package luan.impl;

import luan.Luan;
import luan.LuanFunction;
import luan.LuanException;
import luan.LuanTable;


// unary minus
final class UnmExpr extends UnaryOpExpr {

	UnmExpr(Expr op) {
		super(op);
	}

	@Override public Object eval(LuanStateImpl luan) throws LuanException {
		Object o = op.eval(luan);
		if( o instanceof Number )
			return -((Number)o).doubleValue();
		if( o instanceof LuanTable ) {
			LuanFunction fn = Luan.getHandlerFunction("__unm",(LuanTable)o);
			if( fn != null ) {
				return Luan.first(fn.call(luan,new Object[]{o}));
			}
		}
		throw new LuanException("attempt to perform arithmetic on a "+Luan.type(o)+" value");
	}
}