Awesome

math-expression-evaluator

An extremely efficient, flexible and amazing evaluator for Math expression in Javascript.

Use cases

Input	Result	Explanation
2+3-1	4	Addition and Subtraction operator
*25/10**	1	Multiplication and Division operator
tan45 or tan(45)	1	Trigonometric Function (tan in Degree mode)
tan45 or tan(45)	1.619775190543862	Trigonometric Function (tan in Radian mode)
Pi1,15,n or Pi(1,15,n)	1307674368000	Product of Sequence
Sigma1,15,n or Sigma(1,15,n)	120	Sum of Sequence (also called summation)
2^3	8	Exponent (note this operator is left associative like MS Office)
5P3	60	Permutaion Method to calculate all the permutaions
sincostan90 or sin(cos(tan(90)))	0.017261434031253	Multiple functions with or without parenthesis (both works)

Fiddle Yourself

Installation

Node JS

Using npm

npm install math-expression-evaluator

Browser

Using bower

bower install math-expression-evaluator

Usage

Using eval method of mexp object

const mexp = new Mexp() var value = mexp.eval(exp); // 2 + 2

Using constituents of eval methods of mexp object

Create mexp object
```
 const mexp = new Mexp
```
Parse an expression and then add additional detail to the tokens using
```
 var lexed = mexp.lex("expression");
```
which returns an array of token which will be further processed by methods toPostfix and postfixEval
Now, that array is needed to be converted to postfix notation using
```
 var postfixed = mexp.toPostfix(lexed);  
```
which converts the array to postfix notation and return new array
Now to get the value of expression use postfixEval
```
 var result = mexp.postfixEval(postfixed);  
```
where result contains the result.

Extending tokens

Defining a token

A token is defined similar way as 1.x version. You may refer to test file on examples on how to add tokens. Since this package is TS compatible, you will get autocomplete on mexp.addToken

Adding tokens using addToken method of mexp object

 const mexp = new Mexp()
 mexp.addToken([token1, token2]) // tokens once added will be preserved in later evaluations

Adding tokens using eval method of mexp object

 const mexp = new Mexp()
 mexp.eval("expression", [token1, token2]) // tokens once added will be preserved in later evaluations

Adding token using constituents of eval method of mexp object

 const mexp = new Mexp()
 const answer = mexp.postfixEval(mexp.toPostfix(mexp.lexed("expression", [token1, token2]))) // tokens once added will be preserved in later evaluations
 console.log(answer)

How to run test

npm test

Supported symbols

Symbol	Explanation
+	Addition Operator eg. 2+3 results 5
-	Subtraction Operator eg. 2-3 results -1
/	Division operator eg 3/2 results 1.5
*	Multiplication Operator eg. 2*3 results 6
Mod	Modulus Operator eg. 3 Mod 2 results 1
(	Opening Parenthesis
)	Closing Parenthesis
&	Bitwise AND eg. 3&1 results 1
Sigma	Summation eg. Sigma(1,100,n) results 5050
Pi	Product eg. Pi(1,10,n) results 3628800
n	Variable for Summation or Product
pi	Math constant pi returns 3.14
e	Math constant e returns 2.71
C	Combination operator eg. 4C2 returns 6
P	Permutation operator eg. 4P2 returns 12
!	factorial operator eg. 4! returns 24
log	logarithmic function with base 10 eg. log 1000 returns 3
ln	natural log function with base e eg. ln 2 returns .3010
pow	power function with two operator pow(2,3) returns 8
^	power operator eg. 2^3 returns 8
root	underroot function root 4 returns 2
sin	Sine function
cos	Cosine function
tan	Tangent function
asin	Inverse Sine function
acos	Inverse Cosine function
atan	Inverse Tangent function
sinh	Hyperbolic Sine function
cosh	Hyperbolic Cosine function
tanh	Hyperbolic Tangent function
asinh	Inverse Hyperbolic Sine function
acosh	Inverse Hyperbolic Cosine function
atanh	Inverse Hyperbolic Tangent function

Features

Amazing support for Sigma and Pi

This is a fantastic feature of this calculator that it is capable of evaluating expressions containing Sigma and Pi. Passing Sigma(1,100,n) will evaluate to 5050 as n is summationed from 1 to 100. and Pi(1,15,n) will evaluate to 1307674368000 as n is multiplied from 1 to 15 which is equal to 15!

Parenthesis less expression

If a expression is readable by human then it is readable by this evaluator. There is no need to wrap every function inside parenthesis. For eg. sin90 will work totally fine instead of sin(90)

##Changelog

Removed lodash.indexof and used native Array.prototype.indexOf hence dropping suppports for IE8 and below.

This will reflect in next release named v1.2.16