strangest systems I've sent email from

Mouse mouse at Rodents-Montreal.ORG
Sun May 22 08:16:11 CDT 2016

>> Also, PostScript has a lot of language syntax, whereas FORTH has
>> immediate words that act like language syntax.  (The difference is
>> that FORTH makes it possible to change those words, thereby changing
>> the apparent syntax.)
> What do you mean by that?

Consider a simple definition

: foo swap - ;  ( inverted subtraction )
/foo { exch sub } def  % inverted subtraction

(The first is FORTH[%], the second PostScript.)  Each of these has some
"syntax" bits.  In FORTH, :, ;, (, and ).  In PostScript, the leading
/, {, }, and %.

The difference is that in FORTH, you can create new immediate words
and/or redefine the existing ones; : can do something other than
beginning the definition of a word, and you can arrange to begin the
definition of a word with something other than :.  In PostScript, none
of this is mutable short of hacking on the underlying implementation
(and if you do that the result isn't PostScript any longer).

[%] I think.  I don't really know FORTH; does it use - for subtraction?

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