/// <summary>
/// expression ::=
/// operand '=' expression
/// operand '+' expression
/// operand '-' expression
/// operand '*' expression
/// operand
/// </summary>
/// <exception cref="DynException"></exception>
public DynAstNodeExpression MatchExpression()
{
var r = new DynAstNodeExpression();
r.Left = MatchOperand();
var lexeme = PeekLexeme();
switch (lexeme.Token)
{
case DynToken.SymbolPlus:
case DynToken.SymbolMinus:
case DynToken.SymbolStar:
case DynToken.SymbolEqual:
NextLexeme();
r.Operation = lexeme;
r.Right = MatchExpression();
break;
}
return(r);
}
/// <summary>
///
/// </summary>
/// <param name="e"></param>
/// <param name="ilg"></param>
/// <param name="scope"></param>
/// <param name="args"></param>
/// <exception cref="DynException"></exception>
public void EmitExpression(DynAstNodeExpression e, ILGenerator ilg, Dictionary <string, LocalBuilder> scope, Dictionary <string, int> args)
{
if (e.Operation is null)
{
EmitOperand(e.Left, ilg, scope, args);
return;
}
switch (e.Operation.Token)
{
case DynToken.SymbolEqual:
{
if (e.Left.Lexeme.Token != DynToken.Identifier)
{
throw new DynException($"语法错误，赋值操作只可作用于左值。");
}
// Right
EmitExpression(e.Right, ilg, scope, args);
if (GlobalVariables.Contains(e.Left.Lexeme.Identifier))
{
ilg.Emit(OpCodes.Stfld, e.Left.Lexeme.Identifier);
break;
}
if (!scope.ContainsKey(e.Left.Lexeme.Identifier))
{
LocalBuilder lbt = ilg.DeclareLocal(anyType);
scope.Add(e.Left.Lexeme.Identifier, lbt);
}
LocalBuilder lb = scope[e.Left.Lexeme.Identifier];
ilg.Emit(OpCodes.Stloc, lb.LocalIndex);
break;
}
case DynToken.SymbolPlus:
{
// Left
EmitOperand(e.Left, ilg, scope, args);
// Right
EmitExpression(e.Right, ilg, scope, args);
//ilg.Emit(OpCodes.Add);
ilg.Emit(OpCodes.Call, anyType.GetMethod("add_operator"));
break;
}
case DynToken.SymbolMinus:
{
// Left
EmitOperand(e.Left, ilg, scope, args);
// Right
EmitExpression(e.Right, ilg, scope, args);
ilg.Emit(OpCodes.Sub);
break;
}
case DynToken.SymbolStar:
{
// Left
EmitOperand(e.Left, ilg, scope, args);
// Right
EmitExpression(e.Right, ilg, scope, args);
ilg.Emit(OpCodes.Mul);
break;
}
default:
throw new DynException($"语法错误，未知的表达式 {e.Operation}");
}
}
