Added if clause.

interpreter.py

@@ -275,8 +275,15 @@ class Interpreter():
             return cur
         elif isinstance(cur, nodes.BoolStatement):
             return cur
+        elif isinstance(cur, nodes.IfStatement):
+            return self.evaluate_if(cur)
+        elif isinstance(cur, nodes.AtomStatement):
+            varname = cur.get_value()
+            if varname in self.variables:
+                return self.variables[varname]
+            raise InvalidCode('Line %d: unknown variable "%s".' % (cur.lineno(), varname))
         else:
-            raise InvalidCode("Unknown statement in line %d." % cur.lineno())
+            raise InvalidCode("Line %d: Unknown statement." % cur.lineno())
 
     def validate_arguments(self, args, argcount, arg_types):
         if argcount is not None:
@@ -455,6 +462,15 @@ class Interpreter():
         if not isinstance(obj, InterpreterObject):
             raise InvalidArguments('Line %d: variable "%s" is not callable.' % (node.lineno(), object_name))
         return obj.method_call(method_name, self.reduce_arguments(args))
+    
+    def evaluate_if(self, node):
+        result = self.evaluate_statement(node.get_clause())
+        if isinstance(result, nodes.BoolExpression) or \
+           isinstance(result, nodes.BoolStatement):
+            if result.get_value():
+                self.evaluate_codeblock(node.get_codeblock())
+        else:
+            raise InvalidCode('Line %d: If clause does not evaluate to true or false.' % node.lineno())
 
 if __name__ == '__main__':
     code = """project('myawesomeproject')

nodes.py

@@ -66,6 +66,18 @@ class BoolStatement(Statement):
 
     def get_value(self):
         return self.value
+    
+class IfStatement(Statement):
+    def __init__(self, clause, codeblock, lineno):
+        Statement.__init__(self, lineno)
+        self.clause = clause
+        self.codeblock = codeblock
+
+    def get_clause(self):
+        return self.clause
+
+    def get_codeblock(self):
+        return self.codeblock
 
 class StringStatement(Statement):
     def __init__(self, value, lineno):

parser.py

@@ -19,7 +19,9 @@ import ply.yacc as yacc
 import nodes
 
 reserved = {'true' : 'TRUE',
-            'false' : 'FALSE'}
+            'false' : 'FALSE',
+            'if' : 'IF',
+            'endif' : 'ENDIF'}
 
 tokens = ['LPAREN',
           'RPAREN',
@@ -119,6 +121,10 @@ def p_statement_method_call(t):
     'statement : expression DOT expression LPAREN args RPAREN'
     t[0] = nodes.MethodCall(t[1], t[3], t[5], t.lineno(1))
 
+def p_statement_if(t):
+    'statement : IF LPAREN statement RPAREN EOL codeblock ENDIF'
+    t[0] = nodes.IfStatement(t[3], t[6], t.lineno(1))
+
 def p_statement_expression(t):
     'statement : expression'
     t[0] = nodes.statement_from_expression(t[1])

test cases/17 if/builder.txt

@@ -1,3 +1,14 @@
 project('if test', 'c')
 
-var = true
+var1 = true
+var2 = false
+
+if(var1)
+  exe = executable('prog', 'prog.c')
+endif
+
+if(var2)
+  exe = executable('breakbreakbreak', 'crashing.c')
+endif
+
+add_test('iftest', exe)

test cases/17 if/prog.c

@@ -0,0 +1 @@
+int main(int argc, char **argv) { return 0; }