functionals (version 0.5.0)

freduce: Functional reduce

Description

Apply a binary function iteratively over a list or vector, reducing it to a single value or a sequence of intermediate results. This is a wrapper around [Reduce()] that supports optional initial values, right-to-left evaluation, accumulation of intermediate steps, and output simplification.

Usage

freduce(
  .x,
  .f,
  .init = NULL,
  .right = FALSE,
  .accumulate = FALSE,
  .simplify = TRUE
)

Value

A single value (default) or a list/vector of intermediate results if `.accumulate = TRUE`.

Arguments

.x

A vector or list to reduce.

.f

A binary function to apply. Can be given as a function or quoted (e.g., `\`+\``).

.init

Optional initial value passed to [Reduce()]. If `NULL`, reduction starts from the first two elements.

.right

Logical. If `TRUE`, reduction is performed from right to left.

.accumulate

Logical. If `TRUE`, returns a list of intermediate results (like a scan).

.simplify

Logical. If `TRUE` and all intermediate results are length 1, the output is simplified to a vector.

Examples

freduce(1:5, `+`)                          # => 15
freduce(letters[1:4], paste0)             # => "abcd"
freduce(list(1, 2, 3), `*`)               # => 6
freduce(1:3, `+`, .init = 10)             # => 16
freduce(1:3, paste0, .right = TRUE)       # => "321"
freduce(1:4, `+`, .accumulate = TRUE)     # => c(1, 3, 6, 10)