Is it feasible to implement anonymous functions in bash (even using eval, if necessary)?

Question

As bash doesn't have first class functions, I'm simulating anonymous functions by passing a string to a function, which then gets evaluated by eval.

it() {
    echo "$1" # prints the description of the spec
    beforeEach # a setup function
    eval "$2"

    if (($? == 0)); then
        # do something
    fi

    afterEach  # a cleanup function
}

it "should echo something" '{
  echo "something"
}'

This allows to write very concise tests (it defines a specification). Now I wonder if this is a valid use of eval.

EDIT

I am aware that the opening { and closing } are not need in the anonymous function string, it's just that that way it resembles for something like Jasmine.

EDIT

The pseudo anonymous function is actually a test, which means at the end of the test, there is something like

[[ var == 'foo' ]]

or

((i > 10))

i.e. some sort of test (or assert, in XUnit terms). It never needs to return anything than the return code which then gets evaluated, and if the return code is 0 (success), the description is printed in green, otherwise red (the test failed).

Answer 1

For one-time-use "anonymous" functions, I use the following convention to execute bash scripts in a function scope:

#!/usr/bin/env bash
_() {
  #...
} && _ "$@"
unset -f _

Although not truly anonymous, this is similar to the IIFE (Immediately-Invoked Function Expression) idiom in JavaScript.

Bash functions must have a name. You can use any name you like (main is a popular choice.) I prefer a single underscore _ because a) it's short and b) it's conventionally used in many languages to indicate a throwaway value.

Answer 2

I don't think it is a valid case for eval. Anonymous functions are useful in a few cases: closures, Currying, and callbacks come to mind (alliteration unintended). This implementation gives you none of those powers, since your eval'ed pseudo-functions still can't return a value (other than a 0-255 exit status), and definitely can't return another anonymous function.