Problem Statement

Create a list of ten functions, in the simplest manner possible   (anonymous functions are encouraged),   such that the function at index   i   (you may choose to start   i   from either   0   or   1),   when run, should return the square of the index,   that is,   i 2. Display the result of running any but the last function, to demonstrate that the function indeed remembers its value.

Demonstrate how to create a series of independent closures based on the same template but maintain separate copies of the variable closed over. In imperative languages, one would generally use a loop with a mutable counter variable. For each function to maintain the correct number, it has to capture the value of the variable at the time it was created, rather than just a reference to the variable, which would have a different value by the time the function was run. See also: Multiple distinct objects

Let's start with the solution:

def power2
    dup *
enddef

getid power2 10 repeat

len for
    dup rot swap get rot swap exec print " " print
endfor

nl

/# Another mode #/
len for
    var i
    i get i swap exec print " " print
endfor