Retrieve matching values from branch to leaf - list

Question

So im trying to make a tree with companies as the branch and subcompanies of the company as leafs.
Every company/subcompany consists of a name, a gross income and a list with their subcompanies.
I've made a function that returns a tuple with (name,gross income) for all the companies/subcompanies in the company tree.
What I would like to do now, is to find the total income for a certain company/subcompany, which means that the function should add all the subcompanies gross income together with the companies and return the result. It should only have a string as input (the name of the company).
type Department = a' list
and a' = | SubDep of string * float
| Company of string * float * Department;;
let company =
Company("Arla", 1000.0, [SubDep("Karolines Køkken", 500.0);
Company("Lurpak", 200.0, [SubDep("Butter",100.0); SubDep("Milk", 100.0)]);
SubDep("Arla Buko", 100.0);
Company("Riberhus", 200.0, [SubDep("Cheese",200.0)])
]);;
So an example run should be:
companyTotalIncome "Arla" company;;
And the result should be: 2400

Answer 1

To sum everything up you can do something like this (don't really know why you'll need the name of the company in here as for your example you just summed it all up):
let rec depIncome =
function
| SubDep (_, income) -> income
| Company (_,income, sub) -> income + totalIncome sub
and totalIncome =
List.sumBy depIncome
but your data structures are real strange (why list of companies a department?)
I would do maybe like this:
type Department =
{ name : String
income : float
}
type Company =
{ name : String
departmens : Department list
subCompanies : Company list
}
and then
let rec income company =
company.departments |> List.sumBy (fun d -> d.income }
+ company.subCompanies |> List.sumBy income
of course you can move the income to the company too (or add one there too) - I really don't know what you want to do - just my 5cts.