Re: Clause "with and use"

[Marin David Condic <nobody@noplace.com>]

I tend to like a use clause for things similar to dispatching on a 
tagged record. Dispatching would be a joke if you *always* had to 
specify which package you wanted to reference, right? So there must be 
something "good" about the "use" clause.

If I had some sort of "display (float)" and a "display (integer)" I'd 
like to just say "Display (Object)" and the compiler sorts it out. The 
"use" clause seems to be useful where you want something to appear as a 
primitive/intrinsic operation of some kind. At other times, I want to 
make it clear that I am referencing something external to the local 
context - lack of "use" makes that clear. I don't know that I could 
formulate a hard-and-fast rule as to when it is good and when it is bad, 
but I think the language designers had something similar to this in mind 
when creating it: "Sometimes you want it to look 'intrinsic' and other 
times you want it explicit that something is external. Hence we added 
the 'use' when the 'with' alone is really all that is needed."

MDC


Robert I. Eachus wrote:
> 
> It can, but it doesn't always.  A good example is a group of ADTs that 
> have display operations.   The display operations belong in the package 
> with the other operations on the same type, but they may be the only 
> operation that needs to use Text_IO or some graphics packages.
> 
> You can organize things using child packages to segregate the I/O 
> operations, but you end up with the display operation being the only one 
> to use the child package.
> 
> Instead I usually end up with a generic package that handles the display 
> operations in a data independent manner, and the individual display 
> operations instantiate that package.  Now the use clause is for a local 
> generic instance, but it is still there.
> 


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Marin David Condic
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