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Re: Sum an array in a lambda.

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Joseph Hesse <joeh@gmail.com> writes:
> On 12/20/22 11:29, Öö Tiib wrote:
>> auto fp = [] (int x[])
>> ... is by language rules equivalent to ...
>> auto fp = [] (int *x)
>> ... so array length information is lost and range
>> based for has no idea what range you mean.
>> 
>>>
>> 
> In the following program, the array definition and range based for
> loop are in the same scope so it appears that the range based for loop
> sees the size of the array.  The following program compiles with the
> gnu compiler and runs correctly.  I am surprised that it works.
> =========================================
> #include <iostream>
> #include <vector>
> using namespace std;
> int main(){
>   int x[4] = {1, 2, 3, 4};
>   int sum = 0;
>   for(const int &i : x)
>       sum += i;
>   cout << "sum = " << sum << '\n';
>   return 0;
> }

Why are you surprised?

In `auto fp = [] (int x[])`, x is an array parameter, which is treated
as a pointer parameter.  That equivalence applies only to function
parameters.  In your example, you just have an array object.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for XCOM Labs
void Void(void) { Void(); } /* The recursive call of the void */

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Thread

Sum an array in a lambda. Joseph Hesse <joeh@gmail.com> - 2022-12-20 11:00 -0600
  Re: Sum an array in a lambda. Öö Tiib <ootiib@hot.ee> - 2022-12-20 09:29 -0800
    Re: Sum an array in a lambda. Joseph Hesse <joeh@gmail.com> - 2022-12-21 10:56 -0600
      Re: Sum an array in a lambda. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-21 10:32 -0800
        Re: Sum an array in a lambda. Joseph Hesse <joeh@gmail.com> - 2022-12-22 00:05 -0600
          Re: Sum an array in a lambda. Öö Tiib <ootiib@hot.ee> - 2022-12-22 00:00 -0800
            Re: Sum an array in a lambda. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-22 12:42 +0000
  Re: Sum an array in a lambda. Paavo Helde <eesnimi@osa.pri.ee> - 2022-12-20 20:03 +0200
  Re: Sum an array in a lambda. Juha Nieminen <nospam@thanks.invalid> - 2022-12-21 06:35 +0000
  Re: Sum an array in a lambda. Bonita Montero <Bonita.Montero@gmail.com> - 2022-12-22 19:55 +0100

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