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J.2 Allowed Replacements of Characters
replacements are allowed for the vertical line, number sign, and quotation
- A vertical line character
(|) can be replaced by an exclamation mark (!) where used as a delimiter.
- The number sign characters
(#) of a based_literal can be replaced
by colons (:) provided that the replacement is done for both occurrences.
To be honest: The intent
is that such a replacement works in the Value and Wide_Value attributes,
and in the Get procedures of Text_IO, so that things like ``16:.123:''
- The quotation marks
(") used as string brackets at both ends of a string literal can
be replaced by percent signs (%) provided that the enclosed sequence
of characters contains no quotation mark, and provided that both string
brackets are replaced. Any percent sign within the sequence of characters
shall then be doubled and each such doubled percent sign is interpreted
as a single percent sign character value.
These replacements do not change the meaning
of the program.
Reason: The original
purpose of this feature was to support hardware (for example, teletype
machines) that has long been obsolete. The feature is no longer necessary
for that reason. Another use of the feature has been to replace the vertical
line character (|) when using certain hardware that treats that character
as a (non-English) letter. The feature is no longer necessary for that
reason, either, since Ada 95 has full support for international character
sets. Therefore, we believe this feature is no longer necessary.
Users of equipment that still
uses | to represent a letter will continue to do so. Perhaps by next
the time Ada is revised, such equipment will no longer be in use.
that it was never legal to use this feature as a convenient method of
including double quotes in a string without doubling them -- the string
%"This is quoted."%
not legal in Ada 83, nor will it be in Ada 95. One has to write:
"""This is quoted."""
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