| Title: | List Comprehensions |
| Version: | 0.4.1 |
| Description: | An implementation of list comprehensions as purely syntactic sugar with a minor runtime overhead. It constructs nested for-loops and executes the byte-compiled loops to collect the results. |
| License: | MIT + file LICENSE |
| Encoding: | UTF-8 |
| RoxygenNote: | 7.1.2 |
| Suggests: | testthat |
| Imports: | rlang, compiler |
| URL: | https://github.com/dirkschumacher/listcomp |
| BugReports: | https://github.com/dirkschumacher/listcomp/issues |
| NeedsCompilation: | no |
| Packaged: | 2022-01-31 15:50:41 UTC; dsp |
| Author: | Dirk Schumacher [aut, cre, cph] |
| Maintainer: | Dirk Schumacher <mail@dirk-schumacher.net> |
| Repository: | CRAN |
| Date/Publication: | 2022-01-31 16:10:02 UTC |
List comprehensions
Description
Create lists of elements using an expressive syntax. Internally nested for-loops are created and compiled that generate the list.
Usage
gen_list(element_expr, ..., .compile = TRUE, .env = parent.frame())
Arguments
element_expr |
an expression that will be collected |
... |
either a logical expression that returns a length 1 result. A named list of equal length sequences that are iterated over in parallel or a named parameter with an iterable sequence. |
.compile |
compile the resulting for loop to bytecode befor eval |
.env |
the parent environment in which all the elements are being evaluated. |
Details
For parallel iterations all elements in the list need to be of
equal length. This is not checked at runtime at the moment.
Value
A list of all generated values. The element-type is determined by the
parameter element_expr.
Examples
gen_list(c(x, y), x = 1:10, y = 1:10, x + y == 10, x < y)
z <- 10
gen_list(c(x, y), x = 1:10, y = 1:10, x + y == !!z, x < y)
# it is also possible to iterate in parallel by passing a list of
# sequences
gen_list(c(x, y), list(x = 1:10, y = 1:10), (x + y) %in% c(4, 6))