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Merged
kkarbowiak merged 5 commits into from
Oct 3, 2025
Merged

Change conversion interface #164

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8dba9b8
Change signature of from_string function
kkarbowiak Oct 3, 2025
1ff438e
Adapt code in tutorial's custom1 example
kkarbowiak Oct 3, 2025
1cb77bc
Adapt code in tutorial's custom2 example
kkarbowiak Oct 3, 2025
6cdcadf
Adapt code in tutorial's custom3 example
kkarbowiak Oct 3, 2025
bf0aaf6
Update tutorial
kkarbowiak Oct 3, 2025
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20 changes: 12 additions & 8 deletions include/argparse.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -103,12 +103,17 @@ namespace argparse
class Converter
{
public:
auto from_string(std::string const & s, T & t) const -> bool
auto from_string(std::string const & s) const -> std::optional<T>
{
auto iss = std::istringstream(s);
auto t = T();
iss >> t;

return !iss.fail() && (iss.eof() || iss.peek() == std::istringstream::traits_type::eof());
if (!iss.fail() && (iss.eof() || iss.peek() == std::istringstream::traits_type::eof()))
{
return t;
}
return std::nullopt;
}

auto to_string(T const & t) const -> std::string
Expand All @@ -126,10 +131,10 @@ namespace argparse
};

template<typename T>
inline auto from_string(std::string const & s, T & t) -> bool
inline auto from_string(std::string const & s) -> std::optional<T>
{
auto const conv = Converter<T>();
return conv.from_string(s, t);
return conv.from_string(s);
}

template<typename T>
Expand Down Expand Up @@ -546,10 +551,9 @@ namespace argparse
}
else
{
auto value = T();
if (argparse::from_string(string, value))
if (auto const optvalue = argparse::from_string<T>(string); optvalue.has_value())
{
return std::any(value);
return std::any(*optvalue);
}
else
{
Expand Down Expand Up @@ -990,7 +994,7 @@ namespace argparse

static auto is_negative_number(std::string const & token) -> bool
{
if (auto num = double(); from_string(token, num))
if (auto const parsed = from_string<double>(token); parsed.has_value())
{
return true;
}
Expand Down
6 changes: 3 additions & 3 deletions test/unittest/custom.h
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Expand Up @@ -27,10 +27,10 @@ template<>
class Converter<foo::Custom>
{
public:
auto from_string(std::string const & s, foo::Custom & t) const -> bool
auto from_string(std::string const & s) const -> std::optional<foo::Custom>
{
t = foo::Custom(s);
return true;
auto t = foo::Custom(s);
return t;
}

auto to_string(foo::Custom const & t) const -> std::string
Expand Down
5 changes: 3 additions & 2 deletions tutorial/custom1.cpp
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Expand Up @@ -24,12 +24,13 @@ template<>
class Converter<geometry::Point>
{
public:
auto from_string(std::string const & s, geometry::Point & p) const -> bool
auto from_string(std::string const & s) const -> std::optional<geometry::Point>
{
std::istringstream iss(s);
auto p = geometry::Point();
char comma;
iss >> p.x >> comma >> p.y;
return true;
return p;
}

auto to_string(geometry::Point const & p) const -> std::string
Expand Down
7 changes: 5 additions & 2 deletions tutorial/custom2.cpp
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Expand Up @@ -24,12 +24,15 @@ template<>
class Converter<geometry::Point>
{
public:
auto from_string(std::string const & s, geometry::Point & p) const -> bool
auto from_string(std::string const & s) const -> std::optional<geometry::Point>
{
std::istringstream iss(s);
auto p = geometry::Point();
char comma;
iss >> p.x >> comma >> p.y;
return !iss.fail();
return !iss.fail()
? std::optional<geometry::Point>(p)
: std::nullopt;
}

auto to_string(geometry::Point const & p) const -> std::string
Expand Down
7 changes: 5 additions & 2 deletions tutorial/custom3.cpp
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Expand Up @@ -24,12 +24,15 @@ template<>
class Converter<geometry::Point>
{
public:
auto from_string(std::string const & s, geometry::Point & p) const -> bool
auto from_string(std::string const & s) const -> std::optional<geometry::Point>
{
std::istringstream iss(s);
auto p = geometry::Point();
char comma;
iss >> p.x >> comma >> p.y;
return !iss.fail();
return !iss.fail()
? std::optional<geometry::Point>(p)
: std::nullopt;
}

auto to_string(geometry::Point const & p) const -> std::string
Expand Down
21 changes: 14 additions & 7 deletions tutorial/readme.md
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Expand Up @@ -958,12 +958,13 @@ template<>
class Converter<geometry::Point>
{
public:
auto from_string(std::string const & s, geometry::Point & p) const -> bool
auto from_string(std::string const & s) const -> std::optional<geometry::Point>
{
std::istringstream iss(s);
auto p = geometry::Point();
char comma;
iss >> p.x >> comma >> p.y;
return true;
return p;
}

auto to_string(geometry::Point const & p) const -> std::string
Expand Down Expand Up @@ -1005,7 +1006,7 @@ optional arguments:
$ custom1 0,0 1,1
The distance is 1.41421
```
The return value of `argparse::Converter::from_string` indicates whether the conversion succeeded. You can use it to your advantage (`custom2.cpp`):
The `argparse::Converter::from_string` function should return an empty optional to indicate conversion failure. You can use it to your advantage (`custom2.cpp`):
```c++
#include "argparse.hpp"
#include <string>
Expand Down Expand Up @@ -1033,12 +1034,15 @@ template<>
class Converter<geometry::Point>
{
public:
auto from_string(std::string const & s, geometry::Point & p) const -> bool
auto from_string(std::string const & s) const -> std::optional<geometry::Point>
{
std::istringstream iss(s);
auto p = geometry::Point();
char comma;
iss >> p.x >> comma >> p.y;
return !iss.fail();
return !iss.fail()
? std::optional<geometry::Point>(p)
: std::nullopt;
}

auto to_string(geometry::Point const & p) const -> std::string
Expand Down Expand Up @@ -1110,12 +1114,15 @@ template<>
class Converter<geometry::Point>
{
public:
auto from_string(std::string const & s, geometry::Point & p) const -> bool
auto from_string(std::string const & s) const -> std::optional<geometry::Point>
{
std::istringstream iss(s);
auto p = geometry::Point();
char comma;
iss >> p.x >> comma >> p.y;
return !iss.fail();
return !iss.fail()
? std::optional<geometry::Point>(p)
: std::nullopt;
}

auto to_string(geometry::Point const & p) const -> std::string
Expand Down