/**
* Applies a mapping to a BitSet.
*
* <p>If the mapping does not affect the bit set, returns the original. Never changes the
* original.
*
* @param mapping Mapping
* @param bitSet Bit set
* @return Bit set with mapping applied
*/
public static BitSet apply(Mapping mapping, BitSet bitSet) {
final BitSet newBitSet = new BitSet();
for (int source : BitSets.toIter(bitSet)) {
final int target = mapping.getTarget(source);
newBitSet.set(target);
}
if (newBitSet.equals(bitSet)) {
return bitSet;
}
return newBitSet;
}
/**
* Divides one mapping by another.
*
* <p>{@code divide(A, B)} returns a mapping C such that B . C (the mapping B followed by the
* mapping C) is equivalent to A.
*
* @param mapping1 First mapping
* @param mapping2 Second mapping
* @return Mapping mapping3 such that mapping1 = mapping2 . mapping3
*/
public static Mapping divide(Mapping mapping1, Mapping mapping2) {
if (mapping1.getSourceCount() != mapping2.getSourceCount()) {
throw new IllegalArgumentException();
}
Mapping remaining =
create(
MappingType.INVERSE_SURJECTION, mapping2.getTargetCount(), mapping1.getTargetCount());
for (int target = 0; target < mapping1.getTargetCount(); ++target) {
int source = mapping1.getSourceOpt(target);
if (source >= 0) {
int x = mapping2.getTarget(source);
remaining.set(x, target);
}
}
return remaining;
}
/**
* Multiplies one mapping by another.
*
* <p>{@code divide(A, B)} returns a mapping C such that B . C (the mapping B followed by the
* mapping C) is equivalent to A.
*
* @param mapping1 First mapping
* @param mapping2 Second mapping
* @return Mapping mapping3 such that mapping1 = mapping2 . mapping3
*/
public static Mapping multiply(Mapping mapping1, Mapping mapping2) {
if (mapping1.getTargetCount() != mapping2.getSourceCount()) {
throw new IllegalArgumentException();
}
Mapping product =
create(
MappingType.INVERSE_SURJECTION, mapping1.getSourceCount(), mapping2.getTargetCount());
for (int source = 0; source < mapping1.getSourceCount(); ++source) {
int x = mapping1.getTargetOpt(source);
if (x >= 0) {
int target = mapping2.getTarget(x);
product.set(source, target);
}
}
return product;
}
public int getSource(int target) {
return parent.getTarget(target);
}
