[fpc-pascal] a few trivial questions

Graeme Geldenhuys graemeg.lists at gmail.com
Wed May 12 17:19:57 CEST 2010

2010/5/12 spir ☣:
> * TFPList
> Is there another way to traverse a list than
>    for i :=0 to (list.count - 1) do ...
> What about list.high?

Yes, I use the Iterator design pattern. This allows me to write code as follows:

  itr: ITBStringIterator;
  itr := gIteratorFactory.StringIterator(sl);
  while itr.HasNext do

I have created Iterators for all existing list types and the code (and
accompanied article explaining Iterators) are freely available at:

Iterators have the added flexibility that I can even combine them with
regular expressions to creating a filtered list.
fitr := gIteratorFactory.FilteredStringIterator(MyStringsCollection, 'foob.*r');
while fitr.HasNext do

I can also move backwards, forwards, peak back or forward, reverse the
iterating, reset the iteration etc. Iterators are very flexible.

> Ok, I can write these funcs (I did ;-). But how comes there are no builtin functions for that?

IntToStr(), Format(), FormatFloat() etc...?

> Is there another way to slice a string than using copy. In particuliar, the count argument is not always practical to indicate the end_of_section position. (count = last-first+1)

Again here you can use iterators to iterator character by character if
you want. No need to know about Count or Count-1 etc. For all types of
lists you now have the same interface....

...Michael answered the rest of the questions.

  - Graeme -

fpGUI - a cross-platform Free Pascal GUI toolkit

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