/**
* 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 getSourceOpt(int target) {
return parent.getTargetOpt(target);
}