#!/bin/bash
# your code goes here

rc() {
    return ${1:-1}
}

false
rc1=$?

true
rc2=$?

if rc $rc1 ; then
  echo false = true: $rc1
else
  echo false = false: $rc1
fi

if rc $rc2 ; then
  echo true = true: $rc2
else
  echo true = false: $rc2
fi

if rc "" ; then
  echo void = true
else
  echo void = false
fi

if rc ; then
  echo undef = true
else
  echo undef = false
fi