clone method
Implementation
MPData clone(){
if( _val.isEmpty ){
// ゼロ値
MPData a = MPData( 2 );
a.set( 0, MultiPrec.lenCoef );
a.set( 1, 0 );
return a;
}
MPData a = MPData( _val.length );
for( int i = 0; i < _val.length; i++ ){
a._val[i] = _val[i];
}
return a;
}