public static async Task <LuaObject> BinaryOperationAsync(Engine engine, BinaryOp op, LuaObject left,
LuaObject right, CancellationToken token = default)
{
// Metatables
var metaKey = op.ToMetaKey();
var isDifferent = op == BinaryOp.Different;
if (isDifferent)
{
metaKey = BinaryOp.Equal.ToMetaKey();
}
if (!string.IsNullOrEmpty(metaKey) || isDifferent)
{
var meta = left.GetMetaMethod(engine, metaKey);
if (meta.IsNil())
{
meta = right.GetMetaMethod(engine, metaKey);
}
if (!meta.IsNil())
{
var result = await meta.CallAsync(engine, Lua.Args(left, right), token).FirstAsync();
if (isDifferent)
{
result = !result.AsBool();
}
return(result);
}
}
// Default implementations
double leftDbl, rightDbl;
switch (op)
{
// String
case BinaryOp.Concat:
return(left.AsString() + right.AsString());
// Logic
case BinaryOp.And:
return(left.AsBool() ? right : left);
case BinaryOp.Or:
return(left.AsBool() ? left : right);
// Relational
case BinaryOp.Equal:
return(left.Equals(right));
case BinaryOp.Different:
return(!left.Equals(right));
case BinaryOp.LessThan:
case BinaryOp.LessOrEqual:
case BinaryOp.GreaterThan:
case BinaryOp.GreaterOrEqual:
if (left.IsString() && right.IsString())
{
leftDbl = StringComparer.Ordinal.Compare(left.AsString(), right.AsString());
rightDbl = 0;
}
else if (left.IsNumber() && right.IsNumber())
{
leftDbl = left.AsNumber();
rightDbl = right.AsNumber();
}
else
{
throw new LuaException($"attempt to compare {right.Type.ToLuaName()} with {left.Type.ToLuaName()}");
}
break;
// Arithmetic
case BinaryOp.Addition:
case BinaryOp.Division:
case BinaryOp.Subtraction:
case BinaryOp.Multiplication:
case BinaryOp.Power:
case BinaryOp.Modulo:
leftDbl = left.AsNumber();
rightDbl = right.AsNumber();
break;
default:
throw new ArgumentOutOfRangeException();
}
switch (op)
{
case BinaryOp.Addition:
return(FromNumber(leftDbl + rightDbl));
case BinaryOp.Division:
return(FromNumber(leftDbl / rightDbl));
case BinaryOp.Subtraction:
return(FromNumber(leftDbl - rightDbl));
case BinaryOp.Multiplication:
return(FromNumber(leftDbl * rightDbl));
case BinaryOp.Power:
return(FromNumber(Math.Pow(leftDbl, rightDbl)));
case BinaryOp.Modulo:
return(FromNumber(leftDbl % rightDbl));
case BinaryOp.LessThan:
return(leftDbl < rightDbl);
case BinaryOp.LessOrEqual:
return(leftDbl <= rightDbl);
case BinaryOp.GreaterThan:
return(leftDbl > rightDbl);
case BinaryOp.GreaterOrEqual:
return(leftDbl >= rightDbl);
default:
throw new IndexOutOfRangeException();
}
}