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From: hwe@beta.UUCP (Skip Egdorf)
Newsgroups: comp.lang.c
Subject: Re: Question on structures
Message-ID: <11782@beta.UUCP>
Date: Sun, 1-Nov-87 17:16:48 EST
Article-I.D.: beta.11782
Posted: Sun Nov  1 17:16:48 1987
Date-Received: Thu, 5-Nov-87 21:08:32 EST
References: <1025@phoenix.Princeton.EDU>
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 57
Keywords: Structures records
Summary: pascal 'with' in C

In article <1025@phoenix.Princeton.EDU>, asjoshi@phoenix.Princeton.EDU (Amit S. Joshi) writes:
> Hi,
> 
> I have a question on structures. It is as follows:
> 
> I have gotten really tired of typing things like a.b.c.d etc  to refer to
> elements of a structure. I remember that pascal provided me with a 'with'
> construction which allowed me to say something like 
>     "with a.b.c {now refering to d really means use a.b.c.d } ..."
> I was wondering if there is some similar contruct in C. I might be missing 
> something obvious, I wonder if somebody could help me ?. I know I could of
> course make a local copy in the program of every variable in the structures
> and then use the local copy but that seems inefficient and would be quite
> unclear.
> -- 
> Amit Joshi         |  BITNET :  Q3696@PUCC.BITNET
>                    |  USENET :  ...seismo!princeton!phoenix!asjoshi

This question arises around here once in a while, and this is how I answer,
for what it is worth.

No, there is no equivalent to 'with' in C.
However, your question is symptomatic of a deeper problem; You seem to
be trying to write Pascal programs in C. Every language has a 'style'
that encourages good programs in some way. Many programmers have seen
Fortran programs written in PL/I that are awfull (structured control
constructs not used, etc.). Lisp programmers have all seen at least
one Fortran program written with lots of parens.
 (setq ...)
 (setq ...)
 (setq ...)
 (setq ...)
 (write ...)

The point is that attempting to use one language's style with a different
language usually produces a poor product. Pascal forces one into a style
with all variables, types, and consts global at the highest level. Some
block structure can be used, but many things must be global. This leads
to a record being defined at a high level, and used with 'dot' notation
throughout the entire program. This leads to 'a.b.c.d' references and the
'with' construct to cut down on the verbage.

In C, it is much more common for the particular piece of the record (now
a struct) being processed by some sub procedure, with the sub structure
('d' in a.b.c.d) being passed as an address. This leads to a style of
several small routines dealing with 'struct a-b-c' pointers, and most
references of the form 'p->d'.

Neither of these styles is gospel, to be found everywhere always. The
programmer, as always, is responsable for picking the best tool for
the job at hand. However, the C style of dealing with deep structure
references will usually fit best within C programs, and 'with' usage will
fit best in most Pascal programs. Trying to use either in the wrong
place will usually result in a clumsy construct in the program.

					Skip Egdorf
					hwe@lanl.gov