[m-rev.] for review: Make string.left and string.right not create unused substrings.

[Mark Brown]

Did this have a log message? Otherwise fine.

On Wed, Oct 23, 2019 at 3:03 PM Peter Wang <novalazy at gmail.com> wrote:
>
> ---
>  library/string.m | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/library/string.m b/library/string.m
> index 97b005841..4363c0c5f 100644
> --- a/library/string.m
> +++ b/library/string.m
> @@ -4171,7 +4171,7 @@ left(S1, N) = S2 :-
>      left(S1, N, S2).
>
>  left(String, Count, LeftString) :-
> -    split(String, Count, LeftString, _RightString).
> +    between(String, 0, Count, LeftString).
>
>  left_by_codepoint(String, Count) = LeftString :-
>      left_by_codepoint(String, Count, LeftString).
> @@ -4184,8 +4184,8 @@ right(S1, N) = S2 :-
>
>  right(String, RightCount, RightString) :-
>      length(String, Length),
> -    LeftCount = Length - RightCount,
> -    split(String, LeftCount, _LeftString, RightString).
> +    Start = Length - RightCount,
> +    between(String, Start, Length, RightString).
>
>  right_by_codepoint(String, RightCount) = RightString :-
>      right_by_codepoint(String, RightCount, RightString).
> --
> 2.23.0
>
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