Function ExpandExistsOneMacro

parser/macro.cc:151–181

}

absl::optional<Expr> ExpandExistsOneMacro(MacroExprFactory& factory,
                                          Expr& target, absl::Span<Expr> args) {
  if (args.size() != 2) {
    return factory.ReportError("exists_one() requires 2 arguments");
  }
  if (!args[0].has_ident_expr() || args[0].ident_expr().name().empty()) {
    return factory.ReportErrorAt(
        args[0], "exists_one() variable name must be a simple identifier");
  }
  if (args[0].ident_expr().name() == kAccumulatorVariableName) {
    return factory.ReportErrorAt(
        args[1], absl::StrCat("exists_one() variable name cannot be ",
                              kAccumulatorVariableName));
  }
  auto init = factory.NewIntConst(0);
  auto condition = factory.NewBoolConst(true);
  auto accu_ident = factory.NewAccuIdent();
  auto const_1 = factory.NewIntConst(1);
  auto inc_step = factory.NewCall(CelOperator::ADD, std::move(accu_ident),
                                  std::move(const_1));

  auto step = factory.NewCall(CelOperator::CONDITIONAL, std::move(args[1]),
                              std::move(inc_step), factory.NewAccuIdent());
  accu_ident = factory.NewAccuIdent();
  auto result = factory.NewCall(CelOperator::EQUALS, std::move(accu_ident),
                                factory.NewIntConst(1));
  return factory.NewComprehension(args[0].ident_expr().name(),
                                  std::move(target), factory.AccuVarName(),
                                  std::move(init), std::move(condition),
                                  std::move(step), std::move(result));
}

Macro MakeExistsOneMacro() {
  auto status_or_macro =