Doc Forms (Typed Comments)

The Fold uses (doc ...) forms for searchable, introspectable annotations that survive in source code.

Basic Syntax

Contextual (belongs to enclosing definition)

scheme

(define (add x y)
  (doc 'type (-> Int Int Int))
  (doc 'description "Adds two numbers")
  (+ x y))

Targeted (names what it documents)

scheme

(doc factorial 'type (-> Int Int))
(define (factorial n)
  (if (= n 0) 1 (* n (factorial (- n 1)))))

Semantics

Property	Behavior
Arguments	NOT evaluated (pure metadata)
Return value	`void` — use in sequences, not value positions
Normalization	Stripped — code with/without docs hashes identically
Extraction	Tooling reads from source (`lf-todo`, `lf-types`)
Type authority	Authoritative — `(doc f 'type ...)` takes precedence over inference

Standard Tags

Tag	Purpose	Example
`'type`	Type signature	`(doc 'type (-> Int Int))`
`'description`	Human-readable description	`(doc 'description "Adds two numbers")`
`'param`	Parameter documentation	`(doc 'param 'x "The first operand")`
`'returns`	Return value description	`(doc 'returns "The sum")`
`'todo`	Work to be done	`(doc 'todo "Optimize for large inputs")`
`'fixme`	Known issue	`(doc 'fixme "Edge case with negative numbers")`
`'deprecated`	Deprecation notice	`(doc 'deprecated "Use add-safe instead")`
`'since`	Version introduced	`(doc 'since "1.2.0")`
`'see`	Related items	`(doc 'see 'subtract)`
`'note`	Implementation note	`(doc 'note "Uses memoization internally")`

Search Commands

After loading lattice/meta/docs.ss:

scheme

(lf-todo)           ; Find all todos in codebase
(lf-types)          ; Find all type annotations
(docs-for 'symbol)  ; Find docs for specific target
(doc-stats)         ; Count docs by tag

Type Checker Integration

Doc type annotations integrate with both the LSP and type inference:

Component	Behavior
LSP hover	Shows doc-declared types with highest priority
Type inference	Uses declared types via `lookup-declared-type` in `core/types/infer.ss`
Bridge	`load-doc-types-into-checker!` populates type checker from doc index

Example: Declaring Types for Inference

scheme

;; The type checker will trust this annotation
(doc my-complex-fn 'type (-> (List Int) (Maybe Int)))
(define (my-complex-fn lst)
  ;; Complex implementation...
  )

Todos vs BBS Issues

Use Case	When to Use
`(doc 'todo ...)`	Colocated with code, for localized improvements (performance, refactoring, cleanup)
BBS issue	Tracked work items, features, bugs, cross-cutting concerns, things needing scheduling

Rule of thumb: If it needs to be scheduled or tracked across sessions, use BBS. If it's a note-to-self next to the code, use (doc 'todo ...).

Examples

Full Function Documentation

scheme

(define (binary-search vec target)
  (doc 'type (-> (Vector Int) Int (Maybe Int)))
  (doc 'description "Binary search for target in sorted vector")
  (doc 'param 'vec "Sorted vector of integers")
  (doc 'param 'target "Value to find")
  (doc 'returns "Index wrapped in Just, or Nothing if not found")
  (doc 'todo "Add bounds checking")
  ;; implementation...
  )

Deprecation

scheme

(doc old-api 'deprecated "Use new-api instead. Will be removed in 2.0")
(define (old-api x) (new-api x))

Module-Level Documentation

scheme

;; At top of file
(doc 'description "Matrix operations for linear algebra")
(doc 'since "1.0.0")
(doc 'see 'linalg/vec)