Compiling Expressions

The Compute Engine LaTeX expressions can compile expressions to JavaScript functions!

Introduction

Some expressions can take a long time to evaluate numerically, for example if they contain a large number of terms or involve a loop \((\sum\) or \(\prod\)).

In this case, it is useful to compile the expression into a JavaScript function that can be evaluated much faster.

For example this approximation: \pi \approx \textstyle\sqrt{6\sum^{10^6}_{n=1}\frac{1}{n^2}}

const expr = ce.parse("\\sqrt{6\\sum^{10^2}_{n=1}\\frac{1}{n^2}}"); // Numerical evaluation using the Compute Engine console.time('evaluate'); console.timeEnd('evaluate', expr.evaluate()); // Compilation to a JavaScript function and execution console.time('compile'); const fn = expr.compile(); console.timeEnd('compile', fn());

Compiling

To get a compiled version of an expression use the expr.compile() method:

const expr = ce.parse("2\\prod_{n=1}^{\\infty} \\frac{4n^2}{4n^2-1}");
const fn = expr.compile();

To evaluate the compiled expression call the function returned by expr.compile():

console.log(fn());
// ➔ 3.141592653589793

If the expression cannot be compiled, the compile() method will throw an error.

Arguments

The function returned by expr.compile() can be called with an object literal containing the value of the arguments:

const expr = ce.parse("n^2"); const fn = expr.compile(); for (let i = 1; i < 10; i++) console.log(fn({ n: i }));

To get a list of the unknows of an expression use the expr.unknowns property:

console.log(ce.parse("n^2").unknowns); console.log(ce.parse("a^2+b^3").unknowns);

Limitations

The calculations are only performed using machine precision numbers.

Complex numbers, arbitrary precision numbers, and symbolic calculations are not supported.

Some functions are not supported.

If the expression cannot be compiled, the compile() method will throw an error. The expression can be numerically evaluated as a fallback:

function compileOrEvaluate(expr) { try { const fn = expr.compile(); return fn() + " (compiled)"; } catch (e) { return expr.N().numericValue + " (evaluated)"; } } // `expr.compile()` can handle this expression console.log(compileOrEvaluate(ce.parse("\\frac{\\sqrt{5}+1}{2}"))); // `expr.compile()` cannot handle complex numbers, so it throws // and we fall back to numerical evaluation with expr.N() console.log(compileOrEvaluate(ce.parse("-i\\sqrt{-1}")));