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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alter_operator

ALTER 
OPERATOR(7)						   SQL Commands 						 ALTER OPERATOR(7)

NAME

       ALTER OPERATOR - change the definition of an operator

SYNOPSIS

       ALTER OPERATOR name ( { lefttype | NONE } , { righttype | NONE } ) OWNER TO newowner

DESCRIPTION

       ALTER OPERATOR changes the definition of an operator. The only currently available functionality is to change the owner of the operator.

       You  must own the operator to use ALTER OPERATOR.  To alter the owner, you must also be a direct or indirect member of the new owning role,
       and that role must have CREATE privilege on the operator's schema. (These restrictions enforce that altering the owner doesn't do  anything
       you couldn't do by dropping and recreating the operator.  However, a superuser can alter ownership of any operator anyway.)

PARAMETERS

       name   The name (optionally schema-qualified) of an existing operator.

       lefttype
	      The data type of the operator's left operand; write NONE if the operator has no left operand.

       righttype
	      The data type of the operator's right operand; write NONE if the operator has no right operand.

       newowner
	      The new owner of the operator.

EXAMPLES

       Change the owner of a custom operator a @@ b for type text:

       ALTER OPERATOR @@ (text, text) OWNER TO joe;

COMPATIBILITY

       There is no ALTER OPERATOR statement in the SQL standard.

SEE ALSO

       CREATE OPERATOR [create_operator(7)], DROP OPERATOR [drop_operator(7)]

SQL - Language Statements					    2010-05-14							 ALTER OPERATOR(7)

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