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Re: Format's C
- To: GSB at MIT-ML
- Subject: Re: Format's C
- From: Guy.Steele at CMU-10A
- Date: Wed ,22 Oct 80 13:55:00 EDT
- Cc: lisp-forum at MIT-MC
In answer to your query about FORMAT's C operation:
I suggest that the following informal definitions hold:
~C Prints the argument as a character in the most concise format
that will be unambiguous to a human reader and consistent with
the conventions of his programming environment.
Example: if alpha and beta are not available, one might print
the character with ASCII code 30 octal as "C-X" or perhaps
as "CTRL/X", depending on the conventions of the programming
environment. "C-X" might be preferred on grounds of conciseness.
"^X" would also be acceptable.
~:C Prints the argument as a lengthy but English-readable (and therefore
pronounceable) name. Any "keywords" or "special names" should
be capitalized full English words (to get all lowercase or all
uppercase one can use STRING-DOWNCASE or STRING-UPCASE or whatever).
The separator of choice is "-".
[Footnote: I nearly tore into the LISP Machine's FORMAT to add
uparrow and downarrow as modifer characters. The idea was that
uparrow would mean upper-case output, downarrow lower-case, and both
together would mean capitalized. I decided not to, because the arrows
are not standard ASCII characters, and also to avoid arrest on the
grounds of unwarranted baroqueness.]
Examples: Control-X, Meta-Space, Tab
~:@C Does the same thing, but adds a parenthetical remark describing how
to type the character if in the judgement of the implementor it
may not be obvious to the user how to input that character from the
keyboard he is using.
Examples: Control- (Top-A) [MIT keyboard]
Control-_ (Shift--) [stupid kbds where - and _ look alike]
~@C Prints the argument as a character in such a way that READ can
reconstruct the argument, or its logical equivalent, from the output.
Subject to this requirement, the output should be readable and concise
to whatever extent possible.
Examples: #/X #\RETURN #\RETURN #,(CONTROL #\RETURN)
Do these general descriptions seem reasonable?