Just: Represent values that exist.
In Teresa00/hfmAnnotation: HFM Internal Package for Annotations

Description Usage Arguments Format Details Value See Also Examples

One of the choice types for a Maybe monad (the other being Nothing)

Just(a)

`a`	A value of any non-null type

Just :: a -> Maybe a

Based off the Maybe monad in Haskell and Elm but similar in construction to the result "monad" supplied by purrr::safely(). A Maybe monad is a choice type: it is either Just(a_value) or it is Nothing(). It can be used to document optional arguments, force proper error handling, and deal with lists/records with optional entries. It can be useful if you have a value that is only filled in sometimes. Or if a function takes a value sometimes, but does not absolutely need it. Or if a function would otherwise return a NULL. The Maybe type reminds users of your code to remember to handle both possible states: when the value exists and when it does not.

An Maybe type (a wrapper around the original value of type 'a')

Other Maybe type: Nothing

safer_division <- function(x, y) { if (y == 0) { Nothing() } else { Just(x / y) } }
safer_division(1, 2) # Just(0.5)
safer_division(1, 0) # Nothing()

## Not run: safer_division(1, NULL)
# Runtime error:
# ... argument is of length zero