Re: Integral types and own type definitions (was Re: Suggested method for returning a string from a C program?)

On 2025-03-31, Kaz Kylheku <643-408-1753@kylheku.com> wrote:

On 2025-03-31, Alan Mackenzie <acm@muc.de> wrote:

Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:
>
[ .... ]
>

I don't know of any language that uses "-" for both negation (prefix,
one operand) and subtraction (infix, two operands) and treats -5
as a single token rather than a unary minus operator applied to the
constant/literal "5".

>
How about Lisp?  The unary operator is (- 5), the binary (- 10 5).
>
It doesn't match your second parenthetical remark ("infix") but
otherwise it does.

>
Lisp could be infix if we want with some macro:
>
 (infix-environment
   ... (10 - (a * 3)) ...)

I had been toying with the idea in my mind for a while, and this gave me the
impetus to get it working. It's very simple if you extend the Lisp dialect with
a suitable code walking hook.

Working, advanced proof of concept:

  $ ./txr -i infix.tl
  TXR's no-spray organic production means every bug is carefully removed by hand.
  1> (ifx (let ((a 1) (b 2) (c 3))
            ((a + b) * 3)))
  9

I'm going to post about this in more detail in comp.lang.lisp, where
it is topical.

--
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