5.3 C++-style Iteration

C++ iteration is designed to more closely mimic iterator loops as written in C++ OEChem (to aid in porting) but it also provides a much more rich interface, including things like the ability to iterate backwards as well as forwards.

Methods that support this style include:

Method	Java	C++
Creation	OEAtomBaseIter i;	OEIter<OEAtomBase> i;
Increment	i.Increment()	i;
Decrement	i.Decrement()	i;
Increment by n	i.Increment(n)	i += n;
Decrement by n	i.Decrement(n)	i -= n;
Go to first	i.ToFirst();	i.ToFirst()
Go to last	i.ToLast();	i.ToLast()
De-reference (access the object)	i.Target()	operator ->
pointed to, i.e. OEAtomBase)
Validity	i.IsValid()	operator bool

To loop forward over the atoms of a molecule:

for (OEAtomBaseIter aiter=mol.GetAtoms();aiter.IsValid();aiter.Increment()) {
  OEAtomBase atom = aiter.Target();
  System.out.println(atom.GetAtomicNum());
}

or without the temporary OEAtomBase object:

for (OEAtomBaseIter aiter=mol.GetAtoms();aiter.IsValid();aiter.Increment()) {
  System.out.println(aiter.Target().GetAtomicNum());
}

Iterating backwards over the atoms is just as easy. This next listing also shows how iterators can be re-used.

OEAtomBaseIter aiter = mol.GetAtoms();

// C++ style for loop, backwards over atoms
for (aiter.ToLast();aiter.IsValid();aiter.Decrement()) {
  System.out.println(aiter.Target().GetAtomicNum());
}

// move iterator back to end and loop backward with C++ style while loop
aiter.ToLast();
while(aiter.IsValid()) {
  System.out.println(aiter.Target().GetAtomicNum());
  aiter.Decrement();
}

				OEChem - Java Theory Manual

				OEChem - Java Theory Manual