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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