Wrapping a function in perhaps will modify it to return the expected value
or a default value in some circumstances. If the function would normally
return an error or warning the modified function will return a default value,
otherwise it will return the expected 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 the expected value will
be returned by the modified function, otherwise it will return the default
value.
Usage
perhaps(.f, default, ensure = function(a) TRUE, allow_warning = FALSE)
Arguments
- .f
A function to modify
- default
A default value
- ensure
A predicate function
- allow_warning
Whether warnings should result in the default value
Value
A function which returns the expected value or the default value
Examples
perhaps(mean, default = 0)(1:10)
#> [1] 5.5
perhaps(mean, default = 0, allow_warning = TRUE)("hello")
#> Warning: argument is not numeric or logical: returning NA
#> [1] NA
perhaps(sqrt, default = 0)("hello")
#> [1] 0
perhaps(sqrt, default = 0, ensure = not_infinite)(-1)
#> [1] 0