listcomp (version 0.4.1)

gen_list: 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.

Value

A list of all generated values. The element-type is determined by the parameter element_expr.

Details

For parallel iterations all elements in the list need to be of equal length. This is not checked at runtime at the moment.

Examples

# NOT RUN {
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))

# }