| Title: | A Ternary Conditional Operator for R |
| Version: | 0.1.2 |
| Description: | A small language extension for succinct conditional assignment using '?' and ':', emulating the conditional ternary operator syntax using in C, Java, JavaScript and other languages. |
| License: | MIT + file LICENSE |
| Encoding: | UTF-8 |
| RoxygenNote: | 7.1.2 |
| URL: | https://github.com/grddavies/rtern |
| BugReports: | https://github.com/grddavies/rtern/issues |
| Suggests: | covr, testthat (≥ 3.0.0), spelling, lifecycle |
| Config/testthat/edition: | 3 |
| Language: | en-US |
| Imports: | utils, rlang |
| NeedsCompilation: | no |
| Packaged: | 2022-01-24 17:58:24 UTC; Gethin.Davies |
| Author: | Gethin Davies [aut, cre] |
| Maintainer: | Gethin Davies <grd.davies@gmail.com> |
| Repository: | CRAN |
| Date/Publication: | 2022-01-24 18:12:43 UTC |
Succinct conditional evaluation and assignment
Description
![[Experimental]](./figures/lifecycle-experimental.svg)
? is an in-line if/else operator
Usage
lhs ? rhs
Arguments
lhs |
A logical expression, vector or matrix. |
rhs |
A pair of values separated by a colon i.e. |
Details
The syntax for ? is as follows:
condition ? value_if_true : value_if_false
The condition is evaluated TRUE or FALSE as a Boolean expression.
On the basis of the evaluation of the Boolean condition, the entire expression
returns value_if_true if condition is true, but value_if_false otherwise.
In the case where the condition is a vector/matrix of Boolean values, the
function returns a vector/matrix where each element is either value_if_true
or value_if_false based on the truthiness of the elements of the object on
the left-hand side. In these cases the behaviour of ? mimics ifelse.
Who has time for if/else?
Value
One of the values in rhs, depending on the truthiness of lhs.
Examples
# Conditional evaluation
4 > 3 ? "it_was_true":"it_was_false"
# > "it_was_true"
FALSE ? "it_was_true":"it_was_false"
# > "it_was_false"
# Vectorised evaluation
c(4, 2) < 3 ? "it_was_true":"it_was_false"
# > "it_was_false" "it_was_true"
# Conditional assignment with `<-`
x <- 4 > 3 ? "it_was_true":"it_was_false"
x
# > "it_was_true"
# Conditional assignment with `=`
y <- 3 > 4 ? "it_was_true":"it_was_false"
y
# > "it_was_false"
# Chaining `?` statements
z <- FALSE ? "true":(FALSE ? "false,true":(TRUE ? "false,false,true":"all false"))
z
# > "false,false,true"
Check if an expression is an assignment
Description
Takes an expression that has been cast to a list and returns true if using
left-assignment with either <- or =
Usage
is_assignment(parse_tree)
Arguments
parse_tree |
An unevaluated expression as a list |
Value
A logical