string argument as array index

[Weiss]

I was thinking to implement a simple analogue of TDictionary, and all works remarkably well. For my needs, I get-by with a class where TPair is emulated with parallel arrays. One thing I can't emulate is placing a string as an argument in a square brackets. And with that being not done, I have to replace a syntax in many  lines of existing code. Not big of a deal, but I am curious, how is it done? Say, I have a key "myKey", how in free pascal I can do

Code: Pascal  [Select][+][-]

1. ..
2. someVariable :=myHomeMadeDictionary[myKey]
3. ..
4.  

sorry for such "insightful" question
 

[Thaddy]

I do not understand the question: generics are basically a sourcecode replay and a fill in. That is codewise not efficient, but anything else, because the compiler will generate code for every specialization, your "insightfull" part is even worse.

Generics do not loose speed. Inheritance does not loose speed, but your suggestion does loose speed.

A small example of being blind to what is really happening under the hood.

[cdbc]

Hi
It's got to do with properties...
Have a look in the attached unit, it's just a quick mockup, but you should get it...
Regards Benny

[Mr.Madguy]

I guess, this can be done via default array property. Like this one:

Code: Pascal  [Select][+][-]

1.       function GetItem (AKey:TKey):TValue;
2.       procedure SetItem(AKey:TKey;AValue:TValue);
3.       property Items[AIndex:TKey]:TValue read GetItem write SetItem;default;
4.  

[Thaddy]

Hi
It's got to do with properties...
Have a look in the attached unit, it's just a quick mockup, but you should get it...
Regards Benny

Benny, you are wrong here. Read my answer: he thinks he can speed up code that way and that is wrong.

The recent Pascal syntax is so rich it can be done but it will be slower.

[paule32]

I use TCollection

[cdbc]

Hi Thaddy
I saw that, but decided to answer the question about default props, just like Mr.Madguy...
His fiddling with this, is his business, I know exactly when and where to use generics 
Regards Benny

[marcov]

Maybe procedural properties also support [] ?

https://www.freepascal.org/docs-html/current/ref/refse27.html

[Weiss]

Hi
It's got to do with properties...
Have a look in the attached unit, it's just a quick mockup, but you should get it...
Regards Benny

great! Thank you sir

[PascalDragon]

Hi
It's got to do with properties...
Have a look in the attached unit, it's just a quick mockup, but you should get it...
Regards Benny

Benny, you are wrong here. Read my answer: he thinks he can speed up code that way and that is wrong.

Nowhere did Weiss mention anything about optimization, so the suggestions by both cdbc and Mr.Madguy are indeed the correct ones (and can also be used together with generics if necessary).

[jcmontherock]

You can also use TStringList Name Values with objects. So a lot of work is done by Pascal.

[Weiss]

TStringList was on my mind, thank you jcmontherock. And Marcov, great lead.

To the question why, as I see it gets some negative reaction, I have a lot to say. For one, code writing is my hobby, I did not slow down anybody's project or used up resources anywhere, other than family time.

I get about 40 warnings from Generics.Collections. Code compiles and works, but those warnings lead me to feeling that there is some heywiring under the hood. Maybe nothing important.

There was saying somewhere, with OOP if you want banana you are getting it with guerilla holding that banana and the whole jungle behind. I only need small portion of Generics, seemed logical to write that portion.

[jamie]

Look at the Fpg unit, it contains Generics that is much lighter than the suggested collections and from my experience actually makes the compiler happier.

[Thaddy]

Generics.Collections is Delphi compatible. FGL is not! But you are correct, it is lightweight.
Also note the confusion that always seems to exist: some think a dictionary <> map, while dictionary = map.
Fgl and generics.collections are not compatible but contain some of the same functionality.

For anything that translates from or needs Delphi: always use generics.collections.
For much of the code you only use in FreePascal? feel free to use the fgl.
I have another strong favorite, lgenerics by avk, but that is not in the standard distribution.

From a CS point of view it is best.

[jamie]

Generics.Collections is Delphi compatible. FGL is not! But you are correct, it is lightweight.
Also note the confusion that always seems to exist: some think a dictionary <> map, while dictionary = map.
Fgl and generics.collections are not compatible but contain some of the same functionality.

For anything that translates from or needs Delphi: always use generics.collections.
For much of the code you only use in FreePascal? feel free to use the fgl.
I have another strong favorite, lgenerics by avk, but that is not in the standard distribution.

From a CS point of view it is best.

That's fine and dandy however, serious use of the Delphi compatible collections generics, crashes the compiler!

On top of that, it's not well behaved like those promoting it, think.

 I will say however, it seems to work in Delphi's environment and after looking at some code snippets they are not actually the same as implemented in the
supported unit for fpc. So, who's so say where the real problem is.

Jamie