Typed data

Touba checks data at program boundaries: inputs, tool results and agent decisions. The compiler, runtime and model schemas use the same contracts.

Dates and lists

Date is an ISO calendar date without a time or timezone. date("2026-10-21") constructs a valid date; date("2026-02-30") is refused. Model results must already use the declared format.

Lists use [a, b]. An expected type allows an empty list, for example bind items as List of Text = [].

Field contracts

module examples.typed_data

type Invoice
    reference is Text length 1..40
    issued_on is Date
    currency is Text length 3 default "CAD"
    total_cents is Int min 0
    tags is List of Text length 0..8 default []
    reason is Optional of Text default none(Text)

function Draft
    gives Invoice
    do
        give record Invoice { reference as "INV-42", issued_on as date("2026-10-21"), total_cents as 12500 }

function Flag
    takes invoice as Invoice
    gives Invoice
    do
        give copy invoice { tags as ["review"], reason as some("Purchase order date needs review") }

Types describe accepted values. Business rules, such as comparing an invoice date with its purchase order date, belong in functions or strategies.

Element	Purpose
length 1..40	Inclusive bounds, in Unicode code points or list items
min, max	Numeric bounds
format "digits"	ASCII digits in a Text field
default	Value supplied by a source constructor when the field is omitted
copy	New record with explicit field replacements

Defaults do not repair external data. Handlers and models produce every field, including the explicit {"present": false} representation of an absent optional.

Approval result

human.approve … into approval binds an Approval value.

Field	Type	Content
decision	Text	approved, rejected or expired, according to the branch
subject_ref	Optional of Text	Attested signer, when present
attested_roles	List of Text	Roles verified by the host
request_id, run_id	Text	Correlation identifiers
accepted_at	Text	UTC ISO timestamp
comment	Optional of Text	Decision comment, up to 4,096 characters

Unknown fields are reported at compilation. Use the result for notifications and business statuses. Approval authority remains in private runtime receipts and host attestation.

Continue with typed data and role-based approvals.

Constants and diagnostics

A fixed date can be declared at module level. Comments may follow declarations and statements:

module examples.fixed_date

define Closing as Date = date("2026-10-31") # End of period

function ReadClosing
    gives Date
    do
        give Closing # Validated civil date

A constraint failure identifies its field, constraint and bound, for example min requires 0. The rejected value stays out of the diagnostic.

The Approval result also exposes comment as Optional of Text. This optional comment accompanies the decision; the host attests roles and signer identity.