6.4 Solutions

1. mystery
2. a and b
3. int
4. function mystery (a, b : real) : int
5. If the first parameter is smaller than the second it returns -1, if it is bigger returns 1 and if they are equal it returns 0

% returns the argument that is smaller (comes first in ASCII)
function first (a, b : char) : char
   if a < b then
      result a
   else
      result b
   end if
end first

% returns true if the argument is an even number
% false if it is an odd number
function even (value : int) : boolean
   var temp : boolean := false
   if value mod 2 = 0 then
      temp := true
   end if
   result temp
end even

1. first and second
2. height and width
3. int
4. The height is 12 and the width is 8 They differ by: 4
5. It wouldn't make any difference. PosDiff finds the positive difference so it automatically subtracts the smaller argument from the bigger one.
6. ```
function posDiff (first, second : int) : int
   result abs(first - second)
end posDiff 
```
(c) is invalid because put is not a function. There is no result to store in x.
(d) is invalid because abs is a function. You need to do something with the result. You have to say put abs(x) or x := abs(x). You can't call it like a procedure.

% a
function ceiling (number : real) : int
   if number >= 0 then
      if round(number) = number then
        result round(number)
      else
        result round(number + 0.5)
      end if
   else
      if round(number) = number then
        result round(number)
      else
        result round(number - 0.5)
      end if
   end if
end ceiling

% b
put ceiling(3.1)
put ceiling(25.9)
put ceiling(67.0)
put ceiling(0.0)
put ceiling(-1.1)
put ceiling(-67.5)
put ceiling(-15.9)

function meanValue(a : array 1 .. * of int) : real
   var sum: int := 0
   
   for i : 1 .. upper(a)
      sum := sum + a(i)
   end for

   result sum / upper(a)
end meanValue

function smallest(a : array 1 .. * of real) : real
   var small: real := a(1)
   
   for i : 1 .. upper(a)
      if a(i) < small then
         small := a(i)
      end if
   end for

   result small
end smallest

% a
function numDigits(number : int) : int
    var count : int := 1
    var temp : int := number
    
    loop
       temp := temp div 10
       exit when temp = 0
       count := count + 1
    end loop
    
    result count
end numDigits

% b
var a : array 1 .. 6 of int
for i : 1 .. 6
    put "Enter number ", i, " of 6"
    get a(i)
end for

put "Number    Number of Digits"
put "--------------------------"
for i : 1 .. 6
    put a(i):6, numDigits(a(i)):12
end for