Function skeletonize

src/compute-engine/rubi/compile.ts:61–70

Replace Blank/BlankOptional atoms with placeholder symbols.

(expr: Json, variable: string)

const VAR = 'RUBIPATVARX';

function isCall(x: Json, op: string): x is Json[] {
  return Array.isArray(x) && x[0] === op;
}

/** Replace Blank/BlankOptional atoms with placeholder symbols. */
function skeletonize(expr: Json, variable: string): Json {
  if (isCall(expr, 'Blank') || isCall(expr, 'BlankOptional')) {
    const name = expr[1] as string;
    if (name === variable) return VAR;
    return (expr[0] === 'BlankOptional' ? OPT : SLOT) + name;
  }
  if (Array.isArray(expr))
    return expr.map((a, i) => (i === 0 ? a : skeletonize(a, variable))) as Json;