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Nemathode is array based mathematical expression notation (further in the text: nematode/s, expression/s).

[0, '+', 1] === (0 + 1)

[0, '+', 1, '*', [2, '/', 3, '-', 4]] === (0 + 1б * (2 / 3 - 4))

Nemathode.js is a JavaScript library for nemathodes evaluation. It lets you to combine any number of libraries while leaving the format of the expressions unchanged (aggregator of solutions under one format)

const res1 = nemathode.evaluate([0, '+', 1]); // 1
const res2 = nemathode.evaluate([0, '+', 1, '*', [2, '/', 1, '-', 3]]); // -1

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Installation

$ npm install --save nemathode

or

$ yarn add nemathode

Fast introduction

Read article here

Examples

• binary operators

const sumOperator = nemathode.evaluate([1, '+', 1]); // 2
const mulOperator = nemathode.evaluate([1, '*', 1]); // 1

• functions

const customFunction = nemathode.evaluate([1, '+', ['abs', 1, 2, 3]]); //a rguments are not evaluated (future)
const singleFunction = nemathode.evaluate([['abs', 1, 2, 3]]; // single function syntax (it's not convinient, but for now it's only way)
const boolResult = nemathode.evaluate([['areEqual', 1, 2, 3]]); // returns boolean
// etc

• math constants

const piConst = nemathode.mathConstants.PI;
const piConstInUse = nemathode.evaluate([1, '+', 'PI']);

• nested expressions

const resOfNestedExp = nemathode.evaluate([1, '+', 'PI', '*', ['abs', 1, 2, 3], '-', [1, '+', [1, '/', 25]]]);

Configuration

mathConstants

Literally, mathematical constants

• full example

functions

Set of records with implementations

• full example

toInputType

It seems excessive but not everyone using pure js functionality. There are set of libraries where intermediate type is not a number, for example: bignumber.js, decimal.js etc (we have on our website set of configs for most popular libs). So you can configure entry handler for them like

const toInputType = (val: unknown): Decimal | unknown => {
	if (typeof val === 'number') {
		const input = new Decimal(val);

		return input;
	}

	return val;
};

toOutputType

Opposite of toInputType. See at an example

const toOutputValue = (val: unknown): number | boolean => {
	if (val instanceof Decimal) {
		return val.toNumber();
	}

	return val;
};

binaryOperators

Let's look at one of examples

...
    '+': {
        precedence: 1,
        implementation: (l: number, r: number): number => {
            return l + r;
        },
    }
...

It's a configuration for operator that consists from two (by now) fields: precedence, implementation (the same as in functions).

example (pure js)

const config = {
		mathConstants: {
			'E': Math.E,
			'LN2': Math.LN2,
			'LN10': Math.LN10,
			'LOG10E': Math.LOG10E,
			'LOG2E': Math.LOG2E,
			'PI': Math.PI,
			'SQRT1_2': Math.SQRT1_2,
			'SQRT2': Math.SQRT2,
		},
		functions: {
			'abs': {
				implementation: Math.abs,
			},
			'min': {
				implementation: Math.min,
			},
			'areEqual': {
				implementation: (...args: number[]): boolean => {
					return args.every(v => v === args[0]);
				},
			},
		},
		toInputType: (val: unknown): unknown => val,
		toOutputValue: (val: unknown): number | boolean => val as number | boolean,
		binaryOperators: {
			'+': {
				precedence: 1,
				implementation: (l: number, r: number): number => {
					return l + r;
				},
			},
			'-': {
				precedence: 1,
				implementation: (l: number, r: number): number => {
					return l - r;
				},
			},
			'*': {
				precedence: 2,
				implementation: (l: number, r: number): number => {
					return l * r;
				},
			},
			'/': {
				precedence: 2,
				implementation: (l: number, r: number): number => {
					return l / r;
				},
			},
			'%': {
				precedence: 2,
				implementation: (l: number, r: number): number => {
					return l % r;
				},
			},
		},
	};

API

import Nemathode from 'nemathode';
import { config } from './config';

const nemathode = Nemathode({
    ...config,
});

// method for expression evaluation
const res = nemathode.evaluate([...]);

// example of getting math constant
nemathode.mathConstants.SOME_CONST;

License

MIT © Kas Elvirov