String Interpolation

String interpolation provides convenient inline expression evaluation within string literals.

Syntax

String interpolation uses ${} syntax:

let name = "Alice"
let age = 30
let message = "Hello ${name}, you are ${age} years old"

Expression Support

Any expression can be interpolated:

let x = 10
let y = 5
print("Sum: ${x + y}")
print("Product: ${x * y}")
print("Complex: ${(x + y) * 2 - 1}")

// Function calls
fn double(n) = n * 2
print("Doubled: ${double(5)}")

// Field access
type Person = { name: string, age: int }
let person = Person { name: "Bob", age: 25 }
print("Person: ${person.name}, age ${person.age}")

Type Handling

Interpolated expressions are automatically converted to strings:

• Primitive types: int, float, bool converted directly
• String types: Inserted as-is
• Result types: interpolation auto-unwraps — the success payload is rendered (context 5 of Result Auto-Unwrapping); an Error renders as Error(<message>), preserving the payload per ERR-PAYLOAD. To render the wrapper of a success, use toString.
• Complex types: Use toString() for explicit conversion

let num = 42
let flag = true
print("Number: ${num}, Flag: ${flag}")

let result = 10 + 5
print("Result: ${result}")        // "Result: 15"  (auto-unwrapped)
print(toString(result))           // "Success(15)" (wrapper kept)

Escaping

Use backslash to escape special characters:

let literal = "Dollar sign: \${not interpolated}"
let newline = "Line 1\nLine 2"
let quote = "He said \"Hello\""
let backslash = "Path: C:\\Users\\Name"

Supported escape sequences:

• \n - Newline
• \t - Tab
• \r - Carriage return
• \\ - Backslash
• \" - Double quote
• \${ - Literal ${ (prevents interpolation)