Refactored calculator examples.

Added ability to interpret unary operators.

examples/calc.citrus

@@ -1,6 +1,6 @@
-# A grammar for mathematical formulas that apply the basic four operations to
-# non-negative numbers (integers and floats), respecting operator precedence and
-# ignoring whitespace.
+# A grammar for mathematical formulas that apply basic mathematical operations
+# to all numbers, respecting operator precedence and grouping of expressions
+# while ignoring whitespace.
 #
 # An identical grammar that is written using pure Ruby can be found in calc.rb.
 grammar Calc
@@ -20,13 +20,25 @@ grammar Calc
   end
 
   rule factor
-    multiplicative | exponent
+    multiplicative | prefix
   end
 
   rule multiplicative
-    (exponent multiplicative_operator factor) {
+    (prefix multiplicative_operator factor) {
       def value
-        multiplicative_operator.apply(primary.value, factor.value)
+        multiplicative_operator.apply(prefix.value, factor.value)
+      end
+    }
+  end
+
+  rule prefix
+    prefixed | exponent
+  end
+
+  rule prefixed
+    (unary_operator prefix) {
+      def value
+        unary_operator.apply(prefix.value)
       end
     }
   end
@@ -83,24 +95,34 @@ grammar Calc
 
   rule additive_operator
     (('+' | '-') space) {
-      def apply(factor, term)
-        factor.send(text.strip, term)
+      def apply(n1, n2)
+        n1.send(text.strip, n2)
       end
     }
   end
 
   rule multiplicative_operator
     (('*' | '/' | '%') space) {
-      def apply(primary, factor)
-        primary.send(text.strip, factor)
+      def apply(n1, n2)
+        n1.send(text.strip, n2)
       end
     }
   end
 
   rule exponential_operator
     ('**' space) {
-      def apply(primary, exponent)
-        primary ** exponent
+      def apply(n1, n2)
+        n1 ** n2
+      end
+    }
+  end
+
+  rule unary_operator
+    (('~' | '+' | '-') space) {
+      def apply(n)
+        op = text.strip
+        # Unary + and - require an @.
+        n.send(op == '~' ? op : '%s@' % op)
       end
     }
   end

examples/calc.rb

@@ -1,8 +1,8 @@
 require 'citrus'
 
-# A grammar for mathematical formulas that apply the basic four operations to
-# non-negative numbers (integers and floats), respecting operator precedence and
-# ignoring whitespace.
+# A grammar for mathematical formulas that apply basic mathematical operations
+# to all numbers, respecting operator precedence and grouping of expressions
+# while ignoring whitespace.
 #
 # An identical grammar that is written using Citrus' own grammar syntax can be
 # found in calc.citrus.
@@ -23,13 +23,25 @@ def value
   end
 
   rule :factor do
-    any(:multiplicative, :exponent)
+    any(:multiplicative, :prefix)
   end
 
   rule :multiplicative do
-    all(:exponent, :multiplicative_operator, :factor) {
+    all(:prefix, :multiplicative_operator, :factor) {
       def value
-        multiplicative_operator.apply(primary.value, factor.value)
+        multiplicative_operator.apply(prefix.value, factor.value)
+      end
+    }
+  end
+
+  rule :prefix do
+    any(:prefixed, :exponent)
+  end
+
+  rule :prefixed do
+    all(:unary_operator, :prefix) {
+      def value
+        unary_operator.apply(prefix.value)
       end
     }
   end
@@ -86,24 +98,34 @@ def value
 
   rule :additive_operator do
     all(any('+', '-'), :space) {
-      def apply(factor, term)
-        factor.send(text.strip, term)
+      def apply(n1, n2)
+        n1.send(text.strip, n2)
       end
     }
   end
 
   rule :multiplicative_operator do
     all(any('*', '/', '%'), :space) {
-      def apply(primary, factor)
-        primary.send(text.strip, factor)
+      def apply(n1, n2)
+        n1.send(text.strip, n2)
       end
     }
   end
 
   rule :exponential_operator do
     all('**', :space) {
-      def apply(primary, exponent)
-        primary ** exponent
+      def apply(n1, n2)
+        n1 ** n2
+      end
+    }
+  end
+
+  rule :unary_operator do
+    all(any('~', '+', '-'), :space) {
+      def apply(n)
+        op = text.strip
+        # Unary + and - require an @.
+        n.send(op == '~' ? op : '%s@' % op)
       end
     }
   end

test/helper.rb

@@ -121,5 +121,29 @@ def test_exponent
     def test_exponent_float
       do_test('2**2.2')
     end
+
+    def test_negative
+      do_test('-5')
+    end
+
+    def test_double_negative
+      do_test('--5')
+    end
+
+    def test_complement
+      do_test('~4')
+    end
+
+    def test_double_complement
+      do_test('~~4')
+    end
+
+    def test_mixed_unary
+      do_test('~-4')
+    end
+
+    def test_complex_with_negatives
+      do_test('4 * -7 / (8.0 + 1_2)**2')
+    end
   end
 end