Something that has been boggling my mind is that I don't understand why some (most) string routines are functions that give a result and some string routines are procedures which change the original string.
S2 := Copy(S1,3,2);
Copies into S2 from S1 the 2 characters starting from the 3rd position.
Delete(S,3,2);
Deletes from S the 2 characters starting from the 3rd position.
I would have thought it more consistent to have Delete (and a few others) behave like most other string routines, so you could write:
S2 := Delete(S1,3,2);
Why isn't that the case?
The reason is in the name.
Copy is a function because it is supposed to create a copy. A procedure version of Copy would need an additional parameter, because when there is already a source, where would the target go?
Delete is a procedure because it is supposed to delete characters from a string. For a function version of Delete which returns the outcome of the delete operation, what should become of the source? You're calling a delete operation on it: it cannot remain unaltered.
As analogy; compare it with the procedure TRect.Offset and the function TRect.CenterPoint. Offset performs an operation on the entity, where CenterPoint reads a attribute of the entity.