subtract method
Implementation
LexoDecimal subtract(LexoDecimal other) {
var thisMag = mag;
var thisSig = sig;
var otherMag = other.mag;
num otherSig;
for (otherSig = other.sig; thisSig < otherSig; ++thisSig) {
thisMag = thisMag.shiftLeft();
}
while (thisSig > otherSig) {
otherMag = otherMag.shiftLeft();
++otherSig;
}
return LexoDecimal.make(thisMag.subtract(otherMag), thisSig);
}