help needed with types

[danish-mehmood]

hey everyone i am reading the froebel code base and learning so much
but there are some types which are i can't understand can anyone tell what the following types are doing
-> one is 'λ' type (can not understand what its doing)
-> and the second is 'Widen' type
thanks

[MathisBullinger]

Hi Danish,

the λ type is just a shortcut for a function type. So the type λ is equivalent to the type (...args: any[]) => any or in other words a function that takes any number of arguments and returns anything. The type can also take two optional parameters: The first one is a list of the arguments the function accepts and the second is the function's return type. I.e. λ<[a: number, b?: string], number> is equivalent to writing (a: number, b?: string) => number. The same type is also exported under the name fun from types.ts.

The Widen type converts string unions to a generic string type and number unions to a generic number. So Widen<'a' | 'b'> returns the type string instead of the union 'a' | 'b' and the same is true for numbers. If the parameter is not a string or number then Widen just returns that parameter as is. So in a sense, it "widens" the stricter union types into their more generic equivalents.

Most of the types in types.ts are only meant to be used internally by the utilities in this library, hence the lack of documentation for most of them. But I have been thinking about cleaning them up a bit, adding documentation for every type, and moving them into a type-only library that froebel would depend on at some point.

[danish-mehmood]

hey mathis thanks for answering , i even emailed you , but you were so swift to reply thanks alot
and the idea of documenting the internal types as well is awesome
i am reading all the projects you have on github and learning so much