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0 pointsdmitriid8y ago0 comments

The entire "concept" of a monad fits in that description I linked to. It can be easily reused (which I've done numerous times with it, and with other concepts on that page).

Haskell for some reasons insists that I should only go for "The concept of a monad, which arises from category theory, has been applied by Moggi to structure the denotational semantics of programming languages" and

  A monad is a triple (M,unit,⋆) consisting of a type constructor M and two operations of the given 
  polymorphic types. These operations must satisfy three laws given in Section 3.
  
  We will often write expressions in the form
    m ⋆ λa. n

Should I? Really?

0 comments

mrkgnao8y ago

Yes, you should care about the laws!

They allow you to edit code without the aforementioned released-last-week test runner having to check all your code after a big refactor. I mean, you can't call something with a "flatMap" method and a "return" method a monad! There are tons of nonsensical definitions that fit that which are going to become very unpleasant to use quickly.

dmitriidOP8y ago

> They allow you to edit code without the aforementioned released-last-week test runner having to check all your code after a big refactor.

Oh wow. How did I ever live with big refactorings before?

> There are tons of nonsensical definitions that fit that which are going to become very unpleasant to use quickly.

I recently learned that, apparently, I've been using "monads" and "monadic composition" for years now, never knowing what it is. Can't remember any unpleasantness that would "quickly arise".

There are other things than blind following after a Platonic ideal.

mrkgnao8y ago

The unpleasantness arises when writing Monad instances that don't follow the laws. Setting your disingenuity aside, try using

  xs >>= f = concat (reverse (map f xs))

  Array.prototype.chain = function (f) {
    return reverse(this.reduce((acc, it) => acc.concat(f(it)), []))
  }

(I don't know how JS works, but you get it) instead of

    xs >>= f = concat (map f xs)

and enjoy refactoring your code, blissfully and consciously ignorant of the laws that make a monad a monad. The laws aren't just supposed to enrich the "life of the mind".

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0 pointsdmitriid8y ago0 comments

The entire "concept" of a monad fits in that description I linked to. It can be easily reused (which I've done numerous times with it, and with other concepts on that page).

  A monad is a triple (M,unit,⋆) consisting of a type constructor M and two operations of the given 
  polymorphic types. These operations must satisfy three laws given in Section 3.
  
  We will often write expressions in the form
    m ⋆ λa. n

Should I? Really?

0 comments

mrkgnao8y ago

Yes, you should care about the laws!

dmitriidOP8y ago

> They allow you to edit code without the aforementioned released-last-week test runner having to check all your code after a big refactor.

Oh wow. How did I ever live with big refactorings before?

> There are tons of nonsensical definitions that fit that which are going to become very unpleasant to use quickly.

I recently learned that, apparently, I've been using "monads" and "monadic composition" for years now, never knowing what it is. Can't remember any unpleasantness that would "quickly arise".

There are other things than blind following after a Platonic ideal.

mrkgnao8y ago

The unpleasantness arises when writing Monad instances that don't follow the laws. Setting your disingenuity aside, try using

  xs >>= f = concat (reverse (map f xs))

  Array.prototype.chain = function (f) {
    return reverse(this.reduce((acc, it) => acc.concat(f(it)), []))
  }

(I don't know how JS works, but you get it) instead of

    xs >>= f = concat (map f xs)

and enjoy refactoring your code, blissfully and consciously ignorant of the laws that make a monad a monad. The laws aren't just supposed to enrich the "life of the mind".

1 more reply

j / k navigate · click thread line to collapse