Difference between _ttof, atof, _atof_l, _wtof, _wtof_l in C++ and C?
Here's the translation and explanation of the differences between _ttof, atof, _atof_l, _wtof, and _wtof_l in C++ and C, focusing on string conversion functions:
Differences Between _ttof, atof, _atof_l, _wtof, and _wtof_l in C++ and C
These functions are used to convert strings to floating-point numbers, and they vary in terms of the types of input they handle and their specific use cases.
1.) Key Functions:
1. _ttof
- Purpose
: Converts a string to a floating-point number.
- Input
: Handles both narrow (ANSI) and wide (Unicode) character strings based on the _UNICODE macro definition.
- Defined in
: <tchar.h>.
- Usage
: Adaptable between ANSI and Unicode environments.
2. atof
:
- Purpose
: Converts a C-style string (null-terminated) to a double.
- Input
: Narrow character strings (char*).
- Usage
: Standard function for converting a string to a floating-point number in C/C++.
3. _atof_l
:
- Purpose
: Converts a string to a floating-point number using a specified locale.
- Input
: Narrow character strings (char*).
- Locale
: Allows conversion according to locale-specific decimal separators.
- Usage
: Useful when dealing with locale-specific number formats.
4. _wtof
:
- Purpose
: Converts a wide-character string (wchar_t*) to a double.
- Input
: Wide-character strings (wchar_t*).
- Usage
: For Unicode (wide character) strings.
5. _wtof_l
:
- Purpose
: Converts a wide-character string to a floating-point number using a specified locale.
- Input
: Wide-character strings (wchar_t*).
- Locale
: Allows conversion according to locale-specific decimal separators for wide characters.
- Usage
: Useful for locale-specific formatting with wide-character strings.
2.) Example Usage:
#include <tchar.h>#include <cstdlib>#include <cwchar>#include <locale>// Conversion from CString to intCStringstrText=_T("123");intn=_ttoi(strText);// Convert to an integer// Result: n = 123// Conversion from CString to doubleCStringstrText=_T("123.456");// Convert to a floating-point numberdoubled=_ttof(strText);// Result: d = 123.456// Conversion using atof// Convert to doubledoubleatofValue=atof("33.364");// Result: atofValue = 33.364// Conversion using _wtof// Convert wide-character string to doubledoublewideValue=_wtof(L"333.64");// Result: wideValue = 333.64// Conversion with locale settings// Set locale to Germansetlocale(LC_NUMERIC,"de_DE");// Convert with German decimal separatordoublegermanValue=atof("123,456");// Result: germanValue = 123.456// Conversion with locale settings using _atof_l// French localelocale_tfrenchLocale=newlocale(LC_ALL_MASK,"fr_FR",(locale_t)0);// Convert with French decimal separatordoublefrenchValue=_atof_l(" -2,309e-25",frenchLocale);// Result: frenchValue = -2.309e-25
3.) Explanation:
- _ttoi and _ttof
: These functions are macros that adapt to either ANSI or Unicode based on the _UNICODE macro. They are used with CString, which is part of MFC (Microsoft Foundation Classes).
- atof
: Standard C function for converting narrow character strings to floating-point numbers.
- _atof_l
: Allows conversion of strings to floating-point numbers with locale-specific decimal separators.
- _wtof
: Used for converting wide-character strings to floating-point numbers.
- _wtof_l
: Allows conversion of wide-character strings with locale-specific formatting.
4.) Notes:
- Locale Handling
: Functions like _atof_l and _wtof_l handle locale-specific decimal separators, making them suitable for international applications where number formats vary.
- Backward Compatibility
: Functions such as atoi(), atol(), and atof() are part of the standard library and have been around for a long time, providing backward compatibility.
This guide provides a comprehensive overview of these functions and how they can be used to handle string-to-number conversions in C++ and C, accommodating different character types and locale settings.
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