From: David Kerkeslager <kerkeslager@gmail.com>
Date: Sat, 5 Aug 2017 20:33:35 +0000 (-0400)
Subject: Add a negation operator
X-Git-Url: https://code.kerkeslager.com/?a=commitdiff_plain;h=fb83d523f8eb241d5ccafe8d391a9edd62150b48;p=fur

Add a negation operator
---

diff --git a/examples/08_negativity.fur b/examples/08_negativity.fur
new file mode 100644
index 0000000..7da32ad
--- /dev/null
+++ b/examples/08_negativity.fur
@@ -0,0 +1 @@
+print(-1)
diff --git a/examples/08_negativity.fur.output.txt b/examples/08_negativity.fur.output.txt
new file mode 100644
index 0000000..d7d17fc
--- /dev/null
+++ b/examples/08_negativity.fur.output.txt
@@ -0,0 +1 @@
+-1
\ No newline at end of file
diff --git a/generation.py b/generation.py
index 808b0d8..cefae7b 100644
--- a/generation.py
+++ b/generation.py
@@ -23,7 +23,10 @@ def generate_string_literal(c_string_literal):
         ''.join(c_escape(ch for ch in c_string_literal.value)),
     )
 
-def generate_argument(c_argument):
+def generate_expression(c_argument):
+    if isinstance(c_argument, transformation.CNegationExpression):
+        return generate_negation_expression(c_argument)
+
     if isinstance(c_argument, transformation.CFunctionCallExpression):
         return generate_function_call(c_argument)
 
@@ -45,14 +48,19 @@ def generate_argument(c_argument):
 
     return 'builtin${}({}, {})'.format(
         INFIX_TYPE_MAPPING[type(c_argument)],
-        generate_argument(c_argument.left),
-        generate_argument(c_argument.right),
+        generate_expression(c_argument.left),
+        generate_expression(c_argument.right),
+    )
+
+def generate_negation_expression(c_negation_expression):
+    return 'builtin$negate({})'.format(
+        generate_expression(c_negation_expression.value)
     )
 
 def generate_function_call(c_function_call):
     return '{}({})'.format(
         c_function_call.name,
-        ', '.join(generate_argument(argument) for argument in c_function_call.arguments),
+        ', '.join(generate_expression(argument) for argument in c_function_call.arguments),
     )
 
 def generate_statement(c_function_call_statement):
diff --git a/parsing.py b/parsing.py
index 1ab6df4..0d7caa6 100644
--- a/parsing.py
+++ b/parsing.py
@@ -44,6 +44,13 @@ FurStringLiteralExpression = collections.namedtuple(
     ],
 )
 
+FurNegationExpression = collections.namedtuple(
+    'FurNegationExpression',
+    [
+        'value',
+    ],
+)
+
 FurAdditionExpression = collections.namedtuple(
     'FurAdditionExpression',
     [
@@ -104,8 +111,22 @@ def _string_literal_expression_parser(index, tokens):
 
     return True, index, FurStringLiteralExpression(value=value)
 
+def _negation_expression_parser(index, tokens):
+    failure = (False, index, None)
+
+    if tokens[index].match != '-':
+        return failure
+
+    success, index, value = _literal_level_expression_parser(index + 1, tokens)
+
+    if not success:
+        return failure
+
+    return (True, index, FurNegationExpression(value=value))
+
 def _literal_level_expression_parser(index, tokens):
     return _or_parser(
+        _negation_expression_parser,
         _function_call_expression_parser,
         _integer_literal_expression_parser,
         _string_literal_expression_parser,
diff --git a/templates/program.c b/templates/program.c
index 063587d..64e0152 100644
--- a/templates/program.c
+++ b/templates/program.c
@@ -114,6 +114,16 @@ Object stringLiteral(Runtime* runtime, const char* literal)
 }
 
 // TODO Make this conditionally added
+Object builtin$negate(Object input)
+{
+  assert(input.type == INTEGER);
+
+  Object result;
+  result.type = INTEGER;
+  result.instance.integer = -input.instance.integer;
+  return result;
+}
+
 Object builtin$add(Object left, Object right)
 {
   assert(left.type == INTEGER);
diff --git a/transformation.py b/transformation.py
index 1fe7dc9..d680145 100644
--- a/transformation.py
+++ b/transformation.py
@@ -16,6 +16,13 @@ CStringLiteral = collections.namedtuple(
     ],
 )
 
+CNegationExpression = collections.namedtuple(
+    'CNegationExpression',
+    [
+        'value',
+    ],
+)
+
 CAdditionExpression = collections.namedtuple(
     'CAdditionExpression',
     [
@@ -79,6 +86,9 @@ BUILTINS = {
 }
 
 def transform_expression(builtin_dependencies, expression):
+    if isinstance(expression, parsing.FurNegationExpression):
+        return transform_negation_expression(builtin_dependencies, expression)
+
     if isinstance(expression, parsing.FurFunctionCallExpression):
         return transform_function_call_expression(builtin_dependencies, expression)
 
@@ -103,6 +113,9 @@ def transform_expression(builtin_dependencies, expression):
         right=transform_expression(builtin_dependencies, expression.right),
     )
 
+def transform_negation_expression(builtin_dependencies, negation_expression):
+    return CNegationExpression(value=transform_expression(builtin_dependencies, negation_expression.value))
+
 def transform_function_call_expression(builtin_dependencies, function_call):
     if function_call.name in BUILTINS.keys():
         builtin_dependencies.add(function_call.name)