[CLOSED] IF ... ELSE vs  IF
lazarus / 77-Embedded

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julkas · 2019-10-22 15:59

I have some functions in the following form
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i ...If
funa(x) thenbegin...Result := true;endelseResult := false; Maybe it
would be better rewrite them as
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i ...Result
:= false;If funa(x) thenbegin...Result := true;end; Pros and cons?
Keep in mind my target is embedded.

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howardpc · 2019-10-22 16:11

If you write it thus:Code: Pascal  [Select][+][-]window.onload =
function(){var x1 = document.getElementById("main_content_section");
if (x1) { var x = document.getElementsByClassName("geshi");for (var i
= 0; i case funa(x) of  True:     begin      ....      Result :=
True;    end;  False: Result := False;end;you avoid a potential double
assignment to Result (in your second proposal) of first False and then
True.

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Handoko · 2019-10-22 16:13

I usually set the default value for Result at the very beginning of
the function. So I prefer:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
Calculate(x: SomeType): Boolean;begin  Result := False;  If x
is_not_valid then Exit;   // ...  if funa(x) then  begin    // ...   
If something_bad then Exit;    Result := True;  end; end;

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440bx · 2019-10-22 16:29

Quote from: howardpc on October 22, 2019, 06:11:59 pmIf you write it
thus:Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i case
funa(x) of  True:     begin      ....      Result := True;    end; 
False: Result := False;end;you avoid a potential double assignment to
Result (in your second proposal) of first False and then True.
That is true but, in more complex logic the assignment to "result"
depends on guaranteeing that one of the paths will be taken, an
undesirable characteristic in the code.

Initializing/presetting the value of "result" guarantees that the
value of "result" will not just be some random value in some
potentially rare cases.  Such conditions/bugs are often very difficult
to pin down.

The OP's second option is solid, the first is inherently prone to
cause problems as new conditions are added.

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lucamar · 2019-10-22 17:00

You could also combine the call to the function with the assignmet to
Result:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i ...Result
:= funa(x);If Result then begin DoSomething;end;...
That makes it a direct "variable" comparison rather than a slightly
less direct comparison with a function result and ensures: 1) that
Result is always set and 2) it's set just once.

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julkas · 2019-10-23 08:05

Thanks all for replies.
After reading your posts and articles about embedded programming best
practices, I think that IF without ELSE would be better approach.
I will check ASM generated code for AVR.

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Thaddy · 2019-10-23 09:00

Quote from: julkas on October 23, 2019, 10:05:04 amThanks all for
replies.
After reading your posts and articles about embedded programming best
practices, I think that IF without ELSE would be better approach.
That is simply not true. A jump can save you. Indeed, check the
assembler.
If and if.. else have completely different meaning. Just in case you
did not understand it...