Instructions

A dot matrix is a two dimensional image made up of dots and whitespace. The dots form the intended image on the background of the whitespace.

A dot matrix image can be stored and manipulated in memory as a two dimensional Matrix. In what follows, the "whitespace" in the matrices will be signified as 0 and the "dots" will be non-zero.

1. Define the Exercism logo Matrix

The Matrix looks as follows, with 0 as a whitespace and 1 as a dot:

If you "render" it, it looks like this:

2. Define functions that make the logo frown

Define frown!() and frown() functions that take the Exercism logo Matrix. Return a Matrix with the smiling mouth changed to a frowning mouth.

The resulting Matrix would render like this:

3. Put together a stickerwall

Define the function stickerwall(), which takes the Exercism matrix as input. Return a Matrix of the dot matrix which renders as:

4. Change dots to column pixel counts

We aren't limited to just using 1 as the dot, so we could encode other useful information if desired. Define the function colpixelcount() which takes any dot matrix with 1 dots as input. Return a dot matrix of the same size, with the dots in each column being the number of dots in that column.

With the Exercism logo Matrix as input, the output is a Matrix as follows:

5. Render a dot matrix

Rather than just talk about rendering our creations, we would like to actually be able to do that for easy viewing. Define the function render() which takes a dot matrix as input. Return a string with dots rendered as 'X', the 0s as ' ', and newlines connecting each row.

When printed, this should render the Exercism Matrix as expected.

This should also work with "dots" that are different than 1: