Monad Summary

Monad Concept

• Container type with specific behavior rules
• Supports sequential operations
• Maintains computational context
• Example:

  interface Monad<T> {
    <U> Monad<U> flatMap(Transformer<? super T, 
        ? extends Monad<? extends U>> transformer);
  
    static <T> Monad<T> of(T value);
  }
  

Monad Laws

1. Left Identity:

   Monad.of(x).flatMap(f) == f.transform(x)
   

2. Right Identity:

   monad.flatMap(x -> Monad.of(x)) == monad
   

3. Associativity:

   monad.flatMap(f).flatMap(g) == 
     monad.flatMap(x -> f.transform(x).flatMap(g))
   

Examples of Monads

1. Maybe Monad:

   Maybe<Integer> result = Maybe.some(4)
       .flatMap(x -> Maybe.some(x + 1))
       .flatMap(x -> Maybe.some(x * 2));
   

2. Lazy Monad:

   Lazy<Integer> result = Lazy.of(() -> compute())
       .flatMap(x -> Lazy.of(() -> x + 1));
   

3. Loggable Monad:

   Loggable<Integer> result = Loggable.of(4)
       .flatMap(x -> new Loggable<>(x + 1, "Added 1"));
   

Benefits of Monads

1. Composition:

   • Chain operations
   • Maintain context
   • Handle side effects

2. Abstraction:

   • Hide implementation details
   • Consistent interface
   • Reusable patterns

3. Safety:

   • Type safety
   • Controlled effects
   • Predictable behavior

Best Practices

• Follow monad laws
• Document behavior
• Use meaningful names
• Keep operations pure
• Handle edge cases
• Test all paths