Source files#

Each Manuscript source file ends in .ms and is a module. Put imports, type declarations, implementations, named functions, constants, and tests at the top level. Put executable statements and local let or var bindings inside a function or test. There is no separate module declaration or top-level initializer; a top-level let is a constant , not a statement.

The following src/greeting.ms file defines a customer and a function that creates a greeting. Read it from top to bottom:

export type Customer:
    name: String
    active: Bool

export fn welcome(customer: Customer) -> String:
    if customer.active:
        return "Welcome, {customer.name}!"

    return "Your account is inactive."

Blocks and layout#

Indentation defines blocks. Indented suites require exactly four additional spaces at each nesting level, and the formatter preserves that rule. Tabs in code and semicolons are rejected. Blank and comment-only lines do not change a block. The fields belong to Customer because they are indented under its declaration. The first return belongs to the if block; the second belongs directly to the function body.

Function and constructor calls accept positional arguments, optional labels, and mixtures of both. Matching-name shorthand remains available, such as reduce(amount, deduction). See declarations and calls for the call rules.

Expressions inside parentheses, brackets, or braces can span lines. This lets a call list its arguments on separate lines without changing their evaluation order:

let customer = Customer(
    name: "Ada",
    active: true,
)

Comments outside text literals begin with # and continue through the physical line. Identifiers use ASCII letters, digits, and underscores; text and comments may contain Unicode. Source is UTF-8, and names are case-sensitive.

# A local binding can infer its type from the value.
let count = 3

Module boundaries#

The resolved path of src/greeting.ms identifies its module. export makes a declaration available outside that module. Another file in src can import its customer type with:

import Customer from "./greeting.ms"

Relative imports resolve from the importing file’s directory. A project-root ms.toml configures the source directory, entry file, and optional import aliases. The rules for imports, visibility, and dependency cycles are in modules and capabilities ; see project configuration for path resolution.

The normative grammar defines accepted tokens, declarations, indentation, and anonymous-function suites. Expressions and operators defines precedence, operand types, and evaluation order. The local binding examples above are function-body fragments.

Continue with bindings , records , and function declarations to understand each declaration in the example.

See the grammar reference for exact syntax.