STACK-JS custom syntax example This question shows one can use client-side JavaScript to pre-process the answer and thus allow custom syntax, like operators. This is largely inspired by the issue #938. What we do is as follows:

  1. We have some magical operator like a £ b that maps to a function like pound(a,b). But we do not and cannot define it as an operator on the CAS side.
  2. On the CAS side we have two things, firstly a `texput` rule rendering that function as an operator. And secondly, something that turns the teacher's answer into a string where we map that function into operator-like syntax.
  3. We then have a hidden algebraic input ans1 with a visible validation and the special option of hideanswer to stop the teachers answer from being shown. This will be the input that goes into PRTs. The teacher's answer for this will be the function form of the correct answer.
  4. What the student acts on is a secondary string type input ans1b which has no validation and no direct role in PRTs. The teacher's answer for this will be the operator form of the correct answer.
  5. Finally, we will have a [[escape]][[javascript]]][[/escape]]-block that listens to ans2 for changes parses it and converts it to the function format to be pushed into ans1.

[[input:ans1]][[input:ans2]] [[validation:ans1]]

[[validation:ans2]] [[javascript input-ref-ans1="trg" input-ref-ans2="src"]] const t = document.getElementById(trg); const s = document.getElementById(src); s.addEventListener('change', () => { if (s.value.indexOf("£") !== -1) { /* This is a place for a proper parser to do operator precedence-related things * but for this demo lets assume a shallow expression and that the binding of * this operator is so high that nothing escapes it. */ t.value = "pound(" + s.value.split("£").join(",") + ")"; t.dispatchEvent(new Event('change')); } else { t.value = s.value; t.dispatchEvent(new Event('change')); } return true; }); [[/javascript]]]]> 1 0.1 0 2023043000 [[feedback:prt1]] 0 0 0 . dot 0 i cos-1 lang ans1 algebraic ta 10 1 0 0 pound 0 0 0 1 2 ans2 string taop 10 1 0 0 0 0 0 0 0 prt1 1.0000000 1 0 0 AlgEquiv ans1 ta 0 = 1 -1 prt1-1-T {#ans1#}]]> = 0 -1 prt1-1-F {#ans1#}]]>