Re: f95 interpreter

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:


[snip]


>There are very few true interpreters for programming languages. (Not
>counting command languages such as unix csh, sh, and DOS/Windows .BAT
>files.)
>
>Most are closer to incremental compilers, where at minimum each
>statement is compiled to an intermediate form, converting language
>tokens (keywords) to an internal form, and possibly user symbols
>(variable names) also. Most BASIC systems work like that, many
>compiling each line when it is entered. On the continuum between


          IME, no. They simply convert it to a tokenised form.


>compilers and interpreters, it is most of the way toward interpreters.


[snip]


>[Back in the early 1970s, IBM had two PL/I compilers, the X compiler
>which generated optimized machine code and the CK (checkout) compiler
>which generated bytecodes and interpreted them. They used the same
>front end and accepted the same input language. The CK compiler
>offered all of the nice debugging stuff you'd expect from an
>intepreter, full range checks, bogus pointers, type mismatches, all
>that. You could even tell CK to generate code with call stubs so you
>could run a mix of X and CK code if you wanted. Of course, high
>quality debugging support like that is now obsolete. -John]


          Grrr!


          How fast do you want your wrong answers?


Sincerely,


Gene Wirchenko
[Do keep in mind that back in those days the fast computers ran at 1 MHz,
so the difference in code speed could make the difference between a
minute-long run and an all-night run. But it is my impression that the
call stubs were mostly used to call code in precompiled libraries. -John]

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