Constants: Do they have any advantage over variables?

[TheDcoder]

I just thought of this... Do Constants and Variables have any differences other than Constants cannot be changed? I know that Python does not have such things like Constants... But is there a difference between them? any advantages when using Constants whenever we can?

The uses of Constants which I have discovered so far are:

1. Coding practices (You know what things are not supposed to be changed while the program is running).
2. Preventing code from modifying their value.

So, is there anything more than what meets the eye? I think the developers of AutoIt can answer this question.

Edited June 2, 2016 by TheDcoder
Minor Sentence Edit

[mLipok]

  On 6/2/2016 at 2:22 PM, TheDcoder said:

• Coding practices (You know what things are not supposed to be changed while the program is running).
• Coding practices - Magic Number prevention + readability
• Creating a more agile code, easy to change management/development concept.
• Preventing code from modifying their value.

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just my 2c

[TheDcoder]

@mLipok I forgot those 2 , Thanks for mentioning them .

[JohnOne]

Those 2 are no different than variables.

[TheDcoder]

oh, yeah

[RTFC]

A smart compiler can optimise memory storage better if it knows in advance that a particular subset of variables will not ever be resized. This can reduce fragmentation of virtual memory.

[mLipok]

@RTFC I'ts interesting.
 

[mLipok]

  On 6/3/2016 at 7:41 AM, JohnOne said:

Those 2 are no different than variables.

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Yes but 2 can be used secure only with 4.

 

[TheDcoder]

  On 6/3/2016 at 8:39 AM, RTFC said:

A smart compiler can optimise memory storage better if it knows in advance that a particular subset of variables will not ever be resized. This can reduce fragmentation of virtual memory.

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I know that those compilers convert the code to native machine code.... I know that our aut2exe does not do that . But AutoIt3Wrapper made by @Jos has an option to replace constants with their actual value... That might be somewhat of an advantage but its very useless if that constant is not hard coded in the script! (Like Control IDs of Controls in a GUI).

  On 6/3/2016 at 8:48 AM, mLipok said:

Yes but 2 can be used secure only with 4.

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I don't get what you are trying to say .

[guinness]

Yeah, Jos based the idea on PreExpand.

[TheDcoder]

@guinness Do you have access to AutoIt's code? If yes, how does AutoIt handle constants?

[czardas]

From my perspective there are two types of constant: artificial constants and real constants. Real constants are things like Pi, and artificial constants are based on design choices - for example magic numbers by Microsoft. @RTFC makes a good point which I hadn't considered. Although it appears to make sense. I'm not sure if this is the case with AutoIt. It may well be that using the Const keyword actually slows down the script by a very tiny amount, although you would hardly notice any difference. Hard coded values will probably always have a slight edge over variables, which is why @guinness created PreExpand. You should always use the Const keyword for constants. It's good style and prevents corruption.

Edited June 4, 2016 by czardas

[TheDcoder]

  On 6/4/2016 at 10:14 AM, czardas said:

It may well be that using the Const keyword actually slows down the script by a very tiny amount, although you would hardly notice any difference.

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Its the same case when we declare a variable too I think.

[czardas]

  On 6/4/2016 at 1:15 PM, TheDcoder said:

Its the same case when we declare a variable too I think.

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That's what I said.

  On 6/4/2016 at 10:14 AM, czardas said:

Hard coded values will probably always have a slight edge over variables

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[TheDcoder]

oh, ok, silly me

[guinness]

  On 6/4/2016 at 5:42 AM, TheDcoder said:

@guinness Do you have access to AutoIt's code? If yes, how does AutoIt handle constants?

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Yes, though I haven't really looked in that code if I am honest.

[TheDcoder]

Oh

[guinness]

  On 6/5/2016 at 4:03 AM, TheDcoder said:

Oh

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Even if I did, I don't know how much I can divulge about the internals.

[iamtheky]

  Quote

Hard coded values will probably always have a slight edge over variables

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  Quote

It may well be that using the Const keyword actually slows down the script by a very tiny amount

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So, in conclusion, magic numbers save milliseconds.

[guinness]

Seems this is all speculation right now. I prefer benchmarking over rumours.