plusto operator definition missing?

[Jose E. Marchesi]

> 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.