From: David Kerkeslager <kerkeslager@gmail.com>
Date: Thu, 14 Sep 2017 23:06:05 +0000 (-0400)
Subject: Move desugaring ternary comparison operators into the normalization step
X-Git-Url: https://code.kerkeslager.com/?a=commitdiff_plain;h=3769b766b898b95fd699e3cb6d005576a4c22086;p=fur

Move desugaring ternary comparison operators into the normalization step
---

diff --git a/normalization.py b/normalization.py
index 2fa57fc..5b5bd94 100644
--- a/normalization.py
+++ b/normalization.py
@@ -431,12 +431,55 @@ def normalize_basic_infix_operation(counter, expression):
         NormalVariableExpression(variable=center_variable),
     )
 
-def normalize_comparison_expression(counter, expression):
-    stack = []
+def desugar_ternary_comparison(counter, expression):
+    counter, left_prestatements, left_expression = normalize_expression(counter, expression.left.left)
+    counter, middle_prestatements, middle_expression = normalize_expression(counter, expression.left.right)
+
+    left_variable = '${}'.format(counter)
+    counter += 1
+    middle_variable = '${}'.format(counter)
+    counter += 1
+
+    juncture_prestatements = (
+        NormalVariableInitializationStatement(
+            variable=left_variable,
+            expression=left_expression,
+        ),
+        NormalVariableInitializationStatement(
+            variable=middle_variable,
+            expression=middle_expression,
+        )
+    )
+
+    counter, boolean_expression_prestatements, boolean_expression =  normalize_boolean_expression(
+        counter,
+        parsing.FurInfixExpression(
+            order='and_level',
+            operator='and',
+            left=parsing.FurInfixExpression(
+                order='comparison_level',
+                operator=expression.left.operator,
+                left=NormalVariableExpression(variable=left_variable),
+                right=NormalVariableExpression(variable=middle_variable),
+            ),
+            right=parsing.FurInfixExpression(
+                order='comparison_level',
+                operator=expression.operator,
+                left=NormalVariableExpression(variable=middle_variable),
+                right=expression.right,
+            ),
+        )
+    )
+
+    return (
+        counter,
+        left_prestatements + middle_prestatements + juncture_prestatements + boolean_expression_prestatements,
+        boolean_expression,
+    )
 
-    while isinstance(expression.left, parsing.FurInfixExpression) and expression.order == 'comparison_level':
-        stack.append((expression.operator, expression.order, expression.right))
-        expression = expression.left
+def normalize_comparison_expression(counter, expression):
+    if isinstance(expression.left, parsing.FurInfixExpression) and expression.order == 'comparison_level':
+        return desugar_ternary_comparison(counter, expression)
 
     counter, left_prestatements, left_expression = normalize_expression(counter, expression.left)
     counter, right_prestatements, right_expression = normalize_expression(counter, expression.right)
@@ -468,29 +511,6 @@ def normalize_comparison_expression(counter, expression):
         ),
     )
 
-    while len(stack) > 0:
-        right_operator, right_order, right_expression = stack.pop()
-        and_right_expression = parsing.FurInfixExpression(
-            operator=right_operator,
-            order=right_order,
-            left=NormalVariableExpression(variable=right_variable),
-            right=right_expression,
-        )
-
-        and_expression = parsing.FurInfixExpression(
-            operator='and',
-            order='and_level',
-            left=result_expression,
-            right=and_right_expression,
-        )
-
-        counter, and_prestatements, result_expression = normalize_boolean_expression(
-            counter,
-            and_expression,
-        )
-
-        result_prestatements = result_prestatements + and_prestatements
-
     return (counter, result_prestatements, result_expression)
 
 def normalize_boolean_expression(counter, expression):
diff --git a/transformation.py b/transformation.py
index 82d4b3f..09a9b77 100644
--- a/transformation.py
+++ b/transformation.py
@@ -243,31 +243,6 @@ FUR_INFIX_OPERATOR_TO_C_INFIX_OPERATOR = {
 def transform_comparison_level_expression(accumulators, expression):
     accumulators.operator_set.add(FUR_INFIX_OPERATOR_TO_C_INFIX_OPERATOR[expression.operator])
 
-    # Transform expressions like 1 < 2 < 3 into expressions like 1 < 2 && 2 < 3
-    if isinstance(expression.left, parsing.FurInfixExpression) and expression.left.order == 'comparison_level':
-        left = transform_comparison_level_expression(
-            accumulators,
-            expression.left
-        )
-
-        middle = left.right
-
-        right = transform_expression(
-            accumulators,
-            expression.right,
-        )
-
-        # TODO Don't evaluate the middle expression twice
-        return CFunctionCallForFurInfixOperator(
-            name='and',
-            left=left,
-            right=CFunctionCallForFurInfixOperator(
-                name=FUR_INFIX_OPERATOR_TO_C_INFIX_OPERATOR[expression.operator].name,
-                left=middle,
-                right=right,
-            ),
-        )
-
     return CFunctionCallForFurInfixOperator(
         name=FUR_INFIX_OPERATOR_TO_C_INFIX_OPERATOR[expression.operator].name,
         left=transform_expression(accumulators, expression.left),