Nim Pattern Matching Example

pattern_matching.nim

#chokidar "*.nim" -c "nim js -r test.nim"
import patty
import jsconsole
import jsffi
import zero_functional
import templates

type
    Html* = object
        title*: cstring
        body*: cstring
    Markdown* = object
        body*: cstring

variant Content:
    HtmlKind(html: Html)
    MarkdownKind(markdown: Markdown)

proc htmlTemplate(html: Html): cstring = tmpli html"""
    <h1>$(html.title)</h1>
    <p>$(html.body)</p>
"""

proc markdownTemplate(markdown: Markdown): cstring = 
    # lets pretend it converts markdown
    return markdown.body

proc render(content: Content): cstring =
    match content:
        HtmlKind(html: html):
            result = htmlTemplate(html)
        MarkdownKind(markdown: markdown):
            result = markdownTemplate(markdown)

proc renderAll(contents: seq[Content]): cstring =
    return contents --> fold("".cstring, a & render(it))


var html: Content = HtmlKind(Html(title: "Hi there", body: "My body"))
var markdown: Content = MarkdownKind(Markdown(body: "# title"))

console.log(renderAll(@[html, markdown]))

# <h1>Hi there</h1>
# <p>My body</p>
# # title

zacyclic_variants.nim

import patty

type
    Dupes = enum
        Bro, Bros, Bra
    Beau {.acyclic.} = object
        case kind: Dupes
            of Bro, Bra:
                tada: string
            of Bros:
                bada: string
                bros: seq[Beau]
        lala: string 



proc show(x: Beau): void =
    match x:
        Bro(tada: tada, lala: lala):
            echo tada, " ", lala, " bro"
        Bra(tada: tada):
            echo tada, " bra"
        Bros(bada: bada, bros: bros):
            echo bada, " man"
            for bro in bros:
                show(bro)

var xy = Beau(kind: Bro, tada: "Yes", lala: "haha")

show(xy)

show(Beau(kind: Bra, tada: "yo"))

show(Beau(kind: Bros, bada: "yoyo", bros: @[xy]))