Convert String to Integer With Error-Checking

[TheNoviceDev]

I want to convert a string to an integer and validate that it is an actual integer. The following is what I have. An extra pair of eyes can help me locate a possible validation error I didn't check for or a way to accomplish the same tasks but in a better way. Err_Type is an enumeration of different types of errors. All ideas are appreciated. Just trying to better my understanding of c++.

int StrToInt(string str, Err_Type* err, int base)               
{
    int Result = 0;                                             
    *err = NO_ERR;                                              
    // Makes sure string isn't empty
    Str_RemoveChar(&str, ' ');                                  
    if (str.empty())                                            
    {
        *err = EMPTY;                                           
        return 0;                                               
    }
    // Gets number of negative signs
    int Negs = 0;                                               
    for (int i = 0; i < str.length(); i++)                      
    {
        if (str[i] == '-') Negs++;                              
        else break;                                             
    }
    // Makes sure string doesn't contain solely negative signs  
    if (!(Negs - str.length()))                                 
    {
        *err = INVALID_INPUT;                                   
        return 0;                                               
    }
    // Sets the sign of the number
    str = str.substr(Negs);                                     
    if (Negs % 2)                                               
        str = "-" + str;                                        
    // Tests the conversion of the string
    size_t idx = 0;                                             
    try {
        Result = stoi(str, &idx, base);                         
    }
    catch (invalid_argument)                                    
    {
        *err = INVALID_INPUT;                                   
        return 0;                                               
    }
    catch (out_of_range)                                        
    {
        *err = OUT_OF_RANGE;                                    
        return 0;                                               
    }
    if (idx != str.length())                                    
    {
        *err = INVALID_INPUT;                                   
        return 0;                                               
    }
    return Result;                                              
}

[Mantorr22]

I want to convert a string to an integer and check for all possible errors. The following is what I have. An extra pair of eyes can help me locate a possible error I didn't check for or a way to accomplish the same tasks but in a better way.

I am not clear what you are asking. What is the specific error are you encountering? Or are you asking for a code review?

[TheNoviceDev]

No sorry, I meant I was wanting to check for all possible input errors. user enters a math problem (ex: "12+7*-32"). I parse this string into a vector of strings that alternate between numeric and operator. I need to check each numeric by attempting to convert them to integers. I am asking for a code review. I am basically trying to write the best function to validate and convert a string to an integer to be used for current and future projects. Learning through the advice of the general public :)

[JLBorges]

If we must use error codes rather than return values exceptions, I may write something like this:

std::string trim( std::string str ) // remove leading, trailing space
{
    while( !str.empty() && std::isspace( str.back() ) ) str.pop_back() ;

    std::size_t pos = 0 ;
    while( pos < str.size() && std::isspace( str[pos] ) ) ++pos ;
    return str.substr(pos) ;
}

std::string collapse_sign( std::string str ) // collapse leading sign
{
    const auto pos = str.find_first_not_of( "+-" ) ;

    if( pos != std::string::npos )
    {
        bool neg = false ;
        for( std::size_t i = 0 ; i < pos ; ++i ) if( str[i] == '-' ) neg = !neg ;

        return ( neg ? "-" : "" ) + str.substr(pos) ;
    }

    else return "-" ; // all + or -  (this will result in invalid input)
}

std::string clean( std::string str ) { return collapse_sign( trim(str) ) ; }

enum class s2i { OK, EMPTY, INVALID_INPUT, OUT_OF_RANGE, INVALID_BASE } ;

std::ostream& operator<< ( std::ostream& stm, s2i status )
{
    static const std::string name[] { "OK", "EMPTY", "INVALID_INPUT", "OUT_OF_RANGE", "INVALID_BASE" } ;
    return stm << name[ int(status) ] ;
}

s2i str_to_int( std::string str, int& result, int base )
{
    result = 0 ;

    if( base < 0 || base > 36 ) return s2i::INVALID_BASE ;
    else if( str.empty() ) return s2i::EMPTY ;

    else try
    {
        str = clean(str) ;
        std::size_t pos = 0 ;
        result = std::stoi( str, std::addressof(pos), base ) ;
        if( pos == str.size() ) return s2i::OK ;
        else { result = 0 ; return s2i::INVALID_INPUT ; }
    }

    catch( const std::out_of_range& ) { return s2i::OUT_OF_RANGE ; }
    catch( const std::exception& ) { return s2i::INVALID_INPUT ; }
}

http://coliru.stacked-crooked.com/a/2bb01e8de91e9b65

[TheNoviceDev]

Thank you. You've made me rethink some of my logic and clean up my code some more. thank you very much.