fpEs — API Reference

Complete export surface of fpes v1.2.0, generated from source introspection and verified by executing each module. Companion to OVERVIEW.md.

Stability legend:

supported — shown in the README.

leaked — exported, tested, and working, but README-silent (the author's own term; see commit 7a4afce "Add some leaked common functions"). Safe to use.

internal — implementation detail; do not depend on it.

How to read this doc

require('fpes') returns a flat namespace: Maybe, MonadIO, Publisher, plus every fp and pattern export spread to the top level. Subpath imports (fpes/maybe, fpes/fp, fpes/pattern, fpes/monadio, fpes/publisher) return that single module.

Curried functions accept arguments one group at a time; most also work fully applied.

Maybe (`fpes/maybe`)

Maybe is a singleton instance of an internal MaybeDef class. None is the shared empty value. Some is any present value. Fantasy Land aliases live on the prototype (Maybe only).

Static / constructor

Symbol	Kind	Stability	Summary
`of(ref)` / `just(ref)`	fn	supported	Wrap a value; `null`/`undefined` → `None`.
`fromFalsy(ref)`	fn	leaked	Falsy (`0`,`''`,`false`,`null`) → `None`, else `Some`.
`fromPredicate(pred, val)`	fn	leaked	`Some(val)` if `pred(val)`, else `None`; curries on 1 arg.
`empty()` / `zero()`	fn	leaked	Return `None` (Fantasy Land monoid/plus identity).

Instance methods

Symbol	Kind	Stability	Summary
`isPresent()` / `isNull()`	fn	supported	Presence test.
`unwrap()` / `extract()`	fn	supported / leaked	Get the raw value (`None` → `null`).
`map(fn)` / `then(fn)`	fn	supported	Transform the value (`None` short-circuits).
`flatMap(fn)` / `chain(fn)` / `bind(fn)`	fn	supported / leaked	Monadic bind; `fn` returns a `Maybe`.
`or(ref)` / `alt(m)`	fn	supported / leaked	Fallback value on `None` only (no-op on `Some`).
`orDo(fn)`	fn	supported	Lazy fallback on `None` (runs `fn()`).
`letDo(fn)` / `extend(fn)`	fn	supported / leaked	Map on `Some` (no-op on `None`).
`filter(pred)`	fn	leaked	Keep value if `pred` holds, else `None`.
`reduce(reducer, init)`	fn	leaked	`reducer(init, value)`; `None` → `init`.
`join()`	fn	leaked	Flatten a nested `Maybe`.
`ap(maybeFn)`	fn	leaked	Applicative — FL order: `value.ap(Maybe.of(fn))`.
`chainRec(f, i)`	fn	leaked	Stack-safe recursive chain (trampolined).
`equals(m)`	fn	leaked	Value equality (SameValueZero; `NaN` equals `NaN`).
`toList()`	fn	leaked	`[value]` for `Some`, `[]` for `None`.
`toString()`	fn	leaked	`Some(<json>)` or `None`.
`fantasy-land/*`	fn	leaked	Fantasy Land aliases: `of`,`empty`,`zero`,`map`,`ap`,`chain`,`join`,`alt`,`extend`,`extract`,`equals`,`reduce`,`filter`.
`ref`	field	internal	The wrapped value. Do not read directly.

MonadIO (`fpes/monadio`)

A lazy IO monad. Effects are stored and only run on subscribe.

Static

Symbol	Kind	Stability	Summary
`of(ref)` / `just(ref)`	fn	supported	Wrap a value as a pure effect.
`doM(genFn)`	fn	supported	Do-notation: run a generator, awaiting yielded Promise/MonadIO/Maybe. Returns a Promise.
`promiseof(ref)`	fn	supported	`Promise.resolve(ref)`.
`fromPromise(p)`	fn	leaked	Lift a Promise into a `MonadIO`.
`generatorToPromise(genFn)`	fn	leaked	Like `doM` but always returns a Promise.
`wrapGenerator(genFn)`	fn	internal	Step engine behind `doM`.

Instance methods

Symbol	Kind	Stability	Summary
`map(fn)` / `then(fn)`	fn	supported	Transform the eventual value (lazy).
`flatMap(fn)` / `chain(fn)`	fn	supported / leaked	Bind; `fn` returns a `MonadIO`.
`bind(fn)`	fn	leaked	Alias of `then`.
`ap(monadFn)`	fn	leaked	Applicative apply.
`subscribe(fn, async?)`	fn	supported	Runs the effect; `async === true` schedules via Promise.
`effect`	field	internal	The stored thunk. Do not read directly.

Publisher (`fpes/publisher`)

A minimal PubSub / observable event bus.

Symbol	Kind	Stability	Summary
`new Publisher()`	ctor	supported	Create a bus.
`subscribe(fn)`	fn	supported	Register a handler (deduped); returns `fn`.
`unsubscribe(fn)`	fn	supported	Remove a handler.
`publish(value, async?)`	fn	supported	Emit to all handlers; `async === true` schedules via Promise.
`map(fn)`	fn	supported	Return a derived `Publisher` of mapped values.
`clear()`	fn	leaked	Remove all handlers.
`subscribers` / `origin`	field	internal	Handler list / upstream link. Do not depend on.

fp (`fpes/fp`)

Ramda/Lodash-style utilities. All 59 are public API; only compose, curry, map appear in the README — the other 56 are "leaked" (working, tested, undocumented).

Function & composition

Symbol	Curried	Stability	Summary
`compose(...fns)`	–	supported	Right-to-left composition.
`pipe(...fns)`	–	leaked	Left-to-right composition.
`curry(fn)`	–	supported	Curry by arity (rest params count as 0).
`partial(fn, ...pre)`	yes	leaked	Bind leading args.
`partialRight(fn, ...pre)`	yes	leaked	Bind trailing args.
`partialProps(fn, preObj, lateObj)`	yes	leaked	Merge preset + later prop objects.
`unary(fn, arg)`	yes	leaked	Call `fn` with a single arg.
`spread(fn, args)`	yes	leaked	Apply an array as args.
`gather(fn, ...args)`	yes	leaked	Collect args into one array param.
`not(fn, ...args)`	yes*	leaked	`!fn(...args)` — *fires immediately for `not(fn)` (see gotchas).
`ifelse(test, elseF, fn)`	yes	leaked	Branch on `test()`.
`when(test, fn)`	yes	leaked	`fn()` if `test()` else `undefined`.
`trampoline(fn)`	–	leaked	Stack-safe recursion (loop while result is a fn).
`memoize(fn)`	–	leaked	Cache results by args (see gotchas re: key collisions).
`debounce(fn, ms)`	yes	leaked	`{ ref, cancel }` around `setTimeout`.
`schedule(fn, ms)`	yes	leaked	`{ ref, cancel }` around `setInterval`.
`snooze(ms)`	–	leaked	`Promise` that resolves after `ms`.

Collection & iteration

Symbol	Curried	Stability	Summary
`map(fn, list)`	yes	supported	Map.
`filter(fn, list)`	yes	leaked	Filter.
`reduce(fn, init, ...list)`	yes	leaked	Left fold (variadic list).
`foldl(fn, init, list)`	yes	leaked	Left fold.
`foldr(fn, init, list)`	yes	leaked	Right fold.
`flatten(list)`	–	leaked	One-level flatten.
`flattenMap(fn, list)`	yes	leaked	Map then flatten.
`range(n)`	–	leaked	`[0..n-1]`.
`chunk(list, size)`	yes	leaked	Split into size-`n` chunks.
`take(n, list)`	yes	leaked	First `n` (immutable).
`drop(list, n, dir?, fn?)`	manual	leaked	Drop `n` from left/right, optional filter.
`head(list)`	–	leaked	First element (`[]` if empty).
`tail(list)`	–	leaked	All but first.
`initial(list)`	–	leaked	All but last.
`shift(list)`	–	leaked	First element (non-mutating).
`nth(list, i)`	manual	leaked	Index; negative is mirror-flipped (see gotchas).
`reverse(list)`	–	leaked	Reverse array or string.
`unique(list)`	–	leaked	Dedupe (first-seen order).
`sortedUniq(list)`	–	leaked	Dedupe + sort (numeric-aware).
`sortedIndex(list, val, pos?)`	manual	leaked	Insertion index for a value.
`contains(list, val)`	–	leaked	Membership test.
`find(fn, list)`	yes	leaked	First match.
`findLast(fn, list)`	yes	leaked	Last match.
`findIndex(fn, list)`	yes	leaked	Index of first match (`-1` if none).
`findLastIndex(fn, list)`	yes	leaked	Index of last match (`-1` if none).
`fill(list, val, start?, end?)`	manual	leaked	Fill range with a value (immutable).
`compact(list, typ?)`	manual	leaked	Drop falsy (or keep by `typeof typ`).
`pull(list, ...vals)`	manual	leaked	Remove given values.

Set operations & zips

Symbol	Curried	Stability	Summary
`concat(list, ...arrays)`	–	leaked	Concatenate arrays.
`union(a, b, dup?)`	manual	leaked	Union, optional duplicates.
`intersection(...arrays)`	–	leaked	Common values (main-ordered).
`difference(...arrays)`	–	leaked	In follower, not in main (deduped).
`differenceWithDup(...arrays)`	–	leaked	Difference keeping duplicates.
`zip(...lists)`	–	leaked	Zip parallel arrays.
`unzip(list)`	–	leaked	Inverse of `zip`.
`fromPairs(list)`	–	leaked	`[[k,v]]` → object.

Object / lens-ish

Symbol	Curried	Stability	Summary
`prop(key, obj)`	yes	leaked	Read a property.
`propEq(val, key, obj)`	yes	leaked	`obj[key] === val`.
`get(obj, key)`	yes	leaked	Property read (obj-first).
`matches(rule, obj)`	yes	leaked	Shallow object match.
`clone(obj)`	–	leaked	JSON deep clone (`undefined`/`NaN` pass through).

pattern (`fpes/pattern`)

Pattern matching and algebraic data types. 39 exports; 17 shown in README.

Matching entry points

Symbol	Kind	Stability	Summary
`either(value, ...patterns)`	fn	supported	Match `value`; runs first matching pattern's effect. Throws if none match and no `otherwise`.
`otherwise(effect)`	fn	supported	Catch-all pattern.
`PatternMatching`	class	supported*	Reusable matcher (name shown, usage sparse).
`Pattern`	class	internal	Raw `(matches, effect)` pair; prefer `inCaseOf*`.
`Matchable`	class	internal	Base class for types.

`inCaseOf*` guards

Symbol	Stability	Matches
`inCaseOfEqual(val, effect)`	supported	strict `===`
`inCaseOfClass(cls, effect)`	supported	`instanceof cls`
`inCaseOfObject(effect)`	supported	plain object (not array/null)
`inCaseOfNumber(effect)`	leaked	number (rejects boolean/array; accepts numeric strings)
`inCaseOfString(effect)`	leaked	`typeof === 'string'`
`inCaseOfNaN(effect)`	leaked	`NaN`/non-number
`inCaseOfArray(effect)`	leaked	`Array.isArray`
`inCaseOfNull(effect)`	leaked	`null`/`undefined`
`inCaseOfFunction(effect)`	leaked	`instanceof Function`
`inCaseOfRegex(regex, effect)`	leaked	regex test (restores `lastIndex` for `/g`,`/y`)
`inCaseOfPattern(effect)`	leaked	value is a `Pattern`
`inCaseOfPatternMatching(effect)`	leaked	value is a `PatternMatching`
`inCaseOfCompType(effect)`	leaked	value is a `CompType`
`inCaseOfCompTypeMatchesWithSpread(ct, effect)`	leaked	array-spread or direct comp-type match

`Type*` predicates (matcher objects)

Type* are the ()=>true forms of the guards, usable in ADT/comp-type composition.

Symbol	Stability	Summary
`TypeNumber` `TypeString` `TypeNaN` `TypeObject` `TypeArray` `TypeNull`	supported	Primitive matchers.
`TypeEqualTo(val)` `TypeClassOf(cls)` `TypeRegexMatches(rx)`	supported	Parameterized matchers.
`TypeFunction` `TypePattern` `TypePatternMatching` `TypeCompType`	leaked	Structural matchers.
`TypeInCaseOf(matches)`	leaked	Custom predicate matcher.
`TypeMatchesAllPatterns(...patterns)`	leaked	Conjunction (all must match).
`TypeCompTypeMatchesWithSpread(ct)`	leaked	Spread-aware comp-type matcher.
`TypeADT(adtDef)`	leaked	Match an object against a `{key: Type}` schema.

Algebraic data types

Symbol	Kind	Stability	Summary
`SumType(...types)`	class	supported	Tagged union — matches if any member matches.
`ProductType(...types)`	class	supported	Record/tuple — matches if all members match (positional).
`CompType`	class	supported	Base composite type (`apply`/`matches`).

Appendix: leaked / alias / Fantasy Land coverage

fp: 56 of 59 exports are undocumented in the README (all public, all tested).
Maybe: ~30 undocumented instance/static members, including 13 fantasy-land/* aliases and the short aliases chain/bind/alt/extend/extract.
pattern: 22 of 39 exports undocumented.
MonadIO: fromPromise, generatorToPromise undocumented; wrapGenerator is internal.
Publisher: clear undocumented.

Do not depend on (internal): Maybe.ref, MonadIO.effect, MonadIO.wrapGenerator, Publisher.subscribers, Publisher.origin, and the raw Pattern/Matchable classes.

Last verified: v1.2.0 (source introspection + runtime execution).

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fpEs — API Reference

How to read this doc

Maybe (`fpes/maybe`)

Static / constructor

Instance methods

MonadIO (`fpes/monadio`)

Static

Instance methods

Publisher (`fpes/publisher`)

fp (`fpes/fp`)

Function & composition

Collection & iteration

Set operations & zips

Object / lens-ish

pattern (`fpes/pattern`)

Matching entry points

`inCaseOf*` guards

`Type*` predicates (matcher objects)

Algebraic data types

Appendix: leaked / alias / Fantasy Land coverage

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fpEs — API Reference

How to read this doc

Maybe (fpes/maybe)

Static / constructor

Instance methods

MonadIO (fpes/monadio)

Static

Instance methods

Publisher (fpes/publisher)

fp (fpes/fp)

Function & composition

Collection & iteration

Set operations & zips

Object / lens-ish

pattern (fpes/pattern)

Matching entry points

inCaseOf* guards

Type* predicates (matcher objects)

Algebraic data types

Appendix: leaked / alias / Fantasy Land coverage

Maybe (`fpes/maybe`)

MonadIO (`fpes/monadio`)

Publisher (`fpes/publisher`)

fp (`fpes/fp`)

pattern (`fpes/pattern`)

`inCaseOf*` guards

`Type*` predicates (matcher objects)