Re: Form feed comment for pragma Page

[kst@thomsoft.com (Keith Thompson)]

In <evans-0406961641500001@ppp5.pgh.net> evans@evans.pgh.pa.us (Arthur Evans Jr) writes:
> Well, form feed (control-L) is an ASCII character and part of the
> standard character set, but I'm quite surprised to hear that it's a
> logical-end-of line, for two reasons:
> 
>   - If anything, it's-end-of page, not-end-of line.
> 
>   - And it's not even that.  The RM in A.10(8) is quite clear that the
>     standard does not specify which characters, if any, correspond to
>     logical end-of-line or end-of-page or end-of-file.
> 
> I'll agree that many implementations, probably most of them, choose to
> implement end-of-page using the ASCII form feed character, but the
> standard is silent on the subject.

RM A.10(8) refers to files processed by Text_IO, not to Ada source files;
there's no requirement that they're the same thing.  An Ada compiler
needn't use Text_IO to read source files.

The relevant paragraph is 2.2(2), which says:

    The text of a compilation is divided into lines.  In general,
    the representation for an end of line is implementation defined.
    However, a sequence of one or more format_effectors other than
    character tabulation (HT) signifies at least one end of line.

A format_effector is defined in 2.1(13) as one of HT, VT, CR, LF, and FF.
Thus a formfeed character *in an Ada source* must signify an end of line.

Note that the coded representation for these characters is also
implementation-defined.

-- 
Keith Thompson (The_Other_Keith) kst@thomsoft.com <*>
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