base (version 3.6.0)

callCC: Call With Current Continuation

Description

A downward-only version of Scheme's call with current continuation.

Usage

callCC(fun)

Arguments

fun

function of one argument, the exit procedure.

Details

callCC provides a non-local exit mechanism that can be useful for early termination of a computation. callCC calls fun with one argument, an exit function. The exit function takes a single argument, the intended return value. If the body of fun calls the exit function then the call to callCC immediately returns, with the value supplied to the exit function as the value returned by callCC.

Examples

# NOT RUN {
# The following all return the value 1
callCC(function(k) 1)
callCC(function(k) k(1))
callCC(function(k) {k(1); 2})
callCC(function(k) repeat k(1))
# }