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| Components: Miscellaneous: Miscellaneous |
| Name: Iterators |
Date: 10/21/03 8:05:00 PM |
Environment:
Delphi 1.0, Delphi 3.0, Delphi 5.0, Delphi 7.0, Kylix 2, Windows 2000, Windows 95, Windows NT, Windows XP, Delphi 2.0, Delphi 4.0, Delphi 6.0, Kylix 1, Kylix 3, Windows 3.1, Windows 98, Windows NT 4.0 |
Download |
| Type: Freeware with Source |
Size: 7715 |
Price:
Source: |
Online Registration: Link Not Available |
Description:
Motivation:
Delegation of extensive loop constructions as one procedure call. One should not be forced to repeat them again and again.
The traditional way (e.g. C++ STL) uses an object with up to 6 methods (create, init, eof, value, step, free); in contrast to this with CLU-iterators you cannot run two iterators simultaneously (in one thread) to e.g. compare two lists but it is much easier, and by the way no space on the heap is necessary.
By the way: In qgrids.pas the method TSparsePointerArray.ForAll and in TVision's TCollection.ForEach and TCollection.FirstThat such iterators were already simulated...
Application:
Loop through containers (lists, trees, parameters, directories, registry, etc.). "frame routines", e.g. for locking purposes.
Semantic:
Principely the iterator is called, which on its part calls the loop body on each yield.
The loop body and its scope (principly a local procedure) are transferred as hidden parameters.The iterator communicates with the loop body via reference parameters.
Simple example (result: '1 2 3 4 7 8 9 10 ')
type
tn_set=byte;
tsn_set=set of tn_set;
iterator for_in(var i:byte; const s:tsn_set);
var
j: tn_set;
ss: tsn_set;
begin
ss:=s; (* Local copy, might be necessary or implicitely supplied *)
for j:=0 to 255 do begin
if j in ss then begin
i:=j;
YIELD(iterator_base);
end;
end;
end;
var
q: tn_set;
begin
for_in(q, [1..3, 7..10]) do begin
write(q,' ');
end;
end.
References:
http://www.home.unix-ag.org/tjabo/ruby/uguide/uguide08.html
http://webster.cs.ucr.edu/Page_asm/ArtofAssembly/ch12/CH12-6.html
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Additional Information:
- Total downloads between 10/22/03 and 7/6/08: 467
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| Author: Jasper Neumann |
No Homepage Specified |
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