toy::FormatString< Args > Class Template Reference

Wrapper around a toy::CStringView pattern with consteval validation of placeholders. More...

Collaboration diagram for toy::FormatString< Args >:

Public Member Functions
consteval	explicit (false) FormatString(const CStringView &string) noexcept
	Validates string at compile time and stores it as a toy::CStringView.
	FormatString (const FormatString &other) noexcept=default
	Default copy constructor.
FormatString &	operator= (const FormatString &)=delete
	Copy assignment is deleted.
constexpr CStringView	get () const noexcept
	Returns the stored format pattern as a toy::CStringView.

Static Private Member Functions
static void	_compileTimeError (const char *message) noexcept
	Stub used when validation fails; the program should be ill-formed before a call is needed.

Private Attributes
const CStringView	_string
	The stored format string.

Detailed Description

template<class... Args>
class toy::FormatString< Args >

Wrapper around a toy::CStringView pattern with consteval validation of placeholders.

Two modes are supported, not mixed in one pattern: auto-indexed placeholders are exactly {}; positional placeholders are {0}, {1}, … (decimal digits only). {{ and }} are literal braces. In auto mode the number of {} must equal sizeof...(Args). In positional mode each index must be < sizeof...(Args); repeating an index is allowed and not every index need appear. Unmatched { or } makes construction ill-formed.

Template Parameters

Args	Template parameter pack representing the types of arguments that will be formatted.

Key Features

• Compile-time checks: consteval constructor; invalid patterns fail at compile time.
• Auto and positional modes: {} vs {N}; mixing both in one string is ill-formed.
• Storage: Holds a toy::CStringView to the pattern; no allocation.
• get(): Returns the same view; constexpr noexcept.

Usage Example

#include "core.hpp"
 
constexpr toy::FormatString<int, float> autoFmt(toy::CStringView("Value: {}, Float: {}"));
constexpr toy::FormatString<int, float> posFmt(toy::CStringView("Float: {1}, Value: {0}"));
 
// Ill-formed examples (do not compile):
// toy::FormatString<int, int>(toy::CStringView("{} {0}")); // mixed auto and positional
// toy::FormatString<int>(toy::CStringView("{"));           // unmatched brace

Performance Characteristics

• Construction: Work is done at compile time (consteval).
• get(): O(1); returns the stored toy::CStringView.

Safety Guarantees

• Invalid patterns: Diagnosed at compile time when the consteval constructor runs.
• Exception safety: All operations are noexcept; this type does not throw.

Compatibility

• C++23: consteval constructor and constexpr get() as implemented.
• CStringView: Pattern must be reachable as a const toy::CStringView at the call site.

See also

CStringView

Constructor & Destructor Documentation

FormatString()

template<class... Args>

toy::FormatString< Args >::FormatString ( const FormatString< Args > & other )

constevaldefaultnoexcept

Default copy constructor.

Parameters

other

FormatString to copy.

Member Function Documentation

_compileTimeError()

template<class... Args>

void toy::FormatString< Args >::_compileTimeError ( const char * message )

inlinestaticprivatenoexcept

Stub used when validation fails; the program should be ill-formed before a call is needed.

Parameters

message

Diagnostic text for implementations that surface it.

Note

Intended only from the consteval constructor path.

See also

FormatString(const CStringView &)

explicit()

template<class... Args>

toy::FormatString< Args >::explicit ( false ) const &

constevalnoexcept

Validates string at compile time and stores it as a toy::CStringView.

Parameters

string

Format pattern to validate and store.

Precondition

Braces in string are balanced; {{ and }} are literals.

Either: auto mode — number of {} equals sizeof...(Args); or positional mode — each {N} has N < sizeof...(Args), and the pattern does not mix {} with {N}.

Postcondition

The pattern is stored and can be read with get().

Note

consteval; ill-formed patterns make the program ill-formed.

Escaped {{ and }} are not placeholders.

See also

get()

get()

template<class... Args>

CStringView toy::FormatString< Args >::get ( ) const

nodiscardconstexprnoexcept

Returns the stored format pattern as a toy::CStringView.

Returns

The same view stored at construction time.

Note

constexpr; safe in constant evaluation.

See also

FormatString(const CStringView &)

operator=()

template<class... Args>

FormatString & toy::FormatString< Args >::operator= ( const FormatString< Args > & )

delete

Copy assignment is deleted.

Member Data Documentation

_string

template<class... Args>

const CStringView toy::FormatString< Args >::_string

private

The stored format string.

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The documentation for this class was generated from the following files:

• include/core/format_string.hpp
• include/core/format_string.inl