maybe_error.cpp

Tests if any of the expected args passed in has an error.

Parameters

[in]

The

tl::expected<T, E> variables. All have to use the same error type.

Template Parameters

E	The error type
Args	The value types for the tl::expected<T, E> args

Returns

The first error found or nothing

// Copyright 2022 Tyler Weaver
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#include <fp/all.hpp>
 
namespace views = ::ranges::views;
 
fp::Result<double> divide_4_by(double x) {
  if (x == 0.0) {
    return tl::make_unexpected(fp::InvalidArgument(fmt::format("divide by 0")));
  }
  return 4.0 / x;
}
 
fp::Result<double> f1(double x) { return divide_4_by(x); }
fp::Result<double> f2(double x) { return divide_4_by(x); }
fp::Result<double> f3(double x) { return divide_4_by(x); }
fp::Result<double> f4(double x) { return divide_4_by(x); }
 
fp::Result<double> do_work() {
  auto const a = fp::make_result(2.4) | f1 | f2;
  auto const b = fp::make_result(0.0) | f3 | f4;
 
  if (auto const error = fp::maybe_error(a, b); error) {
    return tl::make_unexpected(*error);
  }
 
  return *a + *b;
}
 
int main() {
  auto const result = do_work();
  fmt::print("result: {}\n", result);
  // result: [Result<T>: [Error: [InvalidArgument] divide by 0]]
 
  return 0;
}