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/**
* The `Reader` monad (also called the Environment monad). Represents a computation, which can read values from a shared environment,
* pass values from function to function, and execute sub-computations in a modified environment.
* Using `Reader` monad for such computations is often clearer and easier than using the `State` monad.
*
* In this example the `Reader` monad provides access to variable bindings. `Bindings` are a map of `number` variables.
* The variable count contains number of variables in the bindings. You can see how to run a `Reader` monad and retrieve
* data from it, how to access the `Reader` data with `ask` and `asks`.
*
* @example
* import { pipe } from 'fp-ts/function'
* import * as O from 'fp-ts/Option'
* import * as R from 'fp-ts/Reader'
* import * as RR from 'fp-ts/ReadonlyRecord'
*
* interface Bindings extends RR.ReadonlyRecord<string, number> {}
*
* // The Reader monad, which implements this complicated check.
* const isCountCorrect: R.Reader<Bindings, boolean> = pipe(
* R.Do,
* R.bind('count', () => R.asks(lookupVar('count'))),
* R.bind('bindings', () => R.ask()),
* R.map(({ count, bindings }) => count === RR.size(bindings))
* )
*
* // The selector function to use with 'asks'.
* // Returns value of the variable with specified name.
* const lookupVar = (name: string) => (bindings: Bindings): number =>
* pipe(
* bindings,
* RR.lookup(name),
* O.getOrElse(() => 0)
* )
*
* const sampleBindings: Bindings = { count: 3, a: 1, b: 2 }
*
* assert.deepStrictEqual(isCountCorrect(sampleBindings), true)
*
* @since 2.0.0
*/
import { getApplicativeMonoid } from './Applicative';
import { apFirst as apFirst_, apS as apS_, apSecond as apSecond_, getApplySemigroup } from './Apply';
import * as chainable from './Chain';
import * as E from './Either';
import { constant, dual, flow, identity, pipe } from './function';
import { bindTo as bindTo_, flap as flap_, let as let__ } from './Functor';
import * as _ from './internal';
// -------------------------------------------------------------------------------------
// constructors
// -------------------------------------------------------------------------------------
/**
* Reads the current context
*
* @category constructors
* @since 2.0.0
*/
export var ask = function () { return identity; };
/**
* Projects a value from the global context in a Reader
*
* @category constructors
* @since 2.0.0
*/
export var asks = identity;
// -------------------------------------------------------------------------------------
// combinators
// -------------------------------------------------------------------------------------
/**
* Changes the value of the local context during the execution of the action `ma` (similar to `Contravariant`'s
* `contramap`).
*
* @example
* import { pipe } from 'fp-ts/function'
* import * as R from 'fp-ts/Reader'
* import * as string from 'fp-ts/string'
*
* const calculateContentLen: R.Reader<string, number> = pipe(
* R.Do,
* R.bind('content', () => R.ask<string>()),
* R.map(({ content }) => string.size(content))
* )
*
* // Calls calculateContentLen after adding a prefix to the Reader content.
* const calculateModifiedContentLen: R.Reader<string, number> = pipe(
* calculateContentLen,
* R.local((s) => 'Prefix ' + s)
* )
*
* const s = '12345'
*
* assert.deepStrictEqual(
* "Modified 's' length: " + calculateModifiedContentLen(s) + '\n' + "Original 's' length: " + calculateContentLen(s),
* "Modified 's' length: 12\nOriginal 's' length: 5"
* )
*
* @since 2.0.0
*/
export var local = function (f) { return function (ma) { return function (r2) {
return ma(f(r2));
}; }; };
/**
* Less strict version of [`asksReader`](#asksreader).
*
* The `W` suffix (short for **W**idening) means that the environment types will be merged.
*
* @category constructors
* @since 2.11.0
*/
export var asksReaderW = function (f) {
return function (r) {
return f(r)(r);
};
};
/**
* Effectfully accesses the environment.
*
* @category constructors
* @since 2.11.0
*/
export var asksReader = asksReaderW;
/* istanbul ignore next */
var _map = function (fa, f) { return pipe(fa, map(f)); };
/* istanbul ignore next */
var _ap = function (fab, fa) { return pipe(fab, ap(fa)); };
var _compose = function (bc, ab) { return pipe(bc, compose(ab)); };
var _promap = function (fea, f, g) { return pipe(fea, promap(f, g)); };
/**
* `map` can be used to turn functions `(a: A) => B` into functions `(fa: F<A>) => F<B>` whose argument and return types
* use the type constructor `F` to represent some computational context.
*
* @category mapping
* @since 2.0.0
*/
export var map = function (f) { return function (fa) { return function (r) { return f(fa(r)); }; }; };
/**
* Less strict version of [`ap`](#ap).
*
* The `W` suffix (short for **W**idening) means that the environment types will be merged.
*
* @since 2.8.0
*/
export var apW = function (fa) { return function (fab) { return function (r) {
return fab(r)(fa(r));
}; }; };
/**
* @since 2.0.0
*/
export var ap = apW;
/**
* @category constructors
* @since 2.0.0
*/
export var of = constant;
/**
* @category sequencing
* @since 2.14.0
*/
export var flatMap = /*#__PURE__*/ dual(2, function (ma, f) {
return function (r) {
return f(ma(r))(r);
};
});
/**
* Less strict version of [`flatten`](#flatten).
*
* The `W` suffix (short for **W**idening) means that the environment types will be merged.
*
* @category sequencing
* @since 2.11.0
*/
export var flattenW =
/*#__PURE__*/ flatMap(identity);
/**
* @category sequencing
* @since 2.0.0
*/
export var flatten = flattenW;
/**
* @since 2.0.0
*/
export var compose = function (ab) { return function (bc) { return flow(ab, bc); }; };
/**
* @since 2.0.0
*/
export var promap = function (f, g) { return function (fea) { return function (a) {
return g(fea(f(a)));
}; }; };
/**
* @category constructors
* @since 2.0.0
*/
export var id = function () { return identity; };
/**
* @since 2.10.0
*/
export var first = function (pab) {
return function (_a) {
var a = _a[0], c = _a[1];
return [pab(a), c];
};
};
/**
* @since 2.10.0
*/
export var second = function (pbc) {
return function (_a) {
var a = _a[0], b = _a[1];
return [a, pbc(b)];
};
};
/**
* @since 2.10.0
*/
export var left = function (pab) { return E.fold(function (a) { return _.left(pab(a)); }, E.right); };
/**
* @since 2.10.0
*/
export var right = function (pbc) { return E.fold(E.left, function (b) { return _.right(pbc(b)); }); };
/**
* @category type lambdas
* @since 2.0.0
*/
export var URI = 'Reader';
/**
* @category instances
* @since 2.7.0
*/
export var Functor = {
URI: URI,
map: _map
};
/**
* @category mapping
* @since 2.10.0
*/
export var flap = /*#__PURE__*/ flap_(Functor);
/**
* @category instances
* @since 2.10.0
*/
export var Pointed = {
URI: URI,
of: of
};
/**
* @category instances
* @since 2.10.0
*/
export var Apply = {
URI: URI,
map: _map,
ap: _ap
};
/**
* Combine two effectful actions, keeping only the result of the first.
*
* @since 2.0.0
*/
export var apFirst = /*#__PURE__*/ apFirst_(Apply);
/**
* Less strict version of [`apFirst`](#apfirst).
*
* The `W` suffix (short for **W**idening) means that the environment types will be merged.
*
* @since 2.12.0
*/
export var apFirstW = apFirst;
/**
* Combine two effectful actions, keeping only the result of the second.
*
* @since 2.0.0
*/
export var apSecond = /*#__PURE__*/ apSecond_(Apply);
/**
* Less strict version of [`apSecond`](#apsecond).
*
* The `W` suffix (short for **W**idening) means that the environment types will be merged.
*
* @since 2.12.0
*/
export var apSecondW = apSecond;
/**
* @category instances
* @since 2.7.0
*/
export var Applicative = {
URI: URI,
map: _map,
ap: _ap,
of: of
};
/**
* @category instances
* @since 2.10.0
*/
export var Chain = {
URI: URI,
map: _map,
ap: _ap,
chain: flatMap
};
/**
* @category instances
* @since 2.7.0
*/
export var Monad = {
URI: URI,
map: _map,
of: of,
ap: _ap,
chain: flatMap
};
/**
* Composes computations in sequence, using the return value of one computation to determine the next computation and
* keeping only the result of the first.
*
* @category combinators
* @since 2.15.0
*/
export var tap = /*#__PURE__*/ dual(2, chainable.tap(Chain));
/**
* @category instances
* @since 2.7.0
*/
export var Profunctor = {
URI: URI,
map: _map,
promap: _promap
};
/**
* @category instances
* @since 2.7.0
*/
export var Category = {
URI: URI,
compose: _compose,
id: id
};
/**
* @category instances
* @since 2.8.3
*/
export var Strong = {
URI: URI,
map: _map,
promap: _promap,
first: first,
second: second
};
/**
* @category instances
* @since 2.8.3
*/
export var Choice = {
URI: URI,
map: _map,
promap: _promap,
left: left,
right: right
};
// -------------------------------------------------------------------------------------
// do notation
// -------------------------------------------------------------------------------------
/**
* @category do notation
* @since 2.8.0
*/
export var bindTo = /*#__PURE__*/ bindTo_(Functor);
var let_ = /*#__PURE__*/ let__(Functor);
export {
/**
* @category do notation
* @since 2.13.0
*/
let_ as let };
/**
* @category do notation
* @since 2.8.0
*/
export var bind = /*#__PURE__*/ chainable.bind(Chain);
/**
* The `W` suffix (short for **W**idening) means that the environment types will be merged.
*
* @category do notation
* @since 2.8.0
*/
export var bindW = bind;
/**
* @category do notation
* @since 2.9.0
*/
export var Do = /*#__PURE__*/ of(_.emptyRecord);
/**
* @category do notation
* @since 2.8.0
*/
export var apS = /*#__PURE__*/ apS_(Apply);
/**
* Less strict version of [`apS`](#aps).
*
* The `W` suffix (short for **W**idening) means that the environment types will be merged.
*
* @category do notation
* @since 2.8.0
*/
export var apSW = apS;
/**
* @since 2.11.0
*/
export var ApT = /*#__PURE__*/ of(_.emptyReadonlyArray);
// -------------------------------------------------------------------------------------
// array utils
// -------------------------------------------------------------------------------------
/**
* Equivalent to `ReadonlyNonEmptyArray#traverseWithIndex(Applicative)`.
*
* @category traversing
* @since 2.11.0
*/
export var traverseReadonlyNonEmptyArrayWithIndex = function (f) {
return function (as) {
return function (r) {
var out = [f(0, _.head(as))(r)];
for (var i = 1; i < as.length; i++) {
out.push(f(i, as[i])(r));
}
return out;
};
};
};
/**
* Equivalent to `ReadonlyArray#traverseWithIndex(Applicative)`.
*
* @category traversing
* @since 2.11.0
*/
export var traverseReadonlyArrayWithIndex = function (f) {
var g = traverseReadonlyNonEmptyArrayWithIndex(f);
return function (as) { return (_.isNonEmpty(as) ? g(as) : ApT); };
};
/**
* Equivalent to `ReadonlyArray#traverseWithIndex(Applicative)`.
*
* @category traversing
* @since 2.9.0
*/
export var traverseArrayWithIndex = traverseReadonlyArrayWithIndex;
/**
* Equivalent to `ReadonlyArray#traverse(Applicative)`.
*
* @category traversing
* @since 2.9.0
*/
export var traverseArray = function (f) { return traverseReadonlyArrayWithIndex(function (_, a) { return f(a); }); };
/**
* Equivalent to `ReadonlyArray#sequence(Applicative)`.
*
* @category traversing
* @since 2.9.0
*/
export var sequenceArray =
/*#__PURE__*/ traverseArray(identity);
// -------------------------------------------------------------------------------------
// legacy
// -------------------------------------------------------------------------------------
/**
* Alias of `flatMap`.
*
* @category legacy
* @since 2.6.0
*/
export var chainW = flatMap;
/**
* Alias of `flatMap`.
*
* @category legacy
* @since 2.0.0
*/
export var chain = flatMap;
/**
* Alias of `tap`.
*
* @category legacy
* @since 2.0.0
*/
export var chainFirst = tap;
/**
* Alias of `tap`.
*
* @category legacy
* @since 2.11.0
*/
export var chainFirstW = tap;
// -------------------------------------------------------------------------------------
// deprecated
// -------------------------------------------------------------------------------------
/**
* This instance is deprecated, use small, specific instances instead.
* For example if a function needs a `Functor` instance, pass `R.Functor` instead of `R.reader`
* (where `R` is from `import R from 'fp-ts/Reader'`)
*
* @category zone of death
* @since 2.0.0
* @deprecated
*/
export var reader = {
URI: URI,
map: _map,
of: of,
ap: _ap,
chain: flatMap,
promap: _promap,
compose: _compose,
id: id,
first: first,
second: second,
left: left,
right: right
};
/**
* Use [`getApplySemigroup`](./Apply.ts.html#getapplysemigroup) instead.
*
* @category zone of death
* @since 2.0.0
* @deprecated
*/
export var getSemigroup = /*#__PURE__*/ getApplySemigroup(Apply);
/**
* Use [`getApplicativeMonoid`](./Applicative.ts.html#getapplicativemonoid) instead.
*
* @category zone of death
* @since 2.0.0
* @deprecated
*/
export var getMonoid = /*#__PURE__*/ getApplicativeMonoid(Applicative);
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