Vix.cpp

Appearance

to_int ​

to_int parses a base-10 integer from a string, with strict validation and overflow checks.

It is part of vix::conversion and returns an expected<T, ConversionError>.

cpp
#include <vix/conversion/ToInt.hpp>

What it does ​

Rules implemented by to_int<T>():

  • Input is ASCII-trimmed (leading and trailing whitespace removed)
  • Optional leading + or -
  • At least one digit is required
  • The entire trimmed input must be numeric (no trailing characters)
  • Overflow and underflow are detected for the target type

API ​

Generic parser ​

cpp
template <typename Int>
expected<Int, ConversionError> to_int(std::string_view input) noexcept;

Constraints:

  • Int must be an integral type (std::is_integral_v<Int>)

Convenience helpers ​

cpp
expected<int,        ConversionError> to_int32 (std::string_view input) noexcept;
expected<std::int64_t, ConversionError> to_int64 (std::string_view input) noexcept;

expected<unsigned,      ConversionError> to_uint32(std::string_view input) noexcept;
expected<std::uint64_t, ConversionError> to_uint64(std::string_view input) noexcept;

Error behavior ​

On failure, to_int returns make_unexpected(ConversionError{...}).

Typical error codes:

  • EmptyInput if the trimmed input is empty
  • InvalidCharacter if a non-digit appears where a digit is expected
  • TrailingCharacters if extra characters remain after the number
  • Overflow or Underflow if the value does not fit the target type

Note: the parser uses the trimmed view to parse, but preserves the original input inside the returned ConversionError to improve diagnostics upstream.

Examples ​

Parse signed integer ​

cpp
#include <vix/conversion/ToInt.hpp>
#include <iostream>

using vix::conversion::to_int;

void example_basic()
{
  auto r = to_int<int>("  -42  ");
  if (!r)
  {
    std::cout << "error: " << r.error().message() << "\n";
    return;
  }

  std::cout << "value: " << r.value() << "\n";
}

Reject trailing characters ​

cpp
#include <vix/conversion/ToInt.hpp>
#include <iostream>

using vix::conversion::to_int;

void example_trailing()
{
  auto r = to_int<int>("12px");
  if (!r)
  {
    // TrailingCharacters
    std::cout << r.error().message() << "\n";
    return;
  }
}

Parse unsigned integer ​

cpp
#include <vix/conversion/ToInt.hpp>
#include <iostream>

using vix::conversion::to_uint64;

void example_unsigned()
{
  auto r = to_uint64("18446744073709551615");
  if (!r)
  {
    std::cout << "error: " << r.error().message() << "\n";
    return;
  }

  std::cout << "value: " << r.value() << "\n";
}

Overflow detection ​

cpp
#include <vix/conversion/ToInt.hpp>
#include <iostream>

using vix::conversion::to_int32;

void example_overflow()
{
  auto r = to_int32("999999999999");
  if (!r)
  {
    // Overflow
    std::cout << r.error().message() << "\n";
    return;
  }
}

Tips ​

  • Prefer the typed helpers (to_int32, to_uint64, etc.) when your intent is fixed.
  • If you need different bases (hex, octal) or relaxed parsing, implement a separate parser to keep this one strict and predictable.