// wink-statistics
// Fast and Numerically Stable Statistical Analysis Utilities.
//
// Copyright (C) GRAYPE Systems Private Limited
//
// This file is part of “wink-statistics”.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
// ## streaming
var getValidFD = require( './get-valid-fd.js' );
// ### sum
/**
*
* Sum is computed incrementally with arrival of each value from the data stream.
*
* The [`compute()`](https://winkjs.org/wink-statistics/Stream.html#compute) requires
* a single numeric value as argument.
*
* The [`result()`](https://winkjs.org/wink-statistics/Stream.html#result) returns
* an object containing `sum`.
*
* @memberof streaming#
* @return {Stream} Object containing methods such as `compute()`, `result()` & `reset()`.
* @example
* var addition = sum();
* addition.compute( 1 );
* addition.compute( 10e+100 );
* addition.compute( 1 );
* addition.compute( -10e+100 );
* addition.value();
* // returns 2
* addition.result();
* // returns { sum: 2 }
*/
var sum = function () {
var items = false;
var total = 0;
var compensation = 0;
var methods = Object.create( null );
methods.compute = function ( di ) {
var t;
if ( items ) {
t = total + di;
compensation += ( Math.abs( total ) >= Math.abs( di ) ) ?
( ( total - t ) + di ) :
( ( di - t ) + total );
total = t;
} else {
total = di;
items = true;
}
return undefined;
}; // compute()
methods.value = function ( fractionDigits ) {
var fd = getValidFD( fractionDigits );
return +( total + compensation ).toFixed( fd );
}; // value()
methods.result = function ( fractionDigits ) {
var fd = getValidFD( fractionDigits );
return { sum: +( total + compensation ).toFixed( fd ) };
}; // result()
methods.reset = function () {
items = false;
total = 0;
compensation = 0;
}; // reset()
return methods;
}; // sum()
module.exports = sum;