private static EvalValue CalcIf(IEnvironment env, AstIf ast)
{
// 返回值为执行的最后一条语句或表达式的值
var ret = new EvalValue();
var cond = ast.condition.Eval(env);
if (cond.type == EvalValueType.STRING)
{
throw new RunTimeException("条件表达式不能为字符串", ast.condition);
}
else if (cond.type == EvalValueType.INT && cond.intVal > 0)
{
foreach (var item in ast)
{
ret = item.Eval(env);
}
}
else if (ast.elseBlock != null)
{
// 有else块
foreach (var item in ast.elseBlock)
{
ret = item.Eval(env);
}
}
return(ret);
}
AstIf ProcessIfStatement(AstIf astIf)
{
var safeLastIfAlternative = _lastIfAlternative;
_lastIfAlternative = astIf.Alternative;
Descend();
_lastIfAlternative = safeLastIfAlternative;
IsAfterJump = false;
return(astIf);
}
static AstNode RemoveUnreachableCode(AstIf ifStatement, bool inList)
{
var conditionValue = ifStatement.Condition.ConstValue();
if (conditionValue == null)
{
return(ifStatement);
}
AstStatement?statement;
AstStatement?falsyStatement;
if (TypeConverter.ToBoolean(conditionValue))
{
statement = ifStatement.Body;
falsyStatement = ifStatement.Alternative;
}
else
{
statement = ifStatement.Alternative;
falsyStatement = ifStatement.Body;
}
AstVar?declarations = null;
if (falsyStatement != null)
{
declarations = GetDeclarations(falsyStatement);
}
switch (statement)
{
case null:
return(declarations ?? Remove);
default:
if (declarations == null)
{
return(statement);
}
var statements = new StructList <AstNode>();
statements.Add(declarations);
statements.Add(statement);
return(inList
? SpreadStructList(ref statements)
: new AstBlock(ifStatement)
{
Body = statements
});
}
}
/// <summary>
/// 解析语句state
/// </summary>
/// <returns></returns>
private AstStatement DoStatement()
{
// state ::== <while><expr><do>{<expr>|<state>}<end>';'
// | <if><expr><do>{<expr>|<state>}<end>';'
// | <return><expr>';'
if (Is("while", TokenType.KEYWORD))
{
// while语句
Pass("while", TokenType.KEYWORD);
AstExpression condition = DoExpression();
Pass("do", TokenType.KEYWORD);
List <AstNode> list = DoBlock();
Pass("end", TokenType.KEYWORD);
Pass(";", TokenType.SEPERATOR);
var ret = new AstWhile(list, condition);
Utils.LogDebug("[P] while语句: {0}", ret.ToString());
return(ret);
}
if (Is("if", TokenType.KEYWORD))
{
// if语句
Pass("if", TokenType.KEYWORD);
AstExpression condition = DoExpression();
Pass("do", TokenType.KEYWORD);
List <AstNode> list = DoBlock();
List <AstNode> elseList = null;
if (Is("else", TokenType.KEYWORD))
{
// 有else块
Pass("else", TokenType.KEYWORD);
elseList = DoBlock();
}
Pass("end", TokenType.KEYWORD);
Pass(";", TokenType.SEPERATOR);
var ret = new AstIf(list, condition, elseList);
Utils.LogDebug("[P] if语句: {0}", ret.ToString());
return(ret);
}
if (Is("return", TokenType.KEYWORD))
{
// return语句
Pass("return", TokenType.KEYWORD);
AstExpression expr = DoExpression();
var ret = new AstReturn(new List <AstNode>(), expr);
Utils.LogDebug("[P] return语句: {0}", ret.ToString());
return(ret);
}
throw new ParseException(m_scanner.Peek(0), "未知语句");
}
private void CompileIf(AstIf node, Syt syt, StringBuilder sb)
{
var lblTrue = Id("IF_TRUE");
var lblEndif = Id("IF_END");
CompileRecursive(node.exprCond, syt, sb);
sb.AppendLine("if-goto " + lblTrue);
if (node.rgstmElse != null)
CompileRecursive(node.rgstmElse, syt, sb);
sb.AppendLine("goto " + lblEndif);
sb.AppendLine("label " + lblTrue);
CompileRecursive(node.rgstm, syt, sb);
sb.AppendLine("label " + lblEndif);
}
