plusto operator definition missing?

[Jose E. Marchesi]

Yes, will fix :)

> Just to confirm...
>
> On Mon, Jul 14, 2025 at 7:20 AM chris hermansen <clhermansen@gmail.com>
> wrote:
>
>> Good day, Jose & list;
>>
>> 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.
>>>
>>
>> So I tried this, but I think it does not work as expected.
>>
>> Again, referring to Lindsey p. 244
>>
>> a +=: b
>>
>> is supposed to be equivalent to
>>
>> b := a + b
>>
>> That is, the point of plusto is to prepend rather than append.
>>
>> But it seems like GNU Algol 68 is generating
>>
>> b := b + a
>>
>> Perhaps I've missed something?
>>
>>
> Indeed the Revised Report shows this on page 138:
>
> q) op ⦓ plusab, +: = ⦔ = (ref string a, string b) ref string : a := a+ b;
> r) op ⦓ plusto, +=: ⦔ = (string a, ref string b) ref string: b := a+ b;
> s) op ⦓ plusab, +: = ⦔ = (ref string a, char b) ref string: a +:= string
> (b);
> t) op ⦓ plusto, +=: ⦔ =  (char a, ref string b) ref string: string (a) +=:
> b;