Implement Left and Right parsers

1 files changed, 32 insertions, 0 deletions

diff --git a/spec/parcom_spec.cr b/spec/parcom_spec.cr
index 77a14dd..d67f19a 100644
--- a/spec/parcom_spec.cr
+++ b/spec/parcom_spec.cr
@@ -308,6 +308,38 @@ describe Plus do
   end
 end
 
+# most behavior shouldn't need to be tested
+# since it is based on tested bbehavior from
+# Plus and Map
+describe Left do
+  describe "#parse" do
+    it "returns the value of the first parser if both succeed" do
+      tokens = TokenStream.from_string("testing")
+      letter_t = Token.new('t')
+      letter_e = Token.new('e')
+      result = (letter_t << letter_e).parse(tokens)
+
+      result.value.should eq('t')
+      result.tokens.should eq(tokens[2..])
+    end
+  end
+end
+
+# same deal as Left
+describe Right do
+  describe "#parse" do
+    it "returns the value of the second parser if both succeed" do
+      tokens = TokenStream.from_string("testing")
+      letter_t = Token.new('t')
+      letter_e = Token.new('e')
+      result = (letter_t >> letter_e).parse(tokens)
+
+      result.value.should eq('e')
+      result.tokens.should eq(tokens[2..])
+    end
+  end
+end
+
 describe Phrase do
   p = Phrase.new(Token.new('t'))