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modify concept exercise exercism-matrix (#997)
* modify concept exercise exercism-matrix * adjust hints.md
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‎config.json

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],
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"status": "wip"
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},
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{
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"slug": "exercism-matrix",
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"name": "Exercism Matrix",
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"uuid": "36cbda04-3921-4491-9ec6-76951f00aa00",
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"concepts": [
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"multi-dimensional-arrays"
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],
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"prerequisites": [
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"function-composition"
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],
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"status": "wip"
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},
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{
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"slug": "old-elyses-enchantments",
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"name": "Old Elyse's Enchantments",
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"prerequisites": [],
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"status": "deprecated"
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},
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{
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"slug": "old-exercism-matrix",
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"name": "Old The Exercism Matrix",
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"uuid": "36cbda04-3921-4491-9ec6-76951f00aa00",
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"concepts": [],
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"prerequisites": [],
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"status": "deprecated"
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},
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{
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"slug": "old-emoji-times",
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"name": "Old 🕑🕤🕗",

‎exercises/concept/exercism-matrix/.docs/hints.md

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# Hints
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The introduction contains most of what is needed for this exercise.
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## 1. Define the Exercism logo `Matrix`
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- Get creative! However, you can also simply copy and paste from the instructions.
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## 2. Define functions that make the logo frown
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- Remember that functions ending in `!` mutate the input (modify in-place), while others do not.
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- `frown!` can be done via assignment of specific elements, or (less efficiently) by swapping two rows.
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- `frown` is going to be very similar to `frown!`, just returning a copy of the input matrix.
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## 3. Put together a stickerwall
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- Use your `frown()` function.
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- The `vcat()` and `hcat()` functions, or their equivalents, are your friends here.
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- The `ones()` and `zeros()` functions can also be quite useful.
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## 4. Change dots to column pixel counts
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- Broadcasting is a great way to do this concisely.
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- To broadcast, you'll need a vector with the column dot counts.
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- To get a vector with column dot count, you can apply a function to the `Matrix`.
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## 5. Render a dot matrix
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- Using `eachrow()` to loop may work well here.
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- The function `join()` can also help.

‎exercises/concept/exercism-matrix/.docs/instructions.md

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# Instructions
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A dot matrix is a two dimensional image made up of *dots* and *whitespace*.
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The dots form the intended image on the background of the whitespace.
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A dot matrix image can be stored and manipulated in memory as a two dimensional `Matrix`.
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In what follows, the "whitespace" in the matrices will be signified as `0` and the "dots" will be non-zero.
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## 1. Define the Exercism logo `Matrix`
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The `Matrix` looks as follows, with `0` as a whitespace and `1` as a dot:
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```julia
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[
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0 0 1 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0;
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0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0;
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0 1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 1 0;
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0 1 0 0 1 0 1 0 0 0 0 1 0 1 0 0 1 0;
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0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0;
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1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1;
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0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0;
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0 1 0 0 0 0 0 1 0 0 1 0 0 0 0 0 1 0;
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0 1 0 0 0 0 0 0 1 1 0 0 0 0 0 0 1 0;
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0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0;
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0 0 1 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0;
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]
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```
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If you "render" it, it looks like this:
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```julia
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XX XX
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X X
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X X X X
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X X X X X X
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X X
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X X
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X X X X
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X X X X
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X XX X
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X X
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XX XX
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```
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## 2. Define functions that make the logo frown
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Define `frown!()` and `frown()` functions that take the Exercism logo `Matrix`.
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Return a `Matrix` with the smiling mouth changed to a frowning mouth.
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The resulting `Matrix` would render like this:
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```julia
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XX XX
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X X
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X X X X
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X X X X X X
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X X
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X X
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X XX X
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X X X X
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X X X X
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X X
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XX XX
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```
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## 3. Put together a stickerwall
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Define the function `stickerwall()`, which takes the Exercism matrix as input.
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Return a `Matrix` of the dot matrix which renders as:
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```julia
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XX XX X XX XX
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X X X X X
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X X X X X X X X X
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X X X X X X X X X X X X X
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X X X X X
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X X X X X
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X X X X X X XX X
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X X X X X X X X X
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X XX X X X X X X
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X X X X X
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XX XX X XX XX
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X
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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X
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XX XX X XX XX
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X X X X X
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X X X X X X X X X
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X X X X X X X X X X X X X
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X X X X X
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X X X X X
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X XX X X X X X X
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X X X X X X X X X
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X X X X X X XX X
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X X X X X
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XX XX X XX XX
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```
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## 4. Change dots to column pixel counts
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We aren't limited to just using `1` as the dot, so we could encode other useful information if desired.
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Define the function `colpixelcount()` which takes *any* dot matrix with `1` dots as input.
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Return a dot matrix of the same size, with the dots in each column being the number of dots in that column.
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With the Exercism logo `Matrix` as input, the output is a `Matrix` as follows:
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```julia
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[
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0 0 2 2 0 0 0 0 0 0 0 0 0 0 2 2 0 0;
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0 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0;
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0 8 0 0 0 1 0 0 0 0 0 0 1 0 0 0 8 0;
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0 8 0 0 1 0 2 0 0 0 0 2 0 1 0 0 8 0;
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0 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0;
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1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1;
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0 8 0 0 0 0 2 0 0 0 0 2 0 0 0 0 8 0;
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0 8 0 0 0 0 0 1 0 0 1 0 0 0 0 0 8 0;
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0 8 0 0 0 0 0 0 1 1 0 0 0 0 0 0 8 0;
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0 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0;
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0 0 2 2 0 0 0 0 0 0 0 0 0 0 2 2 0 0;
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]
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```
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## 5. Render a dot matrix
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Rather than just talk about rendering our creations, we would like to actually be able to do that for easy viewing.
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Define the function `render()` which takes a dot matrix as input.
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Return a string with dots rendered as `'X'`, the `0`s as `' '`, and newlines connecting each row.
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```julia-repl
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julia> render(E)
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" XX XX \n X X \n X X X X \n X X X X X X \n X X \nX X\n X X X X \n X X X X \n X XX X \n X X \n XX XX "
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```
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When printed, this should render the Exercism Matrix as expected.
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```julia-repl
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julia> print(render(E))
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XX XX
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X X
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X X X X
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X X X X X X
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X X
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X X
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X X X X
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X X X X
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X XX X
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X X
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XX XX
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```
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This should also work with "dots" that are different than `1`:
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```julia-repl
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julia> print(render(colpixelcount(E)))
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XX XX
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X X
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X X X X
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X X X X X X
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X X
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X X
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X X X X
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X X X X
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X XX X
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X X
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XX XX
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```

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