CODEWITHSUNDEEP
vhdl
Philippe
Philippe

Reputation: 3730

Are VHDL character substitutions ever used in real life?

VHDL allows the following substitutions, presumably because some computers might not support the vertical bar (or pipe symbol) (|) or the hash (or pound sign / number sign) (#):

case A|B can be written as case A!B

16#fff# can be written as 16:fff:

Any computer nowadays supports the vertical bar and the hash symbol, so I figured nobody uses these substitutions... Until somebody requested support for the exclamation mark.

My question: is this a lone case or are other people also using the exclamation mark as substitute for the vertical bar? Anybody using the colon?

Upvotes: 3

Views: 793

Answers (2)

Martin Thompson
Martin Thompson

Reputation: 16832

Data point 1: Not me :)

And I've never seen it as far as I recall in any code - nor was I taught it at any point (in fact, this is the first I knew of those substitutions).

I had a quick look in Ashenden's Designer's Guide to VHDL, and the ! alternative is not even mentioned when the | is introduced for case statements.

Upvotes: 2

AProgrammer
AProgrammer

Reputation: 52324

These are inherited from Ada (in which they are obsolescent since Ada95). The Ada83 Rationale says "For portability reasons, it is possible to write any program in a 56 character subset of the ISO character set." in which ISO character set must be understood as ISO-646, aka ASCII (well ISO-646 has provision for replacing some characters for national variant, ASCII can be understood as the US national variant of ISO-646)

There is a third replacement: % can be use instead of " as string delimitor (both must be replaced).

I seem to remember that EBCDIC is using | or ! for the same code point depending on the variant.

Upvotes: 1

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