While Loop in M Language Syntax

[dh76_PBI1]

Hello, 

I am getting so many syntax errors that I am hoping someone can guide me as to what should go where. It outputs a 0 followed by errors, at present. 

    CustomColumn = List.Generate(
        () => [
            i=0, 
            budget_index=0, 
            LastYearMax=List.Max(List.Select(RunningTotalList, each _ < #"BudgetTbl"{0}[Budget])), 
            result = 0,
            current_running_total = RunningTotalList{[i]},
            initial_condition = [current_running_total] < #"BudgetTbl"{0}[Budget],
            budget_condition = [current_running_total] < ([LastYearMax] + #"BudgetTbl"{[budget_index] + 1}[Budget]),
            last_year_running_total = RunningTotalList{[i]-1},
            last_year_condition = [last_year_running_total] < ([LastYearMax] + #"BudgetTbl"{[budget_index] + 1}[Budget])
            ],
        each [i] < List.Count(RunningTotalList),
        each [
            i = [i] + 1,
            LastYearMax = List.Max(List.Select(RunningTotalList, each _ < #"BudgetTbl"{[budget_index]}[Budget])),
            budget_index = Table.PositionOf(Table.Min(#"BudgetTbl"[Budget], each _ >= [current_running_total]) - 1),
            current_running_total = RunningTotalList{[i]},
            initial_condition = [current_running_total] < #"BudgetTbl"{0}[Budget],
            budget_condition = [current_running_total] < ([LastYearMax] + #"BudgetTbl"{[budget_index] + 1}[Budget]),
            last_year_running_total = RunningTotalList{[i]-1},
            last_year_condition = [last_year_running_total] < ([LastYearMax] + #"BudgetTbl"{[budget_index] + 1}[Budget]),
            result = 
                if [initial_condition] then [result] = #"BudgetTbl"{0}[Year]
                else if [budget_condition] then [result = #"BudgetTbl"{[budget_index] + 1}[Year]]
                else if [last_year_condition] then [result = #"BudgetTbl"{[budget_index] + 1}[Year], budget_index = [budget_index] + 1, LastYearMax = RunningTotalList{[i] - 1}]
                else 0
        ],
        each [result]
    )

Any help appreciated. 

[dh76_PBI1]

Thank you!

[spinfuzer · Accepted solution]

Simply the formulas and take advantage of being able to refer to previous value "[i]" and next value "i".

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("VczBCcAwDEPRXXzOwZaTtJ0lZP81Kgcq6PHBl9YyOLo1i3Db7XAUU5zFIV5/3iRcfIr4yBNScUZxiiBT20yyF/cL", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Year = _t, Budget = _t]),
    RunningTotalList = {10, 25, 75, 107, 167, 187, 192, 272, 287, 297, 346, 389, 410, 500, 554, 640, 693, 716, 720, 776},
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Year", Int64.Type}, {"Budget", Int64.Type}}),
    CustomColumn = List.Generate( () =>
        [
            i = 0, 
            j = 0, 
            current_budget = #"Changed Type"[Budget]{j}
        ],
        each [i] < List.Count(RunningTotalList),
        each [
            i = [i] + 1,
            j = if RunningTotalList{i} <= [current_budget] then [j] else [j] + 1,
            current_budget = if [j] <> j then RunningTotalList{[i]}*Byte.From(j <> 0) + #"Changed Type"[Budget]{[j]} else [current_budget]
        ],
        each #"Changed Type"[Year]{[j]} 
    )
in
    CustomColumn