Difference between Sub-Procedure and Function

[Krishan Gopal]

Hi All,

I have one more silly question the difference between Sub-procedure and Function. One I know is that Returning Value. Are there any more differences?
Functions are faster compare to Procedures, I heard but don't know why.

Functions generally used for small business logic not for lengthy business logic.

Please give me your thought.

 

[RealHeavyDude]

Basically it's up to you to choose - whatever suits you better.

Differences OTOH:

• For a function call the parameter signature is checked at compile-time (but not when you use DYNAMIC-FUNCTION) whereas for procedures it's not.
• In functions or methods there are no input blocking statements like WAIT-FOR or PROCESS EVENTS allowed - these are only allowed in procedures.
• The RUN statement has a default search order whereas a function call requires the function to reside in the same procedure unless you use DYNAMIC-FUNCTION.

Regards, RealHeavyDude.

 

[Krishan Gopal]

Thanks a lot,

But as I read, in Sub-Procedure aslo we can't add any input blocking statement, am I right?

 

[RealHeavyDude]

Out of experience I can tell you that this is at least not true for the PROCESS EVENTS statement which will throw a run time error when issued from a function or method.

HTH, RealHeavyDude.

 

[GregTomkins]

In an attempt to think of something RHD did not ... functions are pickier than procedures, regarding type compatability. I don't know all the ins and outs of this, but here is an example:

function f returns char (p as int):
end.

f ("1"). /* this will not compile */

run p ("1"). /* this will compile and will also run cleanly, even though it passes a CHAR to an INT */

procedure p:
def input param p as i no-undo.
end.

Whether this is a good thing or not is a matter of opinion, I suppose.

 

[GregTomkins]

Oh, and after many years of screwing around with external procedures vs. internal procedures vs. functions, my opinion is, unless it is being called in a tight loop, external procedures are generally best; there are many considerations in choosing between the three, but I generally prefer external procedures because they are the simplest and guarantee isolation of variables and buffers.

 

[TomBascom]

I like functions because returning a value is so much cleaner and more elegant.

Also -- functions can live in another procedure... the definition takes IN proc-handle or IN SUPER. Works great for building and accessing code libraries.

 

[Krishan Gopal]

My sincere thanks to all for replying.

AS all we know, nothing can replace External Procedure in Progress as it's the heart of progress 4GL, unitl we go for OOPs (OpenEdge - ABL).

I was trying to clear the things only between Sub procedures and Functions.
@ Tom - Sub procedures is also the part of External procedure and we can execute those by running procedures persistently and calling that procedure IN that persistent procedure.

So may I assume that choosing between Sub - Procedures and Functions depends upon individual interest?

 

[GregTomkins]

I'm tempted to get into a debate about Super Procedures and libraries and so on... but I suppose I should do some real work. Anyway, I think what you said is a fair statement. Basically, functions vs. internal procedures is mostly a matter of style and preference. Both can be used in bad ways and both can be just fine.