Recursion in (and out) of Gotempl 🧑‍🧒‍🧒

Something epic you can do with golang templates is recursion. Here's a cool example from 2023 I wrote while writing my old blog in golang templates.

Assuming you have the following struct:

type Inode struct {
        Filename string
        Path     string
        IsDir    bool
        Children []Inode
}

You can use go's standard html/templates library to define a template that calls itself to make a bulleted list of the file tree you're scanning:

{{ define "ulRecursion" }}
    <li>
        {{if .IsDir }}
            <strong>{{ .FileName }}</strong>
        {{ else }}
            <a href="{{ .Path }}">{{ .FileName }}</a>
        {{ end }}

        {{ if gt (len .Children) 0 }}
            <ul>
              {{ range .Children }}
              {{ template "ulRecursion" . }}
              {{ end }}
            </ul>
        {{ end }}
    </li>
{{ end }}

To get the following out:

Figure 1: gotempl bulleted list of filesystem

You can use it for whatever hierarchical structure you wanna represent. Make your own tree(1), a comments/replies section for your blog, a family tree graph. The world is your oyster…

…But not really. Anything that can define itself, that has a self-propagating desire whether that be our genes or opinions or technology, you can understand with some kind of recursive process. Humans do their best to match their own theories, but Genghis Khan's progeny can't match the capacity of a 9front filesystem.

bust of tamerlane facing forward — Figure 2: Tamerlane, last of the steppe conquerors, never reached the multiplicative power of Glenda, the Plan 9 Bunny

glenda the plan9 bunny with a space helmet — Figure 2: Tamerlane, last of the steppe conquerors, never reached the multiplicative power of Glenda, the Plan 9 Bunny

What you can do is understand these processes, learn where you descend from, notice the curves, read SICP, pinpoint what you're converging towards as you're swirling about infinitely… 🌀