# expr_parse.ludic - a condition, or/and/not, a comparison, sums and products, then a name
# with its members, indexes and calls
function px_cond(r: UiRd) -> UiExpr {
  let a = px_or(r)
  if not rd_op(r, "?") { return a }
  let e = ex_new(X_COND)
  e.a = a
  e.b = px_cond(r)
  if not rd_op(r, ":") { rd_fail(r, "':'") }
  e.c = px_cond(r)
  return e
}
function px_or(r: UiRd) -> UiExpr {
  var a = px_and(r)
  while rd_word(r, "or") or rd_op(r, "||") {
    let e = ex_new(X_OR)
    e.a = a
    e.b = px_and(r)
    a = e
  }
  return a
}
function px_and(r: UiRd) -> UiExpr {
  var a = px_not(r)
  while rd_word(r, "and") or rd_op(r, "&&") {
    let e = ex_new(X_AND)
    e.a = a
    e.b = px_not(r)
    a = e
  }
  return a
}
function px_not(r: UiRd) -> UiExpr {
  rd_ws(r)
  if rd_word(r, "not") or (rd_c(r, 0) == 33 and rd_c(r, 1) != 61 and rd_op(r, "!")) {
    let e = ex_new(X_NOT)
    e.a = px_not(r)
    return e
  }
  return px_cmp(r)
}
function px_bin(op: string, a: UiExpr, b: UiExpr) -> UiExpr {
  let e = ex_new(X_BIN)
  e.s = op
  e.a = a
  e.b = b
  return e
}
function px_cmp(r: UiRd) -> UiExpr {
  let a = px_sum(r)
  # literals, longest first: a list of them was made on every call
  if rd_op(r, "==") { return px_bin("==", a, px_sum(r)) }
  if rd_op(r, "!=") { return px_bin("!=", a, px_sum(r)) }
  if rd_op(r, "<=") { return px_bin("<=", a, px_sum(r)) }
  if rd_op(r, ">=") { return px_bin(">=", a, px_sum(r)) }
  if rd_op(r, "<") { return px_bin("<", a, px_sum(r)) }
  if rd_op(r, ">") { return px_bin(">", a, px_sum(r)) }
  return a
}
function px_sum(r: UiRd) -> UiExpr {
  var a = px_prod(r)
  while true {
    if rd_op(r, "+") { a = px_bin("+", a, px_prod(r)) } else if rd_op(r, "-") { a = px_bin("-", a, px_prod(r)) } else { return a }
  }
  return a
}
function px_prod(r: UiRd) -> UiExpr {
  var a = px_unary(r)
  while true {
    if rd_op(r, "*") { a = px_bin("*", a, px_unary(r)) } else if rd_op(r, "/") { a = px_bin("/", a, px_unary(r)) } else if rd_op(r, "%") { a = px_bin("%", a, px_unary(r)) } else { return a }
  }
  return a
}
function px_unary(r: UiRd) -> UiExpr {
  if rd_op(r, "-") {
    let e = ex_new(X_NEG)
    e.a = px_unary(r)
    return e
  }
  return px_post(r)
}
function px_post(r: UiRd) -> UiExpr {
  var a = px_primary(r)
  while r.err == "" {
    if rd_op(r, ".") {
      let e = ex_new(X_MEMBER)
      e.a = a
      e.s = rd_name(r)
      a = e
    } else if rd_op(r, "[") {
      let e = ex_new(X_INDEX)
      e.a = a
      e.b = px_cond(r)
      if not rd_op(r, "]") { rd_fail(r, "']'") }
      a = e
    } else { return a }
  }
  return a
}