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Date: Mon, 30 Jul 2012 23:12:28 +0100
From: Mark Murray <w.h.oami@example.com>
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Subject: Re: Formatted IO - Fortran style or similar.
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Date: 2012-07-30T23:12:28+01:00
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On 30/07/2012 10:59, Ian Clifton wrote:
> I’m not quite sure what facilities you’re after—I don’t know C’s
> printf()/scanf(), but presumably they are quite different from Fortran’s
> format control—but I suspect the answer is going to be “Ada’s approach
> is different” (see below).

The syntax isn't all that important; its the fine-grained method of
specifying output with a format + list_of_variables.

Fortran separates the format from the read/write statements containing
the list of variables, C's printf/scanf put the format string as the
first argument of the function call. With both, quite detailed I/O
lines can be specified with a reduction in function calling.

I like them because of the compactness:

printf("A=%d B=%6.3f C=0x%04X\n" A, B, C);

... rather than multiple calls.

>> I could have sworn I saw a PL/1-style "picture" version of this, but I'm
>> coming round to believing that this was "customer code", not standard
>> library.
>
> Here, you could be thinking about “Edited Output for Decimal types”,
> described in the ARM Appendix F.

Could be, thanks!

>> PS: Is it really the case that put(some_integer,16) will _always_
>> print the '16#9999#' format, and that there is on way _in_the_
>> _standard_library_ of *not* getting the '16#.....#' wrapper?
>> Yes, I know there are ways you can get rid of it (eg with a slice), or
>> by "rolling your own" - alternatives aren't my question here :-).
>
> I believe Ada’s approach is to specify the results of
> put(some_integer,16) sufficiently carefully that you can do such
> post‐processing with the provided string manipulation packages and be
> confident of the final result. In other words, what you are trying to
> avoid ARE the language’s facilities for doing this sort of thing. I ought
> to mention in passing, the Ada.Text_IO packages are a little
> controversial, many dislike them, but I believe they are under‐rated.

If that is the "Ada way", then so be it. :-)

I held back on that method as it felt "wasteful"; why generate
something if you know you don't need it? ("I want XXXX (hexadecimal),
why do I need to generate 16#XXXX# first?")

I suppose that learning a language's idioms are part of learning the
language. Thanks for the help!

M
-- 
Mark "No Nickname" Murray
Notable nebbish, extreme generalist.