Make Parser.expression parse equality expressions

test/unit/lexer_unit_test.rb

@@ -26,10 +26,17 @@ class LexerUnitTest < Minitest::Test
     )
   end
 
+  def test_equality
+    assert_equal(
+      [[:equality, '=='], [:equality, '<>'], [:equality, '!='], [:end_of_string]],
+      tokenize('== <> != '),
+    )
+  end
+
   def test_comparison
     assert_equal(
-      [[:comparison, '=='], [:comparison, '<>'], [:comparison, 'contains'], [:end_of_string]],
-      tokenize('== <> contains '),
+      [[:comparison, '>'], [:comparison, '>='], [:comparison, '<'], [:comparison, '<='], [:comparison, 'contains'], [:end_of_string]],
+      tokenize('> >= < <= contains'),
     )
   end
 
@@ -81,7 +88,7 @@ class LexerUnitTest < Minitest::Test
 
   def test_whitespace
     assert_equal(
-      [[:id, 'five'], [:pipe, '|'], [:comparison, '=='], [:end_of_string]],
+      [[:id, 'five'], [:pipe, '|'], [:equality, '=='], [:end_of_string]],
       tokenize("five|\n\t =="),
     )
   end

test/unit/parser_unit_test.rb

@@ -77,6 +77,31 @@ class ParserUnitTest < Minitest::Test
     assert_equal(0..5, p.expression)
   end
 
+  def test_equality
+    p = new_parser("a == b")
+    expr = p.expression
+    assert(expr.is_a?(BinaryExpression))
+    assert_equal('==', expr.operator)
+    assert_equal('a', expr.left.name)
+    assert_equal('b', expr.right.name)
+
+    # BinaryExpression(==)
+    #   left: BinaryExpression(<)
+    #     left: 0
+    #     right: 5
+    #   right: BinaryExpression(>)
+    #     left: 6
+    #     right: 1
+    p = new_parser("0 < 5 == 6 > 1")
+    expr = p.expression
+    assert(expr.is_a?(BinaryExpression))
+    assert_equal('==', expr.operator)
+    assert_equal(0, expr.left.left)
+    assert_equal(5, expr.left.right)
+    assert_equal(6, expr.right.left)
+    assert_equal(1, expr.right.right)
+  end
+
   def test_comparison
     p = new_parser("a > b")
     expr = p.expression