TypeScript Math

Math is already there

Arithmetic operators handle plus, minus, times, and divide. Square roots, powers, and rounding live on theMath object. You do not include a header. C++ needed <cmath>. TypeScript does not.

The functions take and return number. Store the result in a number unless you have a reason not to.

A complete program

This file uses the four functions you will see most often: Math.sqrt, Math.pow,Math.abs, and Math.round. Copy it, change the numbers, and compile again.

const side: number = 9;
console.log("sqrt(9) = " + Math.sqrt(side));
console.log("pow(2, 8) = " + Math.pow(2, 8));
console.log("abs(-4.5) = " + Math.abs(-4.5));
console.log("round(2.6) = " + Math.round(2.6));

Math.sqrt

Math.sqrt(x) returns the square root of x. Pass a non-negative number. A negative argument yields NaN (not a number) instead of a useful result.

Distance formulas use square roots. The length of a right-triangle hypotenuse with legs 3 and 4 isMath.sqrt(3 * 3 + 4 * 4), which is 5.

const a: number = 3;
const b: number = 4;
const c: number = Math.sqrt(a * a + b * b);
console.log(c);

Math.pow

Math.pow(base, exp) raises base to exp. Both arguments arenumber, so the result is a number even when the inputs look like integers.

For a small integer power you can still write n * n, or 2 ** 8. UseMath.pow when you want the call to be obvious, or when the exponent is already in a variable.

Math.abs and Math.round

Math.abs(x) returns the absolute value: negative numbers become positive, positive numbers stay positive. Use it when a difference might go either way and you only care about size.

Math.round(x) returns the nearest integer as a number. Halfway cases (such as 2.5) round toward plus infinity, so 2.5 becomes 3 and -2.5 becomes -2. That halfway rule differs from C++round, which rounds away from zero.

console.log(Math.abs(-12));
console.log(Math.abs(7.25));
console.log(Math.round(3.2));
console.log(Math.round(3.8));
console.log(Math.round(2.5));
console.log(Math.round(-2.5));

The usual toolkit

Math.floor and Math.ceil live on the same object. You do not need them yet; know they exist so you do not reinvent them.

Types and mistakes

• These functions return number. There is no separate integer type to truncate into.
• Do not take Math.sqrt of a negative number if you expect a real result.
• Math.pow is slower than a simple multiply. For squares, write x * x.

Next: boolean values, which math comparisons produce.