closure in bash ... ?

closure_pattern

# closure - defined by Peter Landin in 1964
# closure - a function, plus a pointer to that functions scope

# In programming languages, closures (also lexical closures or function closures) are a technique for 
# implementing lexically scoped name binding in languages with first-class functions.  Duh.

# Operationally, a closure is a record storing a function[a] together with an environment:[1] 

# A mapping associating each free variable of the function (variables that are used locally, but defined in an enclosing scope) 
# with the value or storage location to which the name was bound when the closure was created. 

# A closure—unlike a plain function—allows the function to access those captured variables through the closure's reference to them, 
# even when the function is invoked outside their scope.  

# a closure may occur when a function is defined within another function, 
# and the inner function refers to local variables of the outer function.

# Closures: In Bash, functions themselves are always global (have "file scope"), so no closures.
# Function definitions may be nested, but these are not closures, though they look very much the same. 
# Functions are not "passable" (first-class), and there are no anonymous functions (lambdas). 
# In fact, nothing is "passable", especially not arrays.
# Bash uses strictly call-by-value semantics (magic alias hack excepted).

####
# Example 1
####
declare -x OUTER_FUNC_RESULT=Outer_Function() {
  local a=1
  
  local inner_result=Inner_Function() {
    alert(a)
  }
  return inner_result
}

fnc="$(OUTER_FUNC_RESULT)"
echo "$fnc"

####
# Example 2
####
var f, g;
function foo() {
  var x;
  f = function() { return ++x; };
  g = function() { return --x; };
  x = 1;
  alert('inside foo, call to f(): ' + f()); // "2"
}
foo();
alert('call to g(): ' + g()); // "1"
alert('call to f(): ' + f()); // "2"

##########

Nice, I've just accidentally came up with something like this:
https://gist.github.com/pinkeen/287ad64d951f7bf138afce975d3bce7b