KAS

A lightweight JavaScript CAS (Computer Algebra System) for comparing expressions and equations. It is used throughout Khan Academy's interactive exercises.

What can it do?

It can parse plain text math, LaTeX, or a mix of both:

var expr = KAS.parse("3x \\frac{42}{42} sin^2y").expr;
expr.print();
// "3*x*42/42*sin(y)^(2)"

It can evaluate expressions:

var expr = KAS.parse("(x^2+y^2)^.5").expr;
expr.eval({x: 3, y: 4});
// 5

It can compare expressions and equations:

var expr1 = KAS.parse("(1-x)(-1-6x)").expr;
var expr2 = KAS.parse("(6x+1)(x-1)").expr;
KAS.compare(expr1, expr2).equal;
// true

var eq1 = KAS.parse("2w+50/w=25").expr;
var eq2 = KAS.parse("w(12.5-w)=25").expr;
KAS.compare(eq1, eq2).equal;
// true

It can perform basic transforms that always simplify an expression:

var expr = KAS.parse("1+1+x+x+x+y").expr;
expr.collect().print();
// "2+3*x+y"

var expr = KAS.parse("b^(2*y*log_b x)").expr;
expr.collect().print();
// "x^(2*y)"

It can perform non-simplifying transforms on an expression:

var expr = KAS.parse("ab(c+d)e^f").expr;
expr.print();
// "a*b*(c+d)*e^(f)"
expr.expand().print();
// "a*b*e^(f)*c+a*b*e^(f)*d"
expr.expand().factor().print();
// "a*b*e^(f)*(c+d)"

It can combine the above abilities to perform powerful simplification:

var expr = KAS.parse("((nx^5)^5)/(n^-2x^2)^-3").expr;
expr.print();
// "(n*x^(5))^(5)*(n^(-2)*x^(2))^(-1*-3)"
expr.simplify().print();
// "n^(-1)*x^(31)"

var expr = KAS.parse("(15np-25mp)/(15p^2-5p)+(20mp+10p^2)/(15p^2-5p)").expr;
expr.print();
// "(15*n*p+-25*m*p)*(15*p^(2)+-5*p)^(-1)+(20*m*p+10*p^(2))*(15*p^(2)+-5*p)^(-1)"
expr.simplify().print();
// "(-1+3*p)^(-1)*(3*n+-1*m+2*p)"

How to build the library

npm install
npm run build

How to build the parser

First, make any changes in src/parser-generator.js

npm install
npm run build:parser

License

MIT License