Re: Ada standard and maximum line lengths

[Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>]

On 01/27/2013 10:02 PM, Lucretia wrote:
>
> I was reading the Ada 2012 standard and found this, I was just wondering why
> there is a maximum line length, it's not like we parse the language a line at
> a time. Why not just accept it as a stream of tokens and if there are line
> breaks, ignore?

I presume that by "this", you're referring to ARM 2.2, where it says:

"An implementation shall support lines of at least 200 characters in length, not 
counting any characters used to signify the end of a line. An implementation 
shall support lexical elements of at least 200 characters in length. The maximum 
supported line length and lexical element length are implementation defined."

This does not impose a maximum line length; it imposes a minimum value for the 
maximum line length a compiler must accept. An implementation is free to accept 
lines of any length greater than this minimum length that it chooses, including 
no maximum line length. But since the maximum line length chosen by a compiler 
also defines the maximum identifier length accepted by the compiler, and few 
compilers are willing to accept identifiers of any length, most compilers will 
impose a maximum line length.

The importance of a minimum value for the longest line a compiler must accept in 
the standard is that it allows portable programs to be written. By not exceeding 
200-character lines, even if your compiler will accept them, you know that your 
program will be accepted by any compiler.

-- 
Jeff Carter
"If a sperm is wasted, God gets quite irate."
Monty Python's the Meaning of Life
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