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attempt
Colin Fay
2020-05-03
Introduction to {attempt}
{attempt}
Tools for defensive programming, inspired by {purrr} mappers and based on {rlang}.
{attempt} is designed to handle the cases when something / someone attempts to do something it shouldn’t.
For example:
- an attempt to run a
log("a") (error)
- an attempt to connect to a web API without an internet connexion (error)
- an attempt to
paste() "good morning" and iris (message/warning)
- …
{attempt} provides several condition handlers, from try catch to simple message printing.
{attempt} only depends on {rlang}, and every function is design to be fast, making it easy to implement in other functions and packages.
Install
From CRAN:
install.packages("attempt")
The dev version:
install.packages("attempt", repo = "https://colinfay.me/ran", type = "source")
Using {attempt}
{attempt} provides four families of functions :
- try catch
- adverbs
- if
- conditions handlers
try catch
Try catch functions are a family of functions which are used to deal with errors and warnings.
attempt behaves like base::try, except that it allows custom message printing.try_catch is a wrapper around tryCatch that has a consistent grammar and allows the use of mappers.try_catch_df returns a tibble with the call, the error message if any, the warning message if any, and the value of the evaluated expression or “error”. The values will always be contained in a list-column.map_try_catch and map_try_catch_df allow to map on a list of arguments to be evaluated by the function in fun.
adverbs
Adverbs take a function and return a modified function.
silently transforms a function so that when you call this new function, it returns nothing unless there is an error or a warning.surely transforms a function so that when you call this new function, it calls attempt().with_message and with_warning take a function, and add a warning or a message to it.
if
if_none, if_any and if_all test the elements of the list.if_then perfoms a “if this then that”.if_else is a wrapper around base::ifelse() that works with mappers.
conditions
stop_if, warn_if and message_if are easy to use functions that send an error, a warning or a message if a condition is met.- they have a counterpart in
_if_not, and _if_all, _if_any and _if_none.
About mappers
Mappers are functions built like one sided formulas.
In other words, ~ .x + 2 is the equivalent of function(x) return(x + 2).
The first argument in a mapper need to be .x.
More on mappers.
These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.