Typst: To get the version of Typst in use

tcversion.typ

// Typst version as int array, such as (0, 11, 0).
#let version = {
  // >=0.9.0 : gets exact version
  // <0.9.0 : error (sys.version is undefined)
  let sys-version() = {
    array(sys.version)
  }
  // checks whether chr is a valid counting symbol
  let check-by-numbering(chr) = {
    "B" not in str(numbering(chr + "A", 2, 1))
  }

  // 0.9.0, 0.10.0 : true (str(-1) == "\u{2212}1")
  // <0.9.0 : false (str(-1) == "-1")
  let check-v9() = {
    "\u{2212}" in str(-1)
  }
  // >=0.8.0 : true (type != str)
  //  <0.8.0 : false ("string" == "string")
  let check-v8() = {
    type(type(1)) != type("1")
  }
  // 0.7.0 : true
  // ("11. B" stays in inner list, so len() == 2)
  // 0.5.0, 0.6.0 : false 
  // ("11. B" stays in outer list, so len() == 4)
  let check-v7() = {
    let it = [
1. A
  1. A
 11. B]
    it.children.len() < 4
  }
  // 0.6.0, 0.7.0 : true
  // ("1/2!" is parsed as 1/(2!), so the entity is a frac)
  // 0.5.0 : false 
  // ("1/2!" is parsed as (1/2)!)
  let check-v6() = {
    ($1/2!$).body.func() == math.frac
  }
  // 0.4.0 : true (math.ast is U+2217)
  // 0.2.0, 0.3.0 : false (math.ast is U+002A)
  let check-v4() = {
    str(math.ast.op) == str(math.ast)
  }
  // 0.3.0, 0.4.0 : true (math.dot is U+22C5)
  // 0.2.0 : false (math.dot is U+002E)
  let check-v3() = {
    str(math.dot.op) == str(math.dot)
  }

  // sequence for version detection
  if check-v8() {
    let v11 = check-by-numbering("\u{3042}")
    if v11 or check-v9() {
      sys-version()
    } else {
      (0, 8, 0)
    }
  } else {
    let v1 = check-by-numbering("\u{5D0}")
    let v2 = check-by-numbering("\u{3044}")
    let v5 = check-by-numbering("\u{AC00}")
    if v5 {
      if check-v7()      { (0, 7, 0) }
      else if check-v6() { (0, 6, 0) }
      else               { (0, 5, 0) }
    } else if v2 {
      if check-v4()      { (0, 4, 0) }
      else if check-v3() { (0, 3, 0) }
      else               { (0, 2, 0) }
    } else {
      if v1 { (0, 1, 0) }
      else  { (0, 0, 0) } // before 0.1.0
    }
  }
}

test.typ

#import "tcversion.typ"
This is Typst version
// tcversion.version is an int array.
#tcversion.version.map(str).join(".");.