public IObject Eval(INode node, Enviroment enviroment)
{
switch (node)
{
// 文
case Root root:
return(this.EvalRootProgram(root.Statements, enviroment));
case ExpressionStatement statement:
return(this.Eval(statement.Expression, enviroment));
case BlockStatement blockStatement:
return(this.EvalBlockStatement(blockStatement, enviroment));
case ReturnStatement returnStatement:
var value = this.Eval(returnStatement.ReturnValue, enviroment);
if (this.IsError(value))
{
return(value);
}
return(new ReturnValue(value));
case LetStatement letStatement:
var letValue = this.Eval(letStatement.Value, enviroment);
if (this.IsError(letValue))
{
return(letValue);
}
enviroment.Set(letStatement.Name.Value, letValue);
break;
// 式
case PrefixExpression prefixExpression:
var right = this.Eval(prefixExpression.Right, enviroment);
if (this.IsError(right))
{
return(right);
}
return(this.EvalPrefixExpression(prefixExpression.Operator, right, enviroment));
case InfixExpression infixExpression:
var ifLeft = this.Eval(infixExpression.Left, enviroment);
if (this.IsError(ifLeft))
{
return(ifLeft);
}
var ifRight = this.Eval(infixExpression.Right, enviroment);
if (this.IsError(ifRight))
{
return(ifRight);
}
return(this.EvalInfixExpression(
infixExpression.Operator,
ifLeft,
ifRight,
enviroment
));
case IfExpression ifExpression:
return(this.EvalIfExpression(ifExpression, enviroment));
case IntegerLiteral integerLiteral:
return(new IntegerObject(integerLiteral.Value));
case BooleanLiteral booleanLiteral:
return(this.ToBooleanObject(booleanLiteral.Value));
case Identifier identifier:
return(this.EvalIdentifier(identifier, enviroment));
case FunctionLiteral functionLiteral:
return(new FunctionObject()
{
Parameters = functionLiteral.Parameters,
Body = functionLiteral.Body,
Enviroment = enviroment,
});
case CallExpression callExpression:
var fn = this.Eval(callExpression.Function, enviroment);
if (this.IsError(fn))
{
return(fn);
}
var args = this.EvalExpressions(callExpression.Arguments, enviroment);
if (this.IsError(args.FirstOrDefault()))
{
return(args.First());
}
return(this.ApplyFunction(fn, args));
}
return(null);
}
