Variables and Types

Overview

Variables in Echo are declared with explicit types, and those types are enforced at runtime.

Syntax

name: str = "Echo";
count: int = 1;
price: float = 2.5;
ok: bool = true;
value: dynamic = null;

Example

title: str = "Echo";
users: int = 42;
ratio: float = 1.5;
enabled: bool = true;
missing: dynamic = null;

say(title, users, ratio, enabled, missing);

Output

Echo 42 1.5 true null

Notes

Declaration

Use this form for a new variable:

name: Type = expression;

Reassignment

Use this form after declaration:

name = expression;

Built-in types

• int: whole numbers
• float: decimal numbers
• str: text
• bool: true or false
• dynamic: any runtime value
• list: mutable ordered collection
• hash: mutable key-value map
• null: literal value for missing data

Runtime type checking

count: int = 1;
count = 2;      // valid
count = "two"; // runtime type error

Common Mistakes

Assigning before declaration

count = 1;

Treating null as a type

x: null = null;

Use dynamic instead.

Using void as a variable type

This is not allowed.

Current Limitation

• No generics such as list<int>.
• Lists are not element-typed.
• Hashes are only structurally typed when used through object type aliases.

See Also

• Strings and Interpolation
• Lists
• Hashes
• Type Aliases