Hi all,
given this code:

import std.algorithm.iteration : sum, cumulativeFold;

void main()
{
	double[5] a;
	a = 0;
	foreach(el; a) assert(el == 0);
	a[0] = 1.0;
	a[1] = 2.0;
	a[2] = 3.0;
	a[3] = 4.0;
	a[4] = 5.0;
	foreach(el; a) assert(el != 0);
	auto asum = a[].sum;
	auto jProbs = a[].cumulativeFold!((a, b) => (a + b)/asum);
}

the last line does not compile.

I found
http://forum.dlang.org/post/mailman.4097.1499105927.31550.digitalmars-d-bugs@puremagic.com
and
https://issues.dlang.org/show_bug.cgi?id=11886

What I do not understand, how my example differs from the fixed bug?

On Monday, 18 September 2017 at 14:45:25 UTC, Alex wrote:
> Hi all,
> given this code:
>
> import std.algorithm.iteration : sum, cumulativeFold;
>
> void main()
> {
> 	double[5] a;
> 	a = 0;
> 	foreach(el; a) assert(el == 0);
> 	a[0] = 1.0;
> 	a[1] = 2.0;
> 	a[2] = 3.0;
> 	a[3] = 4.0;
> 	a[4] = 5.0;
> 	foreach(el; a) assert(el != 0);
> 	auto asum = a[].sum;
> 	auto jProbs = a[].cumulativeFold!((a, b) => (a + b)/asum);
> }
>
> the last line does not compile.
>
> I found
> http://forum.dlang.org/post/mailman.4097.1499105927.31550.digitalmars-d-bugs@puremagic.com
> and
> https://issues.dlang.org/show_bug.cgi?id=11886
>
> What I do not understand, how my example differs from the fixed bug?

asum is a lazy range and the error comes from this.
Let's say that if you replace  asum by 1.23 then the code compiles.

On 09/18/2017 08:25 PM, user1234 wrote:
> On Monday, 18 September 2017 at 14:45:25 UTC, Alex wrote:
[...]
>> import std.algorithm.iteration : sum, cumulativeFold;
>>
>> void main()
>> {
>>     double[5] a;
[...]>>     auto asum = a[].sum;
[...]
> asum is a lazy range and the error comes from this.

asum is not a range. It's a double.

> Let's say that if you replace  asum by 1.23 then the code compiles.

Doesn't work for me. This still fails compilation with the same error:

----
import std.algorithm.iteration : sum, cumulativeFold;
void main()
{
    double[5] a;
    auto asum = 1.23;
    auto jProbs = a[].cumulativeFold!((a, b) => (a + b)/asum);
}
----

On Monday, 18 September 2017 at 18:49:54 UTC, ag0aep6g wrote:
> On 09/18/2017 08:25 PM, user1234 wrote:
>> On Monday, 18 September 2017 at 14:45:25 UTC, Alex wrote:
> [...]
>>> import std.algorithm.iteration : sum, cumulativeFold;
>>>
>>> void main()
>>> {
>>>     double[5] a;
> [...]>>     auto asum = a[].sum;
> [...]
>> asum is a lazy range and the error comes from this.
>
> asum is not a range. It's a double.
>
>> Let's say that if you replace  asum by 1.23 then the code compiles.
>
> Doesn't work for me. This still fails compilation with the same error:
>
> ----
> import std.algorithm.iteration : sum, cumulativeFold;
> void main()
> {
>     double[5] a;
>     auto asum = 1.23;
>     auto jProbs = a[].cumulativeFold!((a, b) => (a + b)/asum);
> }
> ----

Aw right, i had put 1.23 directly in the lambda. So, OP, you can dismiss my comment.

On Monday, 18 September 2017 at 18:49:54 UTC, ag0aep6g wrote:
>
> Doesn't work for me. This still fails compilation with the same error:
>
> ----
> import std.algorithm.iteration : sum, cumulativeFold;
> void main()
> {
>     double[5] a;
>     auto asum = 1.23;
>     auto jProbs = a[].cumulativeFold!((a, b) => (a + b)/asum);
> }
> ----

So, this is a bug, isn't it? I assume, I should file it then...

On Monday, 18 September 2017 at 21:58:39 UTC, Alex wrote:
> On Monday, 18 September 2017 at 18:49:54 UTC, ag0aep6g wrote:
>>
>> Doesn't work for me. This still fails compilation with the same error:
>>
>> ----
>> import std.algorithm.iteration : sum, cumulativeFold;
>> void main()
>> {
>>     double[5] a;
>>     auto asum = 1.23;
>>     auto jProbs = a[].cumulativeFold!((a, b) => (a + b)/asum);
>> }
>> ----
>
> So, this is a bug, isn't it? I assume, I should file it then...

I have this same issue. Anyone have any thoughts on a workaround?

For example, my attempt at an exponential moving average doesn't compile:
auto ema(Range,T) (Range rng, int period, T seed) {
    return rng.cumulativeFold!((a,b) => a+(2.0/(period+1))*(b-a))(seed.to!double);
}

So I ended up with this:
auto ema(Range,T) (Range rng, int period, T seed) {
    struct EMA(Range) {
        double currentValue;
        double weighting;
        Range rng;
        this (Range r, int p, double s) {
            currentValue = s;
            weighting = 2.0 / (p+1);
            rng = r;
        }
        auto front() { return currentValue; }
        auto popFront() {
            rng.popFront;
            if (!rng.empty){
                currentValue += (rng.front - currentValue)*weighting;
            }
        }
        auto empty() { return rng.empty; }
    }
    return EMA!Range(rng,period,seed.to!double);
}

Thanks,

Jordan

On Friday, 23 March 2018 at 03:38:22 UTC, Jordan Wilson wrote:
>
> I have this same issue. Anyone have any thoughts on a workaround?
>
For completeness:
https://issues.dlang.org/show_bug.cgi?id=17841