User Guide

User Guide

So how do we highlight source code using the Highlights package?

Firstly we import the package โ€“ assuming it has already been installed following the guidelines found in Installation.

using Highlights

This will make several names available to us for use:

Next we need a String to highlight. For this example we will be using the code sample from The Julia Language website.

source =
    function mandel(z)
        c = z
        maxiter = 80
        for n = 1:maxiter
            if abs(z) > 2
                return n-1
            z = z^2 + c
        return maxiter

    function randmatstat(t)
        n = 5
        v = zeros(t)
        w = zeros(t)
        for i = 1:t
            a = randn(n,n)
            b = randn(n,n)
            c = randn(n,n)
            d = randn(n,n)
            P = [a b c d]
            Q = [a b; c d]
            v[i] = trace((P.'*P)^4)
            w[i] = trace((Q.'*Q)^4)
        std(v)/mean(v), std(w)/mean(w)

To highlight source we pass it to highlight along with the output stream, the required output format, the lexer, and, optionally, the theme.

open("source.html", "w") do stream
    highlight(stream, MIME("text/html"), source, Lexers.JuliaLexer)

This will print the highlighted version of source to source.html using the JuliaLexer definition and the DefaultTheme. We can also output $\LaTeX$ formatted text by using MIME("text/latex") instead.

Note though that at this point we have not included any style information needed to colourise and typeset the text that highlight has printed to the file. For that we need to call stylesheet first as follows:

open("source.html", "w") do stream
    stylesheet(stream, MIME("text/html"))
    highlight(stream, MIME("text/html"), source, Lexers.JuliaLexer)

The highlighted version of source is available from here.

stylesheet is passed most of the same information that highlight is aside from the source.


The above example will not produce a complete HTML page. No <html>, <head>, or <body> are printed. This is left to the user to decide what approach would suit their usecase best.

Also note that if you would like to print the stylesheet to a .css file rather than to the same index.html then you may use:

open("theme.css", "w") do stream
    stylesheet(stream, MIME("text/css"))

That's all there is to it. Have a look at the Theme Guide and Lexer Guide if you would like to define your own themes and lexers. Please consider contributing any that you write back to the package so that all users can benefit from them โ€“ no lexer or theme is too obscure to include in Highlights!