Closure simple example in selected technical computing languages. NOTE: performance checks are recommended, particularly in Julia and Python. In R on the other hand functional programming is nearly-native, and does not seem to slow down already slow code.

FP_closure.jl

power(expon) = x -> x^expon

square = power(2)
square(2)

cube = power(3)
cube(2)

FP_closure.py

def power(exponent):
  return (lambda x: x**exponent)

square = power(2)
square(2)

cube = power(3)
cube(2)

FP_closure.r

power <- function(exponent) {
  return (function(x) x^exponent)
}

square <- power(2)
square(2)

cube <- power(3)
cube(2)

## NOTE also useful double arrow assignment <<- in R
##  http://stackoverflow.com/questions/2628621/how-do-you-use-scoping-assignment-in-r