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Welcome to #monadicmonday! Let's start with a These/Ior monad.
`These` is a monad which expresses "inclusive-OR" relation:
These(A, B) = A + B + A * B.
These represents a simple idea: it can hold either value of type A, value of type B or both of them simultaneously.
`These` is a monad which expresses "inclusive-OR" relation:
These(A, B) = A + B + A * B.
These represents a simple idea: it can hold either value of type A, value of type B or both of them simultaneously.
It may be present in FP libraries under it's literal name "These" (Haskell, TypeScript), or under "Ior" name (like in Scala's `cats` package).
Take a look at the following function in TypeScript using These monad from fp-ts package by @GiulioCanti:
Take a look at the following function in TypeScript using These monad from fp-ts package by @GiulioCanti:
@GiulioCanti Now let's look at the examples. Note that we need to provide all possible "handlers" to `fold` function,
so the monad could be reduced to a single value.
so the monad could be reduced to a single value.
@GiulioCanti Now let's transform this code to a full example:
@GiulioCanti Finally, let's run our example!
