force {base} | R Documentation

## Force evaluation of an Argument

### Description

Forces the evaluation of a function argument.

### Usage

    force(x)

### Arguments

`x` | a formal argument.

### Details

`force` forces the evaluation of a formal argument. This can be useful if the argument will be captured in a closure by the lexical scoping rules and will later be altered by an explicit assignment or an implicit assignment in a loop or an apply function.

### Note

`force` does not force the evaluation of promises.

### Examples

    f <- function(y) function() y
    lf <- vector("list", 5)
    for (i in seq(along = lf)) lf[[i]] <- f(i)
    lf[[1]]()  # returns 5

    g <- function(y) { force(y); function() y }
    lg <- vector("list", 5)
    for (i in seq(along = lg)) lg[[i]] <- g(i)
    lg[[1]]()  # returns 1

[Package base version 2.3.1 Index]