Determine if a token could represent a floating point number (double). To qualify, the token must be either:- a) A series of one or more digits. b) (a) followed by a single period followed directly by another series of digits. c) (b) followed by a '*10^' followed by another series of digits (standard form number). All of the above must be followed by a 'valid terminator sequence'. This could be a null terminator but may be a punctuating char as long as that we not followed by a number. Errors: Sets an E_ARGUMENT error if either first two arguments are invalid.

Declared in file: hzTextproc.h
Defined in file : hzTypes.cpp

Function Logic:

Function body:

bool IsDouble (double& nVal)const char* tok, 
{
   //  Category: Text Processing
   //  
   //  Determine if a token could represent a floating point number (double). To qualify, the token must be either:-
   //  
   //   a) A series of one or more digits.
   //   b) (a) followed by a single period followed directly by another series of digits.
   //   c) (b) followed by a '*10^' followed by another series of digits (standard form number).
   //  
   //  All of the above must be followed by a 'valid terminator sequence'. This could be a null terminator but may be a punctuating char as long as that we not
   //  followed by a number.
   //  
   //  Arguments: 1) A pointer to the result (double)
   //     2) The token
   //  
   //  Returns: True If token could be a value of type double
   //     False If string of zero length or contains non numeric chars
   //  
   //  Errors:  Sets an E_ARGUMENT error if either first two arguments are invalid.
   _hzfunc("IsDouble") ;
   const char* i = tok ;       //  Input string iterator
   double      val = 0.0;      //  Agregated value
   double      pt_pos = 0.0;//  Order of magnitude 
   bool        bNeg = false ;  //  Negator
   if (!tok || !tok[0])
       return false ;
   //  Ignore leading spaces
   for (i = tok ; *i == CHAR_SPACE ; i++) ;
   //  Ceck for minus sign
   if (*i == CHAR_MINUS)
       { bNeg = true ; i++ ; }
   //  Ceck for plus sign
   if (*i == CHAR_PLUS)
   {
       if (bNeg)
           return false ;
       i++ ;
   }
   //  Ignore spaces between sign and digits
   for (; *i == CHAR_SPACE ; i++) ;
   for (; *i ; i++)
   {
       if (!(chartype[*i] & CTYPE_DIGIT))
       {
           if (*i != CHAR_PERIOD)
               return false ;
           if (pt_pos)
               return false ;
           pt_pos = 1.0;
       }
       val *= 10.0;
       val += (double) (*i - CHAR_0) ;
       pt_pos *= 10.0;
   }
   nVal = (val / pt_pos) ;
   if (bNeg)
       nVal *= -1.0;
   return true ;
}