css/css-syntax/anb-parsing.html

<!doctype html>
<title>An+B Parsing</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>

foo { color: blue; }

</style>

<meta name="author" title="Tab Atkins-Bittner">
<link rel=help href="https://drafts.csswg.org/css-syntax/#the-anb-type">

<script>

function roundtripANB(str) {
    const rule = document.styleSheets[0].cssRules[0];
    rule.selectorText = "foo";
    rule.selectorText = `:nth-child(${str})`;
    // Check for parse error.
    if(rule.selectorText == "foo") return "parse error";
    return rule.selectorText.slice(11, -1);
}
function testANB(input, expected) {
    test(()=>{
        assert_equals(roundtripANB(input), expected);
    }, `"${input}" becomes "${expected}"`);
}

/* Just going down all the syntax clauses one-by-one */
//  odd | even |
testANB("odd", "2n+1");
testANB("even", "2n");
//  <integer> |
testANB("1", "1");
testANB("+1", "1");
testANB("-1", "-1");
//
//  <n-dimension> |
testANB("5n", "5n");
testANB("5N", "5n");
//  '+'?† n |
testANB("+n", "n");
testANB("n", "n");
testANB("N", "n");
testANB("+ n", "parse error");
//  -n |
testANB("-n", "-n");
testANB("-N", "-n");
//
//  <ndashdigit-dimension> |
testANB("5n-5", "5n-5");
//  '+'?† <ndashdigit-ident> |
testANB("+n-5", "n-5");
testANB("n-5", "n-5");
testANB("+ n-5", "parse error");
//  <dashndashdigit-ident> |
testANB("-n-5", "-n-5");
//
//  <n-dimension> <signed-integer> |
testANB("5n +5", "5n+5");
testANB("5n -5", "5n-5");
//  '+'?† n <signed-integer> |
testANB("+n +5", "n+5");
testANB("n +5", "n+5");
testANB("+n -5", "n-5");
testANB("+ n +5", "parse error");
testANB("n 5", "parse error");
//  -n <signed-integer> |
testANB("-n +5", "-n+5");
testANB("-n -5", "-n-5");
testANB("-n 5", "parse error");
//
//  <ndash-dimension> <signless-integer> |
testANB("5n- 5", "5n-5");
testANB("5n- -5", "parse error");
testANB("5n- +5", "parse error");
testANB("-5n- 5", "-5n-5");
//  '+'?† n- <signless-integer> |
testANB("+n- 5", "n-5");
testANB("n- 5", "n-5");
testANB("+ n- 5", "parse error");
testANB("n- +5", "parse error");
testANB("n- -5", "parse error");
//  -n- <signless-integer> |
testANB("-n- 5", "-n-5");
testANB("-n- +5", "parse error");
testANB("-n- -5", "parse error");
//
//  <n-dimension> ['+' | '-'] <signless-integer>
testANB("5n + 5", "5n+5");
testANB("5n - 5", "5n-5");
testANB("5n + +5", "parse error");
testANB("5n + -5", "parse error");
testANB("5n - +5", "parse error");
testANB("5n - -5", "parse error");
//  '+'?† n ['+' | '-'] <signless-integer> |
testANB("+n + 5", "n+5");
testANB("n + 5", "n+5");
testANB("+ n + 5", "parse error");
testANB("+n - 5", "n-5");
testANB("+n + +5", "parse error");
testANB("+n + -5", "parse error");
testANB("+n - +5", "parse error");
testANB("+n - -5", "parse error");
//  -n ['+' | '-'] <signless-integer>
testANB("-n + 5", "-n+5");
testANB("-n - 5", "-n-5");
testANB("-n + +5", "parse error");
testANB("-n + -5", "parse error");
testANB("-n - +5", "parse error");
testANB("-n - -5", "parse error");

/* Swapped ordering is invalid */
testANB("1 - n", "parse error");
testANB("0 - n", "parse error");
testANB("-1 + n", "parse error");

/* Odd space usage */
testANB("2 n + 2", "parse error");
testANB("- 2n", "parse error");
testANB("+ 2n", "parse error");
testANB("+2 n", "parse error");

</script>