Variables

Declaration

All variables must be declared with let before use.

let city = "Manila"
let port = 8080
let active = true
let data = null        // explicitly null

Optional Type Annotation

A type annotation after : is accepted syntactically but is not enforced at runtime (the language is dynamic). It serves as documentation.

let zone: Subnet = 192.168.1.0/24
let count: Integer = 0

Re-assignment

After declaration, a variable is re-assigned without let:

let score = 0
score = score + 10   // re-assignment

Compound Assignment

Joa supports the common shorthand operators that combine an arithmetic operation with assignment:

let score = 10
score += 5     // 15
score *= 2     // 30
score -= 3     // 27
score /= 9     // 3 (integer division)
print(score)   // 3

Assignment Errors

Attempting to assign to a name that was never declared with let is a Name Error:

undeclared = 5
// ❌ Name Error: Cannot assign to undefined variable 'undeclared'.
// 💡 Hint: Declare the variable first with: let undeclared = ...