add method
Implementation
LexoDecimal add(LexoDecimal other) {
var tmag = mag;
var tsig = sig;
var omag = other.mag;
num osig;
for (osig = other.sig; tsig < osig; ++tsig) {
tmag = tmag.shiftLeft();
}
while (tsig > osig) {
omag = omag.shiftLeft();
++osig;
}
return LexoDecimal.make(tmag.add(omag), tsig);
}