Wrapping a function in maybe will modify it to return a maybe value. If
the function would normally return an error or warning the modified function
will return a 'Nothing' value, otherwise it will return a 'Just' value.
If a predicate function is provided with the parameter ensure, if the
predicate returns TRUE when evaluated on the return value of the function,
then a 'Just' value will be returned by the modified function, otherwise
it will return a 'Nothing' value.
Usage
maybe(.f, ensure = function(a) TRUE, allow_warning = FALSE)
Arguments
- .f
A function to modify
- ensure
A predicate function
- allow_warning
Whether warnings should result in 'Nothing' values
Value
A function which returns maybe values
Examples
maybe(mean)(1:10)
#> Just
#> [1] 5.5
maybe(mean, allow_warning = TRUE)("hello")
#> Warning: argument is not numeric or logical: returning NA
#> Just
#> [1] NA
maybe(sqrt)("hello")
#> Nothing
maybe(sqrt, ensure = not_infinite)(-1)
#> Nothing