Chapter: A first look at ReasonML’s syntax

[rauschma]

http://reasonmlhub.com/exploring-reasonml/ch_syntax-overview.html

[nhducit]

type tree('a) =
  | Empty
  | Node('a, tree('a), tree('a));

I come from JS. what is 'a mean? Can you explain it?

[rauschma]

tree is a variant, 'a is a type variable (similar to a generic class Tree<A> in Java). Explained here: http://reasonmlhub.com/exploring-reasonml/ch_variants.html

The point of the example was to give a first taste of the syntax. No worries if you don’t understand it (yet)! I’ll clarify that in the text.

[approots]

For me, it's too early in the book to introduce that concept. I'm likely to write-off Reason as too complex for now.

[nhducit]

I mean at least we should mention it, and point to the explanation in further chapter

[dp-1a]

Probably a typo in the code example in the chapter "Most things are expressions"?

let myBool = true; /* should be myBook? */
let print(if (myBook) "yes" else "no");

[rauschma]

@dp-1a “myBook” is the typo. It’ll be fixed in the next release. Thanks!

[craigglennie]

ReasonML is based on OCaml, which uses snake-casing for lowercase names (create_resource) and camel-casing for uppercase names (StringUtilities).

That’s why you’ll occasionally see camel-cased names. But all new ReasonML code is camel-cased (StringUtilities, createResource).

I think "That’s why you’ll occasionally see camel-cased names" should be "That’s why you’ll occasionally see snake-cased names"?

[rauschma]

@approots @nhducit Thanks for your feedback! I’ve updated the chapter: http://reasonmlhub.com/exploring-reasonml/ch_syntax-overview.html

[rauschma]

@craigglennie True! It’ll be fixed in the next release. Thanks!

[bhongy]

I'm going through the book and found it's very easy to digest and concise. Thank you for writing it!

Possibly typo in one of the examples on this page (won't compile):

/* A function that switches over a variant type */
let stringOfColor(c: color) =>
  switch (c) {
  | Red => "Red"
  | Green => "Green"
  | Blue => "Blue"
  };

Should the line with let binding be?:

let stringOfColor = (c: color) =>

[idkjs]

Probably a typo in the code example in the chapter "Most things are expressions"?

let myBool = true; let print = if (myBool) {"yes"} else {"no"}; / print = /

[rauschma]

@bhongy & @idkjs: Those were typos and are fixed now. Thanks for the feedback!

[mars0i]

There are many Initial_uppercase_and_then_snake module names in OCaml.

I don't think of x' in math or OCaml as meaning "changed x". I think of it as nothing more than "another x".

Thanks for making the book available online!

[osenvosem]

This syntax at the end of the chapter seems to be deprecated:

let len(arr: array('a)) = Array.length(arr);

refmt changes it to:

let len = (arr: array('a)) => Array.length(arr);

rtop accepts and executes it, though.

[rauschma]

@osenvosem Good catch! Fixed now, thanks.