Ambiguity in operator [] Post: 302530190

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Top Forums Programming Ambiguity in operator [] Post 302530190 by 14341 on Monday 13th of June 2011 09:39:30 AM

06-13-2011

Registered User

Ambiguity in operator []

Hi All,

When i try to compile the following code for 64-bit it works, whereas for 32-bit version, Compiler barfs:

Code:

#include <iostream>
#include <string>

class String {
  public:
    String() { }
    String(const char* src) : myStr(src) { }
    String(const std::string& src) : myStr(src) { }
    String(const String& src) : myStr(src.myStr) { }

    operator const char*() const         { return myStr.c_str(); }
    char& operator[](size_t index)       { return myStr[index]; }
    char operator[] (size_t index) const { return myStr[index]; }

    size_t length() const { return myStr.length(); }
  private:
    std::string myStr;
};

int main() {
    String s("abcd");

    char c = s[1];

    std::cout << c << std::endl;

    return 0;
}

Code:

$ g++ -m32 -Wall -g ambiguous.cc
ambiguous.cc: In function ‘int main()’:
ambiguous.cc:23: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
ambiguous.cc:12: note: candidate 1: char& String::operator[](size_t)
ambiguous.cc:23: note: candidate 2: operator[](const char*, int) <built-in>

$ g++ -Wall -g ambiguous.cc
$./a.out
b

1) I cannot modify all the instances like, c = s[1]. There are hundreds of similar things in code.
2) operator const char* is required.

Could someone suggest any work-around, considering the above 2 points.

Thanks,
14341

---------- Post updated at 08:39 AM ---------- Previous update was at 08:38 AM ----------

Hi All,

Overloading the operator[], for all integer types (unsigned/signed) (int; long; long long) solved the problem.

Cheers,
14341

14341

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LEARN ABOUT CENTOS

std::decimal::decimal128

std::decimal::decimal128(3)				     Library Functions Manual				       std::decimal::decimal128(3)

NAME

       std::decimal::decimal128 -

SYNOPSIS

   Public Types
       typedef float __decfloat128 __attribute__ ((mode(TD)))

   Public Member Functions
       decimal128 (decimal32 d32)
       decimal128 (decimal64 d64)
       decimal128 (float __r)
       decimal128 (double __r)
       decimal128 (long double __r)
       decimal128 (int __z)
       decimal128 (unsigned int __z)
       decimal128 (long __z)
       decimal128 (unsigned long __z)
       decimal128 (long long __z)
       decimal128 (unsigned long long __z)
       decimal128 (__decfloat128 __z)
       __decfloat128 __getval (void)
       void __setval (__decfloat128 __x)
       decimal128 & operator*= (decimal32 __rhs)
       decimal128 & operator*= (decimal64 __rhs)
       decimal128 & operator*= (decimal128 __rhs)
       decimal128 & operator*= (int __rhs)
       decimal128 & operator*= (unsigned int __rhs)
       decimal128 & operator*= (long __rhs)
       decimal128 & operator*= (unsigned long __rhs)
       decimal128 & operator*= (unsigned long long __rhs)
       decimal128 & operator*= (long long __rhs)
       decimal128 & operator++ ()
       decimal128 operator++ (int)
       decimal128 & operator+= (int __rhs)
       decimal128 & operator+= (decimal32 __rhs)
       decimal128 & operator+= (decimal64 __rhs)
       decimal128 & operator+= (decimal128 __rhs)
       decimal128 & operator+= (unsigned int __rhs)
       decimal128 & operator+= (long __rhs)
       decimal128 & operator+= (unsigned long __rhs)
       decimal128 & operator+= (long long __rhs)
       decimal128 & operator+= (unsigned long long __rhs)
       decimal128 & operator-- ()
       decimal128 operator-- (int)
       decimal128 & operator-= (long __rhs)
       decimal128 & operator-= (int __rhs)
       decimal128 & operator-= (long long __rhs)
       decimal128 & operator-= (unsigned long long __rhs)
       decimal128 & operator-= (unsigned long __rhs)
       decimal128 & operator-= (decimal128 __rhs)
       decimal128 & operator-= (unsigned int __rhs)
       decimal128 & operator-= (decimal32 __rhs)
       decimal128 & operator-= (decimal64 __rhs)
       decimal128 & operator/= (decimal32 __rhs)
       decimal128 & operator/= (long long __rhs)
       decimal128 & operator/= (unsigned long long __rhs)
       decimal128 & operator/= (unsigned long __rhs)
       decimal128 & operator/= (decimal64 __rhs)
       decimal128 & operator/= (unsigned int __rhs)
       decimal128 & operator/= (decimal128 __rhs)
       decimal128 & operator/= (long __rhs)
       decimal128 & operator/= (int __rhs)

Detailed Description
       3.2.4 Class decimal128.

       Definition at line 393 of file decimal.

Constructor &; Destructor Documentation
   std::decimal::decimal128::decimal128 (__decfloat128__z) [inline]
       Conforming extension: Conversion from scalar decimal type.

       Definition at line 418 of file decimal.

Author
       Generated automatically by Doxygen for libstdc++ from the source code.

libstdc++							  Tue Jun 10 2014				       std::decimal::decimal128(3)

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