purrr (version 0.2.2)

reduce: Reduce a list to a single value by iteratively applying a binary function.

Description

reduce combines from the left, reduce_right combines from the right.

Usage

reduce(.x, .f, ..., .init)
reduce_right(.x, .f, ..., .init)

Arguments

.x

A list or atomic vector.

.f

A two-argument function.

...

Additional arguments passed on to .f.

.init

If supplied, will be used as the first value to start the accumulation, rather than using x[[1]]. This is useful if you want to ensure that reduce returns the correct value when .x is is_empty().

Examples

1:3 %>% reduce(`+`)
1:10 %>% reduce(`*`)

5 %>%
  replicate(sample(10, 5), simplify = FALSE) %>%
  reduce(intersect)

x <- list(c(0, 1), c(2, 3), c(4, 5))
x %>% reduce(c)
x %>% reduce_right(c)
# Equivalent to:
x %>% rev() %>% reduce(c)

# Use init when you want reduce to return a consistent type when
# given an empty lists
list() %>% reduce(`+`)
list() %>% reduce(`+`, .init = 0)