Why would it take so long to write an Ada compiler?

Why would it take so long to write an Ada compiler?

[Mike]

Hello,

I've read somewhere that to make an Ada95 compliant compiler, 50 years-man of 
work are generally considered what is necessary.

How is this huge quantity of development time justified? Perhaps required for
the standard library?

Greets,
Mike

Re: Why would it take so long to write an Ada compiler?

[AG]

"Mike" <spamnotme@invalid.com> wrote in message
news:MPG.1865cca835f2ccee98991a@News.CIS.DFN.DE...
>
> Hello,
>
> I've read somewhere that to make an Ada95 compliant compiler, 50 years-man
of
> work are generally considered what is necessary.
>
> How is this huge quantity of development time justified? Perhaps required
for
> the standard library?

I'll bite this time ;) Do you really consider 50 man-years a *lot* for a
compiler?
Let's see ... that equals 25 people for 2 years ... Hmmm, including all the
overhead
and what not. Of course that must include QA too. Not to mention some
regular
operational overhead and the chance/risk of failure which you would also
have
to provide for (in man-years, that is, since someone would need to handle
that).

Re: Why would it take so long to write an Ada compiler?

[Adrian Hoe]

AG wrote:

> "Mike" <spamnotme@invalid.com> wrote in message
> news:MPG.1865cca835f2ccee98991a@News.CIS.DFN.DE...
> 
>>Hello,
>>
>>I've read somewhere that to make an Ada95 compliant compiler, 50 years-man
>>
> of
> 
>>work are generally considered what is necessary.
>>
>>How is this huge quantity of development time justified? Perhaps required
>>
> for
> 
>>the standard library?
>>
> 
> I'll bite this time ;) Do you really consider 50 man-years a *lot* for a
> compiler?
> Let's see ... that equals 25 people for 2 years ... Hmmm, including all the
> overhead
> and what not. Of course that must include QA too. Not to mention some
> regular
> operational overhead and the chance/risk of failure which you would also
> have
> to provide for (in man-years, that is, since someone would need to handle
> that).
> 
> 
> 

or 50 people for a year... or 100 people for 0.5 years? That's 
mystical man-year... :-)

-- 
type Dmitry is new Adrian;           -- Adrian Hoe
                                      -- http://adrianhoe.com
                                      -- Remove *nospam* to email

Re: Why would it take so long to write an Ada compiler?

[steve_H]

Mike <spamnotme@invalid.com> wrote in message news:<MPG.1865cca835f2ccee98991a@News.CIS.DFN.DE>...
> Hello,
> 
> I've read somewhere that to make an Ada95 compliant compiler, 50 years-man of 
> work are generally considered what is necessary.
> 
> How is this huge quantity of development time justified? Perhaps required for
> the standard library?

50 man-hrs (or should that be 50 person-hrs?) is nothing for a 
commerical compiler. 

Do you how many person-hrs was spend on the first IBM PLI compiler? 
I do not remember the exact number, but I remember reading that 
it was a huge effort and probably the most costly compiler ever made. 
any one knows?

compilers are hard. code generation and optimization is the hardest
part I would think. lex and yacc can do most of the front work. GNAT
does not use lex and yacc. 

Ada compilers are harder on average than others becuase the language 
is big, but I would guess an Ada compiler is no more
complex than a C++ compiler, and probably less so. C compilers are
probably the least hard to build.

Re: Why would it take so long to write an Ada compiler?

[Frank J. Lhota]

"steve_H" <nma124@hotmail.com> wrote in message
news:8db3d6c8.0212151923.12bf6052@posting.google.com...
> Mike <spamnotme@invalid.com> wrote in message
news:<MPG.1865cca835f2ccee98991a@News.CIS.DFN.DE>...
> compilers are hard. code generation and optimization is the hardest
> part I would think. lex and yacc can do most of the front work. GNAT
> does not use lex and yacc.

A lot, possibly most, commercial compilers do not use lex and yacc. The
problem with yacc is the "bottom up" approach it takes to program parsing.
"Top Down" parsing makes it easier to generate good error messages.

Re: Why would it take so long to write an Ada compiler?

[faust]

 Mike <spamnotme@invalid.com> ,  emitted these fragments:

>
>Hello,
>
>I've read somewhere that to make an Ada95 compliant compiler, 50 years-man of 
>work are generally considered what is necessary.
>
>How is this huge quantity of development time justified? Perhaps required for
>the standard library?

Read Hoare's Turing Award lecture, "The Emperor's new clothes".
He argues that it is because of the ad hoc way and unprincipled way
features were added onto what finally became Ada.

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