plusto operator definition missing?

[Jose E. Marchesi]

> Thank you Jose,
>
> On Sun, Jul 13, 2025 at 1:24 PM Jose E. Marchesi <jemarch@gnu.org> wrote:
>
>>
>> > Hello all,
>> >
>> > I was going through Lindsey a couple of days ago and noticed the plusto
>> > operator definition on p. 244.  Here is what it says:
>> >
>> > operator priority mode of a  mode of b  mode of result  meaning
>> > plusto       1      string  ref string    ref string   b := a + b
>> > +=:                  char   ref string    ref string
>> >
>> > (I hope that shows up ok in peoples' email; I did it in fixed width text)
>> >
>> > I have a version of the procedure "whole" that I use with GNU Algol 68
>> that
>> > has the line
>> >
>> > digit_string := digit_char + digit_string
>> >
>> > in it, and I thought I'd try +=: instead, as in:
>> >
>> > digit_string +=: digit_char
>> >
>> > However, ga68 complains:
>> >
>> > testl.a68:277:50: error: CHAR cannot be coerced to REF STRING in this
>> > context
>> >   277 |                                 digit_string +=: digit_char;
>> >
>> > I am supposing that this is due to not having the second version of the
>> > operator defined - the one that works with a char on the right hand side.
>> >
>> > Am I missing something?  Thanks in advance.
>>
>> I think you mean:
>>
>>     digit_char +=: digit_string;
>>
>> Which works as expected.
>>
>
> My apologies.  Too many years of admiring the sacred nature of the left
> hand side...

:)

MARY had right-associative assignations, which actually made it possible
to treat them as regular dyadic operators and therefore overloadable:

    foo =: bar;

instead of:

    bar := foo;