/** * @license Apache-2.0 * * Copyright (c) 2022 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 isNumber = require( './is_number.js' ); // NOTE: for the following, we explicitly avoid using stdlib packages in this particular package in order to avoid circular dependencies. var abs = Math.abs; // eslint-disable-line stdlib/no-builtin-math var lowercase = String.prototype.toLowerCase; var uppercase = String.prototype.toUpperCase; var replace = String.prototype.replace; // VARIABLES // var RE_EXP_POS_DIGITS = /e\+(\d)$/; var RE_EXP_NEG_DIGITS = /e-(\d)$/; var RE_ONLY_DIGITS = /^(\d+)$/; var RE_DIGITS_BEFORE_EXP = /^(\d+)e/; var RE_TRAILING_PERIOD_ZERO = /\.0$/; var RE_PERIOD_ZERO_EXP = /\.0*e/; var RE_ZERO_BEFORE_EXP = /(\..*[^0])0*e/; // MAIN // /** * Formats a token object argument as a floating-point number. * * @private * @param {Object} token - token object * @throws {Error} must provide a valid floating-point number * @returns {string} formatted token argument */ function formatDouble( token ) { var digits; var out; var f = parseFloat( token.arg ); if ( !isFinite( f ) ) { // NOTE: We use the global `isFinite` function here instead of `@stdlib/math/base/assert/is-finite` in order to avoid circular dependencies. if ( !isNumber( token.arg ) ) { throw new Error( 'invalid floating-point number. Value: ' + out ); } // Case: NaN, Infinity, or -Infinity f = token.arg; } switch ( token.specifier ) { case 'e': case 'E': out = f.toExponential( token.precision ); break; case 'f': case 'F': out = f.toFixed( token.precision ); break; case 'g': case 'G': if ( abs( f ) < 0.0001 ) { digits = token.precision; if ( digits > 0 ) { digits -= 1; } out = f.toExponential( digits ); } else { out = f.toPrecision( token.precision ); } if ( !token.alternate ) { out = replace.call( out, RE_ZERO_BEFORE_EXP, '$1e' ); out = replace.call( out, RE_PERIOD_ZERO_EXP, 'e'); out = replace.call( out, RE_TRAILING_PERIOD_ZERO, '' ); } break; default: throw new Error( 'invalid double notation. Value: ' + token.specifier ); } out = replace.call( out, RE_EXP_POS_DIGITS, 'e+0$1' ); out = replace.call( out, RE_EXP_NEG_DIGITS, 'e-0$1' ); if ( token.alternate ) { out = replace.call( out, RE_ONLY_DIGITS, '$1.' ); out = replace.call( out, RE_DIGITS_BEFORE_EXP, '$1.e' ); } if ( f >= 0 && token.sign ) { out = token.sign + out; } out = ( token.specifier === uppercase.call( token.specifier ) ) ? uppercase.call( out ) : lowercase.call( out ); return out; } // EXPORTS // module.exports = formatDouble;