Re: List and String concatenation speed.

Hello.
I've decided to use FFI for String.^.
However, the speed has not been increased (slowed down, in fact).
The code is lower. I think I've done everything properly?

C:

#include <sys/types.h>
#include <string.h>

void string_concat_memmove(void *dst, const void *src1, size_t len1, const
void *src2, size_t len2) {
    memmove(dst, src1, len1);
    dst += len1;
    memmove(dst, src2, len2);
    return;
}


SML:

    val string_concat_memmove = _import "string_concat_memmove" :
Word8.word array * string * int * string * int -> unit;

    fun op ^ (a: string, b: string): string =
        let
            val a_length = String.size a
            and b_length = String.size b
        in
            if a_length = 0 then b else
            if b_length = 0 then a else
            let
                val arr = Word8Array.array(a_length + b_length, 0w0)
            in
                string_concat_memmove(arr, a, a_length, b, b_length);
                Byte.bytesToString (Word8Array.vector arr)
            end
        end

Best Regards.
Nick.

2016-08-29 16:46 GMT+03:00 Kostirya <[email protected]>:

> Yes. Poly/ML use memmove to to implement String.^
>
>
> 2016-08-29 16:21 GMT+03:00 Matthew Fluet <[email protected]>:
>
>> >> poly --script string_concat.sml
>> > 0.462269
>> >
>> >> mlton string_concat.sml && ./string_concat
>> > 2.713323
>>
>> It looks like Poly/ML uses memmove to implement String.^, which would
>> be more efficient for character sequences.
>>
>
>

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