Discussion

BinarySearch takes sorted array info, and two subscripts,
fromLoc and toLoc, and item as arguments.  It returns false 
if item is not found in the elements info[fromLoc…toLoc].   
Otherwise, it returns true. 

BinarySearch can be written using iteration, or using recursion

base case

If remaining list has 0 elements (fromLoc > toLoc), there is no more processing to do.

general case

if ( item is stored at mid=(fromLoc+toLoc)/2 ) 
     return true;
else if (item < info[mid]) //recall sorted array
     return Binary Search from 0 to mid;
else
     return Binary Search from mid to toLoc;

       

Solution

template<class ItemType>
bool  BinarySearch   (  ItemType  info[ ] ,  ItemType  item , 
 		                 int fromLoc , int  toLoc ) 	
	// Pre: info [ fromLoc . . toLoc ] sorted in ascending order 
	// Post: Function value = ( item  in info [ fromLoc .. toLoc] ) 

{  int  mid ;
	 if  ( fromLoc > toLoc ) 	   //  base case -- not found
	           return  false ;                              
	 else {
         mid = ( fromLoc + toLoc ) / 2 ;
		  if ( info [ mid ] == item )  //base case-- found at mi  	    
              return  true  ;
         else if ( item < info [ mid ] )  // search lower half 
            return BinarySearch ( info, item, fromLoc, mid-1 ) ;
                     else            	// search upper half
		     return  BinarySearch( info, item, mid + 1, toLoc ) ;
         }           
}