84 lines
3.5 KiB
Markdown
84 lines
3.5 KiB
Markdown
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@def title = "Code blocks"
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@def hascode = true
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@def date = Date(2019, 3, 22)
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@def rss = "A short description of the page which would serve as **blurb** in a `RSS` feed; you can use basic markdown here but the whole description string must be a single line (not a multiline string). Like this one for instance. Keep in mind that styling is minimal in RSS so for instance don't expect maths or fancy styling to work; images should be ok though: "
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@def tags = ["syntax", "code"]
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# Working with code blocks
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\toc
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## Live evaluation of code blocks
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If you would like to show code as well as what the code outputs, you only need to specify where the script corresponding to the code block will be saved.
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Indeed, what happens is that the code block gets saved as a script which then gets executed.
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This also allows for that block to not be re-executed every time you change something _else_ on the page.
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Here's a simple example (change values in `a` to see the results being live updated):
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```julia:./exdot.jl
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using LinearAlgebra
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a = [1, 2, 3, 3, 4, 5, 2, 2]
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@show dot(a, a)
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println(dot(a, a))
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```
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You can now show what this would look like:
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\output{./exdot.jl}
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**Notes**:
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* you don't have to specify the `.jl` (see below),
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* you do need to explicitly use print statements or `@show` for things to show, so just leaving a variable at the end like you would in the REPL will show nothing,
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* only Julia code blocks are supported at the moment, there may be a support for scripting languages like `R` or `python` in the future,
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* the way you specify the path is important; see [the docs](https://tlienart.github.io/franklindocs/code/index.html#more_on_paths) for more info. If you don't care about how things are structured in your `/assets/` folder, just use `./scriptname.jl`. If you want things to be grouped, use `./group/scriptname.jl`. For more involved uses, see the docs.
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Lastly, it's important to realise that if you don't change the content of the code, then that code will only be executed _once_ even if you make multiple changes to the text around it.
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Here's another example,
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```julia:./code/ex2
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for i ∈ 1:5, j ∈ 1:5
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print(" ", rpad("*"^i,5), lpad("*"^(6-i),5), j==5 ? "\n" : " "^4)
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end
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```
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which gives the (utterly useless):
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\output{./code/ex2}
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note the absence of `.jl`, it's inferred.
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You can also hide lines (that will be executed nonetheless):
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```julia:./code/ex3
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using Random
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Random.seed!(1) # hide
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@show randn(2)
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```
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\output{./code/ex3}
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## Including scripts
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Another approach is to include the content of a script that has already been executed.
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This can be an alternative to the description above if you'd like to only run the code once because it's particularly slow or because it's not Julia code.
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For this you can use the `\input` command specifying which language it should be tagged as:
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\input{julia}{/_assets/scripts/script1.jl} <!--_-->
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these scripts can be run in such a way that their output is also saved to file, see `scripts/generate_results.jl` for instance, and you can then also input the results:
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\output{/_assets/scripts/script1.jl} <!--_-->
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which is convenient if you're presenting code.
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**Note**: paths specification matters, see [the docs](https://tlienart.github.io/franklindocs/code/index.html#more_on_paths) for details.
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Using this approach with the `generate_results.jl` file also makes sure that all the code on your website works and that all results match the code which makes maintenance easier.
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