CSE 109 Test 2  Wednesday  9 April 2003
<><><><><><><><><>SUGGESTED ANSWERS<><><><><><><><><>><><><><><>
1.  An Association is a pair consisting of a "key" and a "value." Write
the template class for Association so that the following code compiles and
produces the output indicated.  The class need have no other functionality.
 Association <int,double> a(2,2.7);
 Association <Word, Word> b("hope","esperanza");
 a.setValue(2.3);
 cout<<x<<" "<<b<<endl; // displays: {2, 2.3} {hope, esperanza}
================================================================
#include <fstream.h>

template <class KEY, class VALUE>
class Association
{public:
   Association(const KEY &k,const VALUE &v);
   void setValue(const VALUE &v);
 template <class K, class V>
 friend ostream & operator <<(ostream &out,const Association<K,V> & a);
 private:
   KEY key;
   VALUE value;
};

template <class KEY, class VALUE>
Association<KEY,VALUE>::Association(const KEY &k,const VALUE &v)
 :key(k),value(v){}

template <class KEY, class VALUE>
void Association<KEY,VALUE>::setValue(const VALUE &v)
 {value=v;}

template <class KEY, class VALUE>
ostream &operator <<(ostream &out,const Association<KEY,VALUE> &a)
{out<<"{"<<a.key<<", "<<a.value<<"}";
 return out;}
2.  Assume you are developing a parser for telephone numbers, e.g.,
(610)867-3136, and that you first want a tokenizer.  Write the declaration
and definitions for a class Token which reads input from cin and responds
to the member function next() by returning 0 for '(', 1 for ')', 2 for '-',
3 for a digit, 4 for a linefeed (eoln), and 5 for anything else (junk).  Your
tokenizer should consider blanks and tabs junk, i.e., no blanks or tabs are
allowed.
=======================================================================
class Token
{public:
  int next();
  static const int LPAR=0, RPAR=1, DASH=2, DIGIT=3, EOLN=4, JUNK=5;
 private:
  char ch;
};

int Token::next()
{switch(ch=cin.get())  //cin.get() returns -1 at eof()
  {case '(': return LPAR;
   case ')': return RPAR;
   case '-': return DASH;
   case '\n': return EOLN;
   default: if(ch>='0' && ch<='9')
             return DIGIT;
            else
              return JUNK;
  }
}

3.  Recalling the operations 0(add), 1(sub), 2(mul), 3(div), 4(cjump),
5(move), 6(push), 7(pop), assemble the following asm3 program, that is, write
the op3 code which corresponds to the given asm3 code.
     mov x, mem0                      5010000000
     add z, x, y                         4010005
     cjump v,v,v                      4006006006
   z var                                       0  ; any number will do
   y const 16                                 20
   v mov mem0,z                       5000004000
     cjump mem0, mem0, mem0           4000000000
   x var                              E           ; no number needed
   end                                2 3
   2 3

4.  Write a function "allEqual()" for which the following code returns true
if and only if the strings a, b, and c each contain the same characters.
The code should be resistant to crashing.
     char *a, *b, *c;
      //......  intervening code
     return allEqual(a,b,c);
 ====================================================================
 bool allEqual(char *a, char *b, char *c)
{return a==NULL && b==NULL && c==NULL ||
    a!=NULL && b!=NULL && c!=NULL && strcmp(a,b)==0 && strcmp(b,c)==0;
}