Re: what languages Ada 9X compilers are being written in

Re: what languages Ada 9X compilers are being written in

[Jonathan Schilling]

Regarding the thread about what language Ada 9X compilers are being written
in,  DDC-I Ada compilers have always been written in Ada.  When work began
on upgrading to 9X, the question was reopened as to what language to use
for the components being built from scratch, with Ada (83 -> 9X), C, and
C++ all considered.  Overwhelmingly, the staff was in favor of Ada, and
that is what is being used.  Notably, the feeling on the side of Ada seemed
to be strongest amongst those who had used C or C++ on other projects!

Also, as a general rule (with notable exceptions I'm sure), compilers are 
best if written in their own language.  First, it means the compiler developers
will have a genuine "feel" for the language and its uses, rather than what
you get from just reading an LRM.  Second, it means the compiler developers wil
l
have to use their own compiler and their own tools, which is a great if
"selfish" incentive to make them even better.

-- 
Jonathan Schilling
DDC-I, Inc.
uunet!ddciiny!jls

Re: what languages Ada 9X compilers are being written in

[Wes Groleau X7574]

In article <C7GH0u.5o6@ddciiny.UUCP> jls@ddciiny.UUCP (Jonathan Schilling) writ
es:
>..... as a general rule (with notable exceptions I'm sure), compilers are 
>best if written in their own language.  First, it means the compiler developer
s
>will have a genuine "feel" for the language and its uses, rather than what
>.........

On the other hand, trying to write an Ada compiler in Ada has one quirk that
forces one to do something NOT typically done in Ada:  

I had to write a parser for a special-purpose language.  The easiest, most
readable way to read tokens for reserved words is to have an enumerated type
whose literals were all the reserved words, and read them with enumeration_io
and/or with RESERVED_WORD_TYPE'VALUE.  Unfortunately, some of the reserved
words are also Ada reserved words, so a few extra wierd string techniques had
to be used.  If the target language was actually Ada, the problem would
obviously be worse.

Re: what languages Ada 9X compilers are being written in

[Robert Dewar]

With respect to the idea of using an enumeration type and 'VAL to read and
parse keywords, it's cute, but no serious compiler would use such a technique
since it is likely to be seriously inefficient, and any gains in simplicity
are probably illusion in the context of a complete lexical scanner.