Name: Scope in Reason
Uploaded: 2018-03-19T09:50:19-05:00
Description: Reason has lexical scope. In this lesson we explore what this means for the visibility of bindings using local block scopes.

Course Overview: Get started with Reason

Setting up reason-cli, first Steps with rtop and Editor Support in Reason

Basic Datatypes and Operators in Reason

Let bindings, Type Inference and Type Aliases in Reason

Scope in Reason

if-else and Switch Expressions in Reason

Records and Objects in Reason

Variants and Pattern Matching Variants using switch in Reason

Elminate Illegal States in Reason with Variants

Using Reason's Type option

Declare Functions in Reason

Chain Functions using the pipe/reverse-application Operator in Reason

Recursive Functions in Reason

Tuples, Lists and Arrays in Reason

Reference Equality vs Structural (deep) Equality

Pattern Matching using switch in Reason

Type Parameters in Reason

Mutable let bindings in Reason

Exceptions in Reason

Imperative Loops (for & while) in Reason

Modules in Reason

First steps using Reason with BuckleScript

Get Started with Reason

Reason has lexical scope. In this lesson we explore what this means for the visibility of bindings using local block scopes.

https://app.egghead.io/api/v1/lessons/reason-scope-in-reason/subtitles

Instructor: [00:00] Reason has lexical scoping. Don't worry in case you aren't familiar with this term, as in this lesson, I will guide you through the relevant implications.

[00:09] First, we create the local scope using curly braces. It can contain one or multiple imperative statements, while the last one will automatically be returned. In this case, the value of the scope is the same as if we would type 42.

[00:29] Inside a scope, we can access bindings outside of its current scope, but let bindings defined inside a scope aren't accessible from the outside. In fact, we can shadow a let binding inside a scope, and it won't affect the let bindings outside of this local scope, even with different types.

[00:53] Here, we bind the string Hello to the name foo. Then we create the scope where we bind the integer two to the name foo again. If you refer to foo outside of the block, it's still Hello. Since every block returns the last statement as an expression, we can also bind the result to a name.

[01:25] In the coming lessons, we will see blocks being used many times to create a local scope for constructs like switch expressions or function definitions. Keep in mind, every time curly braces are used in Reason, it's the same scoping behavior.

Scope in Reason

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Get Started with Reason