With Delphi are you more likely to re-use temporary variables than with other languages?

Question

Since Delphi makes you go all the way up to the var section of a method to declare a local variable, do you find yourself breaking "Curly's Law" (re-using variables) more often than you did in college?(unless of course, you programmed Pascal in college).

If so, what do you do to break yourself of that habit, especially in functions where you need to get and/or set large numbers of properties. Is there a threshold where it is acceptable to declare TempInt : Integer and TempStr : String. (Do you use an 'e' in Temp sometimes and not other times?)

Answer 1

Not really. As I make my methods really small the var section is not far away. As my method size has reduced a lot since university, I'd say I break it less often.

Answer 2

I think delphi makes the exception with the overuse of temp variables. Most of the time when i'm creating a function/procedure where i know i will need loops or temp strings, first thing i do is to create a var i,j:integer; tmp:string; and add more as needed :)

Answer 3

Declaring variables is very simple - some times they would get automatically created ('for' loop template), other times you can just use 'Declare Variable' refactoring (or 'Add Local Var' if you are using MMX - as you should).

Answer 4

I probably would have found this to be a bigger problem if hadn't had CTRL-SHIFT-V as a shortcut to the VAR section. I'm not writing GIGANTIC methods here, but sometimes they get a little out of hand (and I can justify this of course) and it helps a lot. I'm not sure if that shortcut comes from cnTools or GExperts, but they're both pretty useful and I'd recommend them both.

Answer 5

I don't tend to reuse local vars as a general safety rule. I do love the new "var" live template stuff in d2007+. Just type var[tab] and the helper pops up. Also check out Ctrl-Shift-D (others mentioned Ctrl-Shift-V for local vars) to declare a field.

Answer 6

This is just a matter of discipline. Yes, Delphi would probably be better served by inline variable declaration, but that's not really a big deal. Just be sure to name your variables in a descriptive way, and then it will just feel awkward to use them incorrectly. And, as Stephan Eggermont said, if your methods are really getting that long, then that's a whole different code smell.

Answer 7

I definitely do tend to re-use local variables like 'Findex' (or just plain 'i') if the routine has several distinct iterative sections to it. Not really the best practice I guess, but I'd like to think it's only really obvious where I do it, and obviously the usage doesn't overlap.

It's not usually a big deal to go back to the top of the routine and key-in the new variables, though I didn't know about Ctrl-Shift-V (will be trying that later!).

It'll be interesting to see what everyone else says. :-)

Answer 8

As a long time Delphi user (since 1.0) this is the major thing I hate about Pascal. all other modern languages support definition at the point of use, yet Delphi persists with the var section, and Delphi programmers persist in ridiculous hand-waving antics to justify it.

Answer 9

I hardly ever reuse variables. I hate to say never, but it is close to never.

Here is why:

• Small methods (It's good practice to keep methods and property-getters/setters as concise as possible).
  • When only one thing is done, no need to reuse variables
  • The var section is always on the screen.
• The compiler reuses the storage as necessary, so reuse is only a lazy coder crutch with no performance improvements.
• Newer versions of Delphi have CTRL+SHIFT+V to declare a variable if I am feeling lazy.
• Reusing variables makes debugging more difficult - more time and effort is spent on maintenance then development (for any serious application) so always do things to make maintenance easier, even if it makes development a little harder.
• Prefer user defined types, so a Account Balance is a specific type, not just a Currency. This means variables are less reusable anyway.
• For loop variables (a common reused variable) are used less now that we can use for in and skip the iterator all together.
• My variables have descriptive names, so it would not make sense to use them out of context.

Generally speaking, I like having all the variables at the top for the same reason I like having an interface section on my units. It is kind of like having an abstract on a paper - give me a general idea of what is going on without having to read the whole paper. Delphi could benefit from having the ability to declare variables at "inner scope" like within a for loop or other begin / end blocks, but I don't know how much that would distract from the cleanliness and readability of Delphi code.

Answer 10

Well Curly did have a good point. I'm a sinner in that respect occasionally. Usually just a temp string variable for convenience more than anything.

To be honest I've never really thought about it... until now. I have no issue with the VAR section being where it is as that's been a habit formed since Delphi 1.0.

To answer the question, I only re-use a temp variable, usually a string, and usually only to gain some slight performance improvements. Don't have an issue with that.

Answer 11

You can develop your own style of coding that uses variables as required. I generally use unique vars (90%) with a few temp vars (10%) when required.

It depends on the nature of the var. If it is a var to help support other code (counter for loops, building SQL strings, etc.) then a temp var you can re-use is helpful. In this case your temp vars are useful as "disposable" vars in sections of code. Just add a comment to your var declarations indicating the temp vars.

i.e. //temp vars are re-used as required in this procedure --> clear/re-initialise them after/before use.

Other than that I avoid temp vars & never use them to hold critical data. A unique var should be used then to avoid confusion & make readability/maintenance of code clearer.