Re: Re: What attributes of a programming language simplify its implementation? RPN?

gah4 <gah4@u.washington.edu> writes:
>On Tuesday, November 15, 2022 at 1:15:04 PM UTC-8, minf...@arcor.de wrote:
>> Citing its inventor Chuck Moore:
>> "By permitting the program to dynamically modify its control language,
>> we mark a qualitative change in capability. In a sense, our program
>> has evolved into a meta-language which we apply to the application.”
>
>PostScript is also based on an RPN language interpreter, though I
>am not sure that the above quotes apply in the same way.


IMO it does.


>One that I know about PostScript, and maybe not be true for Forth,
>is the bind operator.


Postscript uses run-time name binding (like Lisp), Forth binds the
names statically. Postscript's bind makes Postscript more Forth-like,
but note that it statically binds only operators (built-ins), names
that are bound to non-operators are still resolved dynamically.


>Before def, which defines a new operator, you can bind, which binds any
>operators inside the new definition to their current value. (I believe it
>also optimizes them to the address of the routine, saving the time for searching
>for the name in a symbol table.)


Yes, it replaces the names that are bound to operators in the
definition with the operators. So there is no name lookup for those
at run-time.


>So we wrote a header with new macros, and which then redefined
>def such that later macros wouldn't override them.
>(I think we always called them macros, not operators, but I am not
>sure by now what the right name is.)


procedures


>The Sun boot roms also use Forth, or something Forth-like as the
>built-in control language.


Yes, the base language of Open Firmware is Forth.


- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/

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