static ast.Node _ExpandMacros(ast.Node node)
{
if (!(node is ast.CallExpression))
{
return(node);
}
ast.CallExpression callExpression = (ast.CallExpression)node;
Object.Macro macro = isMacroCall(callExpression, _env);
if (macro == null)
{
return(node);
}
List <Object.Quote> args = quoteArgs(callExpression);
Object.Environment evalEnv = extendMacroEnv(macro, args);
Object.Object evaluated = evaluator.Eval(macro.Body, evalEnv);
if (!(evaluated is Object.Quote))
{
System.Console.WriteLine("we only support returning AST-nodes from macros");
System.Environment.Exit(-1);
}
Object.Quote quote = (Object.Quote)evaluated;
return(quote.Node);
}
static Object.Environment extendMacroEnv(Object.Macro macro, List <Object.Quote> args)
{
Object.Environment extended = Object.Environment.NewEnclosedEnvironment(macro.Env);
int paramIdx = 0;
foreach (ast.Identifier param in macro.Parameters)
{
extended.Set(param.Value, args[paramIdx++]);
}
return(extended);
}
static void addMacro(ast.Statement stmt, Object.Environment env)
{
ast.LetStatement letStatement = (ast.LetStatement)stmt;
ast.MacroLiteral macroLiteral = (ast.MacroLiteral)letStatement.Value;
Object.Macro macro = new Object.Macro
{
Parameters = macroLiteral.Parameters,
Env = env,
Body = macroLiteral.Body
};
env.Set(letStatement.Name.Value, macro);
}
static Object.Macro isMacroCall(ast.CallExpression exp, Object.Environment env)
{
if (!(exp.Function is ast.Identifier))
{
return(null);
}
ast.Identifier identifier = (ast.Identifier)exp.Function;
Object.Object obj = env.Get(identifier.Value);
if (obj == null)
{
return(null);
}
if (!(obj is Object.Macro))
{
return(null);
}
Object.Macro macro = (Object.Macro)obj;
return(macro);
}