+      i += 1
+      break if i > 5
+    end until i > 9
+
+    i.should == 6
+  end
+
+  it "returns value passed to break if interrupted by break" do
+    (begin; break 123; end until false).should == 123
+  end
+
+  it "returns nil if interrupted by break with no arguments" do
+    (begin; break; end until false).should == nil
+  end
+
+  it "runs block at least once (even if the expression is true)" do
+    i = 0
+    begin
+      i += 1
+    end until true
+
+    i.should == 1
+  end
+
+  it "evaluates condition after block execution" do
+    a = []
+    i = 0
+    begin
+      a << i
+    end until (i+=1)>=5
+    a.should == [0, 1, 2, 3, 4]
+  end
+
+  it "skips to end of body with next" do
+    a = []
+    i = 0
+    begin
+      next if i==3
+      a << i
+    end until (i+=1)>=5
+    a.should == [0, 1, 2, 4]
+  end
+
+  # NATFIXME: Infinite loop
+  xit "restart the current iteration without reevaluating condition with redo" do
+    a = []
+    i = 0
+    j = 0
+    begin
+      a << i
+      j+=1
+      redo if j<3
+    end until (i+=1)>=3
+    a.should == [0, 0, 0, 1, 2]
+  end
+end