Re: Building an Ada compiler

[bobduff@world.std.com (Robert A Duff)]

In article <4r023h$jt2@newsbf02.news.aol.com>, ErkoDJK <erkodjk@aol.com> wrote:
>Some friends and I have a crazy idea.  We want to build an Ada 95 compiler
>targeted for the Macintosh computer (without requiring Unix, like
>GNAT/GCC).  To that end, I would like to ask the Ada and compiler experts
>here (and anyone else who wishes to respond) for some information,
>including, just how insane are we?

From scratch?  Somewhere between 10 and 100 person-years, is my guess.
It depends on the expertise of the engineers, and how fancy you want to
make it (e.g. optimizations, debugging capabilities, etc).  This comes
from my experience on Ada compiler projects, and talking to other Ada
compiler writers.

>Self-effacing humor aside, just how big a project is an Ada 95 compiler? 
>Those of us planning to work on this project are all Ada software
>engineers with at least seven years of experience, but none of us are
>compiler experts. ...

In that case, probably closer to the upper-end of the above range.

Also, are you Ada language lawyers?  For example, read the Ada Issues
produced by the ARG.  If your response is "Heh?  What are these people
babbling about?" then you have a lot to learn about the language itself.
For another example, can you come up with an example off the top of your
head showing why it is impossible for the parser to tell the difference
between a normal string_literal and an operator_symbol?  That's
something that a normal Ada programmer wouldn't care about, but that a
compiler writer cares deeply about, since it affects the high-level
design.  That's just one little example.  All of these things can be
learned, of course, but it takes time.

IMHO, if you've never built a compiler, and don't know Ada like the back
of your hand, it would be foolish to build an Ada compiler as your first
try.

Anybody remember who said this (in regard to hand-made telescope
mirrors)?  It's easier to make a 3-inch mirror and a 5-inch mirror, than
to make a 5-inch mirror.

- Bob

P.S. Sorry to be so gloomy...