Re: seq-union calling seq-reverse? (Emacs master 0cf0a2b98671: Add new sequence function 'seq-union')

[Stefan Kangas]

Štěpán Němec <stepnem@gmail.com> writes:

> +(cl-defgeneric seq-union (sequence1 sequence2 &optional testfn)
> +  "Return a list of all elements that appear in either SEQUENCE1 or 
> SEQUENCE2.
> +Equality is defined by TESTFN if non-nil or by `equal' if nil."
> +  (let ((accum (lambda (acc elt)
> +                 (if (seq-contains-p acc elt testfn)
> +                     acc
> +                   (cons elt acc)))))
> +    (seq-reverse
> +     (seq-reduce accum sequence2
> +                 (seq-reduce accum sequence1 '())))))
> +
>
> `seq-reverse' seems gratuitous here WRT the purpose of `seq-union'.

I have pushed a fix to make it use `nreverse' instead.  This is faster,
and in line with e.g. seq-partition, seq-uniq, etc.