Ratios

Package: RATIO_PACKAGE. Registered by createEngine(); for a slimmer engine, register it explicitly (see choosing packages).

A ratio compares quantities: a 16:9 screen, a 2:1 mix, a 1:2:3 split. The same ratio can be written many ways (1920:1080 and 16:9 are the same shape), and ratio reduces one to its simplest whole-number form.

ratio(1920, 1080) // 16:9
ratio(4, 8) // 1:2
ratio(2, 4, 6) // 1:2:3

It takes any number of parts, so it works for a two-part aspect ratio or a several-part mix, and it divides them all by their largest common factor.

Why it is a function

ratio(16, 9) is written as a function rather than as 16:9, because a colon between two numbers is already taken: on its own 1:10 is a clock time (ten past one), and inside an aggregate it is a range, the run of numbers from 1 to 10 (see ranges). Keeping ratios as a function leaves those meanings of the colon untouched.

The parts must be whole positive numbers, and there must be at least two; anything else (a fraction, a negative, a single value) is reported as an error rather than guessed at.

A screen or an image

A pair written the way a screen is sold reduces the same way, without the brackets: 1920x1080 as ratio is 16:9. That spelling, and the resize that goes with it, are on screen and image sizes.