conditional.js

// Ideas
//-- note (() -> IO), random function
//-- Maybe denote it with a lambda instead

//+ given :: (a -> Bool) -> (() -> IO) -> Maybe IO

//+ ifthen :: (a -> Bool) -> (() -> IO) -> Maybe IO
function ifthen(predicate, action) {
  if (predicate()) {
    action();
  }
}

//-- Alias ------------------------------------------------------------
//+ given :: (a -> Bool) -> (() -> IO) -> Maybe IO
var given = ifthen;
//+ when :: (a -> Bool) -> (() -> IO) -> Maybe IO
var when = ifthen;

//+ ifelse :: (a -> Bool) -> (() -> IO) -> (() -> IO) -> Maybe IO
function ifelse(predicate, if_action, else_action) {
  if (predicate()) {
    if_action();
  } else {
    else_action();
  }
}

//-- Examples ---------------------------------------------------------
ifthen(isLoggedIn, welcome);
given(isLoggedIn, welcome);
when(loggedIn, welcome);

//-- Make it polymorphic? With optional else path
given(isLoggedIn, welcome, signup);

ifelse(isLoggedIn, welcome, signup);