Re: Clever UNIX/C Constructs -- RPG400-L



On Thu, 4 Jan 2001, Evan Harris wrote:

> Hi Scott
> 
> The original thread (which I think I started) was based on the premise that:
> 
> EVAL Variable = Variable + 5
> 
> is, in my opinion at least,
> 
> much more readable and obvious than
> 
> variable += 5
> 
> So far the major argument for providing this syntax has been to save 
> typing: if there is another argument I'd be more than interested to hear it 
> as I really cannot see what it adds to any language. As per Richard's 
> comments it seems it arose from a design decision due to limitations of the 
> past - just as the columnar RPG format was rooted in its origins.

In C, I was always told that "A += 5" performs better than "A = A + 5".
The reason being that the compiled code only needs to load the value of A
from memory once instead of twice.  

My opinion is that there are circumstances when the "A +=" operator is
more intuitive for the person reading the code than the "A = A + " would
be.  Since this is a question of style, and style is purely a matter of
opinion, you don't necessarily have to agree with me.

> I agree with your statements regarding RPG syntax not necessarily being 
> obvious to the uninitiated, but it seems to me that += etc is just more of 
> the same from a different language. To make it clear where I am coming 
> from, would you want indicator logic added to C ? 

The whole premise of this is that "+=" makes for code that isn't obvious
to the reader.  I disagree with this premise.   This is NOT like putting
indicators into C.

There are C expressions that I don't like.  For example code that looks
like this:   
      newoption = (newoption == 0) ? newoption : newoption - 1;

Would be something that I would prefer not to add to RPG.  However, I just
don't see "A += 5" as being hard to follow.


> Why add something to RPG 
> that adds nothing content-wise merely additional form ?

I agree with this.  I wouldn't ask for this functionality in RPG unless I
was down to my last $2, and this was a $2 option.

> 
> Excuse my ignorance if I get this wrong (I have no more than a passing 
> acquaintance with C) but in the above example what would be the effect  of:
> 
> variable =+ 5
> 
> Would it (as I understand it) assign 5 to the variable rather than 
> incrementing it by 5 ? What are the side-effects (bad choice of words 
> possibly) of other incorrectly typed terse assignments ? And what is the 
> effect on debugging to those that are not proficient with this style of 
> expression ?

correct.   "variable =+ 5"  is the same thing as "variable = +5"

> 
> These days when I code I like to think that I am coding for "whoever comes 
> next" and that they will (hopefully) be impressed with how easy it is to 
> maintain or (god forbid) debug - not by having to refer to the manual to 
> understand indicators, cycles, expressions or whatever.
> 

The problem with RPG is we try to make the compiler writers decide what is
"good code" and what is "bad code", and then force it upon everyone.  They
don't try that in C.  They give you all the options, and leave it to the
programmer to develop code thats easy to follow.

The result, IMHO, is easier to follow C code.  The compiler developer
can't anticipate every piece of code we write, so give the programmer the
tools to do it the way that seems intuitive to him.


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