@stdlib/math
Version:
Standard math.
229 lines (212 loc) • 6.01 kB
JavaScript
/**
* @license Apache-2.0
*
* Copyright (c) 2020 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
;
// MODULES //
var setReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
var isFunction = require( '@stdlib/assert/is-function' );
var isIteratorLike = require( '@stdlib/assert/is-iterator-like' );
var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
var iteratorSymbol = require( '@stdlib/symbol/iterator' );
var format = require( '@stdlib/string/format' );
var validate = require( './validate.js' );
// MAIN //
/**
* Returns an iterator which invokes a binary function accepting numeric arguments for each iterated value.
*
* ## Notes
*
* - When invoked, the input function is provided two arguments:
*
* - `x`: iterated value from first input iterator
* - `y`: iterated value from second input iterator
*
* - If provided a numeric value as an iterator argument, the value is broadcast as an **infinite** iterator which **always** returns the provided value.
*
* - If an iterated value is non-numeric (including `NaN`), the returned iterator returns `NaN`. If non-numeric iterated values are possible, you are advised to provide an iterator which type checks and handles non-numeric values accordingly.
*
* - The length of the returned iterator is equal to the length of the shortest provided iterator. In other words, the returned iterator ends once **one** of the provided iterators ends.
*
* - If an environment supports `Symbol.iterator` and all provided iterators are iterable, the returned iterator is iterable.
*
* @param {Iterator} iter0 - first input iterator
* @param {Iterator} iter1 - second input iterator
* @param {Function} fcn - function to invoke
* @param {Options} [options] - options
* @param {*} [options.invalid=NaN] - return value when an input iterator yields a non-numeric value
* @throws {TypeError} first argument must be an iterator protocol-compliant object
* @throws {TypeError} second argument must be an iterator protocol-compliant object
* @throws {TypeError} third argument must be a function
* @throws {TypeError} options argument must be an object
* @throws {TypeError} must provide valid options
* @returns {Iterator} iterator
*
* @example
* var randu = require( '@stdlib/random/iter/randu' );
* var copysign = require( '@stdlib/math/base/special/copysign' );
*
* var iter = iterMap2( randu(), randu(), copysign );
*
* var r = iter.next().value;
* // returns <number>
*
* r = iter.next().value;
* // returns <number>
*
* r = iter.next().value;
* // returns <number>
*
* // ...
*/
function iterMap2( iter0, iter1, fcn, options ) {
var iterators;
var values;
var types;
var niter;
var iter;
var opts;
var FLG;
var err;
var i;
niter = 2;
values = [ 0.0, 0.0 ];
iterators = [];
types = [];
for ( i = 0; i < niter; i++ ) {
iterators.push( arguments[ i ] );
if ( isIteratorLike( arguments[ i ] ) ) {
types.push( 1 );
} else if ( isNumber( arguments[ i ] ) ) {
types.push( 0 );
} else {
throw new TypeError( format( 'invalid argument. Must provide an iterator protocol-compliant object or a number. Argument: `%u`. Value: `%s`.', i, arguments[ i ] ) );
}
}
if ( !isFunction( fcn ) ) {
throw new TypeError( format( 'invalid argument. Third argument must be a function. Value: `%s`.', fcn ) );
}
opts = {
'invalid': NaN
};
if ( arguments.length > 3 ) {
err = validate( opts, options );
if ( err ) {
throw err;
}
}
// Create an iterator protocol-compliant object:
iter = {};
setReadOnly( iter, 'next', next );
setReadOnly( iter, 'return', end );
// If an environment supports `Symbol.iterator` and all provided iterators are iterable, make the iterator iterable:
if ( iteratorSymbol ) {
for ( i = 0; i < niter; i++ ) {
if ( types[ i ] && !isFunction( iterators[ i ][ iteratorSymbol ] ) ) { // eslint-disable-line max-len
FLG = true;
break;
}
}
if ( !FLG ) {
setReadOnly( iter, iteratorSymbol, factory );
}
}
FLG = false;
return iter;
/**
* Returns an iterator protocol-compliant object containing the next iterated value.
*
* @private
* @returns {Object} iterator protocol-compliant object
*/
function next() {
var err;
var v;
var i;
if ( FLG ) {
return {
'done': true
};
}
for ( i = 0; i < niter; i++ ) {
if ( types[ i ] ) {
v = iterators[ i ].next();
if ( v.done ) {
FLG = true;
return v;
}
if ( typeof v.value === 'number' ) {
values[ i ] = v.value;
} else {
err = true;
}
} else {
values[ i ] = iterators[ i ];
}
}
if ( err ) {
return {
'value': opts.invalid,
'done': false
};
}
return {
'value': fcn( values[ 0 ], values[ 1 ] ),
'done': false
};
}
/**
* Finishes an iterator.
*
* @private
* @param {*} [value] - value to return
* @returns {Object} iterator protocol-compliant object
*/
function end( value ) {
FLG = true;
if ( arguments.length ) {
return {
'value': value,
'done': true
};
}
return {
'done': true
};
}
/**
* Returns a new iterator.
*
* @private
* @returns {Iterator} iterator
*/
function factory() {
var args;
var i;
args = [];
for ( i = 0; i < niter; i++ ) {
if ( types[ i ] ) {
args.push( iterators[ i ][ iteratorSymbol ]() );
} else {
args.push( iterators[ i ] );
}
}
args.push( fcn, opts );
return iterMap2.apply( null, args );
}
}
// EXPORTS //
module.exports = iterMap2;