time-to-botec

main.js (5784B)

---

 /**
 * @license Apache-2.0
 *
 * Copyright (c) 2018 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.
 */
 
 'use strict';
 
 // MODULES //
 
 var join = require( 'path' ).join;
 var readFile = require( '@stdlib/fs/read-file' ).sync;
 var replace = require( '@stdlib/string/replace' );
 var isInteger = require( '@stdlib/assert/is-integer' ).isPrimitive;
 
 
 // VARIABLES //
 
 var opts = {
 	'encoding': 'utf8'
 };
 var dir = join( __dirname, 'templates' );
 
 // Templates:
 var COEFFICIENT_RATIO_TEMPLATE = readFile( join( dir, 'coefficient_ratio.js.txt' ), opts ); // eslint-disable-line id-length
 var EVALRATIONAL_TEMPLATE = readFile( join( dir, 'evalrational.js.txt' ), opts );
 var LOOP_TEMPLATE = readFile( join( dir, 'loop.js.txt' ), opts );
 var NAN_TEMPLATE = readFile( join( dir, 'nan.js.txt' ), opts );
 var MAX_CHARS = 66; // max-len (80) - chars already in line ('2x tab': 8, 's1 = ': 5, ';': 1)
 
 
 // FUNCTIONS //
 
 /**
 * Serializes a single value to a string.
 *
 * @private
 * @param {number} x - value to serialize
 * @returns {string} serialized value
 */
 function value2string( x ) {
 	var str = x.toString();
 	if ( isInteger( x ) ) {
 		str += '.0';
 	}
 	return str;
 }
 
 /**
 * Serializes an array of numbers to an indented newline separated list.
 *
 * @private
 * @param {NumericArray} x - array of numbers
 * @returns {string} serialized value
 */
 function array2list( x ) {
 	var str;
 	var n;
 	var m;
 	var i;
 
 	n = x.length;
 	m = n - 1;
 	str = '';
 	for ( i = 0; i < n; i++ ) {
 		str += '\t' + x[ i ].toString();
 		if ( isInteger( x[ i ] ) ) {
 			str += '.0';
 		}
 		if ( i < m ) {
 			str += ',\n';
 		}
 	}
 	return str;
 }
 
 /**
 * Serializes an array of coefficients to a string implementing Horner's method.
 *
 * @private
 * @param {NumericArray} x - coefficients sorted in ascending degree
 * @returns {string} output string
 */
 function hornerAscending( x ) {
 	var str;
 	var n;
 	var m;
 	var i;
 
 	n = x.length;
 	m = n - 1;
 	str = x[ 0 ].toString();
 	if ( isInteger( x[ 0 ] ) ) {
 		str += '.0';
 	}
 	for ( i = 1; i < n; i++ ) {
 		str += ' + (x * ';
 		if ( i < m ) {
 			str += '(';
 		}
 		str += x[ i ].toString();
 		if ( isInteger( x[ i ] ) ) {
 			str += '.0';
 		}
 	}
 	// Close all the parentheses...
 	for ( i = 0; i < (2*m)-1; i++ ) {
 		str += ')';
 	}
 	return str;
 }
 
 /**
 * Serializes an array of coefficients to a string implementing Horner's method.
 *
 * @private
 * @param {NumericArray} x - coefficients sorted in descending degree
 * @returns {string} output string
 */
 function hornerDescending( x ) {
 	var str;
 	var m;
 	var i;
 
 	m = x.length - 1;
 	str = x[ m ].toString();
 	if ( isInteger( x[ m ] ) ) {
 		str += '.0';
 	}
 	for ( i = m-1; i >= 0; i-- ) {
 		str += ' + (x * ';
 		if ( i > 0 ) {
 			str += '(';
 		}
 		str += x[ i ].toString();
 		if ( isInteger( x[ i ] ) ) {
 			str += '.0';
 		}
 	}
 	// Close all the parentheses...
 	for ( i = 0; i < (2*m)-1; i++ ) {
 		str += ')';
 	}
 	return str;
 }
 
 /**
 * Replaces the specified tag in a source string by the chosen replacement and adds directive to disable the maximum line length lint rule if necessary.
 *
 * @private
 * @param {string} src - source string
 * @param {string} target - target tag
 * @param {string} str - replacement
 * @returns {string} output string
 */
 function replaceString( src, target, str ) {
 	var out = replace( src, '{{'+target+'}}', str );
 	if ( str.length > MAX_CHARS ) {
 		out = replace( out, '{{'+target+'_ESLINT}}', ' // eslint-disable-line max-len' );
 	} else {
 		out = replace( out, '{{'+target+'_ESLINT}}', '' );
 	}
 	return out;
 }
 
 
 // MAIN //
 
 /**
 * Compiles a module string which exports a function for evaluating a rational function.
 *
 * @param {NumericArray} P - numerator polynomial coefficients sorted in ascending degree
 * @param {NumericArray} Q - denominator polynomial coefficients sorted in ascending degree
 * @returns {string} module string exporting a function for evaluating a rational function
 *
 * @example
 * var P = [ -6.0, -5.0 ];
 * var Q = [ 3.0, 0.5 ];
 *
 * var str = compile( P, Q );
 * // returns <string>
 */
 function compile( P, Q ) {
 	var str;
 	var n;
 
 	n = P.length;
 
 	// If no coefficients, the function always returns NaN...
 	if ( n === 0 ) {
 		return NAN_TEMPLATE;
 	}
 	// If P and Q have different lengths, the function always returns NaN...
 	if ( n !== Q.length ) {
 		return NAN_TEMPLATE;
 	}
 	// If P and Q only have one coefficient, the function always returns the ratio of those coefficients...
 	if ( n === 1 ) {
 		return replace( COEFFICIENT_RATIO_TEMPLATE, '{{ratio}}', value2string( P[0] / Q[0] ) );
 	}
 	// Avoid exceeding the maximum stack size on V8 by using a simple loop :(. Note that the choice of `500` was empirically determined...
 	if ( n > 500 ) {
 		str = replace( LOOP_TEMPLATE, '{{P}}', array2list( P ) );
 		str = replace( str, '{{Q}}', array2list( Q ) );
 		return replace( str, '{{ratio}}', value2string( P[0]/Q[0] ) );
 	}
 	// If more than one coefficient, apply Horner's method...
 	str = replaceString( EVALRATIONAL_TEMPLATE, 'P_ASCENDING', hornerAscending( P ) );
 	str = replaceString( str, 'Q_ASCENDING', hornerAscending( Q ) );
 	str = replaceString( str, 'P_DESCENDING', hornerDescending( P ) );
 	str = replaceString( str, 'Q_DESCENDING', hornerDescending( Q ) );
 	return replace( str, '{{ratio}}', value2string( P[0]/Q[0] ) );
 }
 
 
 // EXPORTS //
 
 module.exports = compile;