List Generate , how it iterates

[Dicken]

Hi, 
I have a question regardign how gen accumulates , I have an accumulation which re starts when 10 is reached / exceeded, 
So this works, 

let alist = {3} & List.Repeat({2} , 25) in
List.Generate( ()=> [ x = 0 , y = alist{0} ,z = 0 ] ,
each [x] < List.Count(alist) ,

each [ x = [x] + 1, z = alist{x} ,

y = if [y] + z > 10 then z else [y] + z] ,
each [y] )

so from this ; 

let alist = {3} & List.Repeat({2} , 25) in
List.Generate( ()=> [ x = 0 , y = alist{0} ,z = 0 ] ,
each [x] < List.Count(alist) ,
each [ x = [x] + 1,    y = [y] + alist{x}  ,  z = y ] ,
each [z] )

But if you try an if condtion; 

= let alist = {3} & List.Repeat({2} , 25) in
List.Generate( ()=> [ x = 0 , y = alist{0} ,z = 0 ] ,
each [x] < List.Count(alist) ,
each [ x = [x] + 1, y = [y] + alist{x} , z = if y > 10   then alist{x}   else y ] ,
each [z] )

 then the accumulation does not re start ? , but if the current value = ie 2 then 2 < 10 so [y] + alist{x} 
but that does not seem to be the case, not sure why , 
some advice help sought on this . 

Richard.

[Dicken]

Thanks, sorry for slow response. 

[Omid_Motamedise]

You can also solve this problem by List.Accumulate

let 
    alist = {3} & List.Repeat({2} , 25) 
in
List.Accumulate(alist, {0},(a,b)=> if List.Last(a)+b>10 then a&{b} else a& {List.Last(a)+b})

[ronrsnfld]

In your non-working snippet, your sequence will not repeat because you never reset "y". So once y>10 = true, it will always be >10 and z will always return alist{x}

let 
    alist = {3} & List.Repeat({2} , 25) 
in
    List.Generate( ()=> [ x = 0 , y = alist{0} ,z = 0 ] ,
    each [x] < List.Count(alist) ,
    each [ x = [x] + 1, 
           y = [y] + alist{x} , 
           z = if y > 10   
                    then alist{x}   
                    else y ] ,
    each [z] )

Try:

let 
    alist = {3} & List.Repeat({2} , 25) 
in
    List.Generate( ()=> [ x = 0 , y = alist{0} ,z = 0 ] ,
        each [x] < List.Count(alist) ,
        each [x = [x] + 1, 
              y = if [y] + alist{x} > 10 
                then alist{x} 
                else [y] + alist{x}, 
                z = y ] ,
        each [z] )

although you don't really need z at all

let 
    alist = {3} & List.Repeat({2} , 25) 
in
    List.Generate( ()=> [ x = 0 , y = alist{0}] ,
        each [x] < List.Count(alist) ,
        each [x = [x] + 1, 
              y = if [y] + alist{x} > 10 
                then alist{x} 
                else [y]+alist{x}] ,
        each [y] )

[Dicken]

I still don't see why the condition does not kick in as expected the third example, 
so this works y = if [y] + alist{x} > 10 then alist{x} else [y] + alist{x} ] works, 
but if [y] + alist{x} is declared as a variabel y  
 and then ; if     z = if  y > 10 then alistt{x}    it returns a different incorrect restult? 
that's the question, I not bothered about solving it just why the two operate differently

[ronrsnfld · Accepted solution]

As I wrote above: in that example you are never resetting y. So once y becomes greater than 10, y always remains greater than 10.

Therefore z will always be set to alist{x}