# 関数の定義は誰でもできる
def max( x, y ) 
  if  x >= y then
    return x
  else 
    return y
  end
end

i = 3; j = 5
x = max( i, j )
puts( "#{x} is the maximum of #{i} and #{j}" )

# 関数の定義と呼び出し�@
def max( x, y ) 
  if  x >= y then
    return x
  else 
    return y
  end
end

i = 3; j = 5
x = max( i, j )
puts( "#{x} is the maximum of #{i} and #{j}" )

i = 10; j = 15
x = max( i, j )
puts( "#{x} is the maximum of #{i} and #{j}" )

i = 5; j = -9
x = max( i, j )
puts( "#{x} is the maximum of #{i} and #{j}" )

# 関数の定義と呼び出し�A
def f( x, y )
  z = x*x+y*y
  return z
end

(0..9).each{ |x|
	(0..9).each{ |y|
		print( " x = " , x , " y= " , y , " f= " , f( x , y ) , "\n" )
	}
}

# 関数の定義と呼び出し�B
def f( x, y, z )
  w = x*x+y*y+z*z
  return w
end

(0..9).each{ |x|
	(0..9).each{ |y|
		(0..9).each{ |z|
		print( " x = " , x , " y= " , y , " z= " , z , " f= " , f( x , y , z ) , "\n" )
		}
	}
}

# 2数の最小値を値とする関数
def min( x, y) 
  if  x <= y then
    return x
  else 
    return y
  end
end

i = 3; j = 5
x = min( i, j )
puts( "#{x} is the minimum of #{i} and #{j}" )

# 3数の最大値を値とする関数
def max( x, y, z ) 
  if ( x >= y ) then
    if ( y >= z ) then
      return x
    else 
      if ( x >= z ) then
        return x
      else 
        return z
      end
    end
else 
    if ( x >= z ) then 
      return y
    else 
      if ( y >= z ) then 
        return y
      else
        return z
      end
    end
  end
end

i = 3; j = 5; k = 7
x = max( i, j, k )
puts( "#{x} is the maximum of #{i}, #{j}, and #{k}" )

# 関数が複数個定義されている場合
def max( x, y) 
  if  x >= y then
    return x
  else 
    return y
  end
end
def min( x, y) 
  if  x <= y then
    return x
  else 
    return y
  end
end

i = 3; j = 5
puts( "#{max( i, j )} is the maximum of #{i} and #{j}" )
puts( "#{min( i, j )} is the minimum of #{i} and #{j}" )

# 関数は関数を使えるか？�@
def max2( x, y) 
  if  x >= y then
    return x
  else 
    return y
  end
end

def max3( x, y, z ) 
  return max2( x, max2( y, z) )
end

i = 3; j = 5; k = 7
puts( "#{max2( i, j )} is the maximum of #{i} and #{j}" )
puts( "#{max3( i, j, k )} is the maximum of #{i}, #{j}, and #{k}" )

# 関数は関数を使えるか？�A
def max2( x, y) 
  if  x >= y then
    return x
  else 
    return y
  end
end

def max4( x, y, z, u ) 
  return max2( max2( x, y) , max2( z, u) )
end

i = 3; j = 5; k = 7; l = 9 
puts( "#{max2( i, j )} is the maximum of #{i} and #{j}" )
puts( "#{max4( i, j, k, l )} is the maximum of #{i}, #{j}, #{k}, and #{l}" )

# （注意!）変数に値を戻すことはできない�@
def f( x , y )
	x = x + 1
	y = y + 1
end

a = 3
b = 5
print( " a = " , a , " " , " b= " , b , "\n" )
f( a , b )
print( " a = " , a , " " , " b= " , b , "\n" )

# （注意!）変数に値を戻すことはできない�A
def f( x , y )
	x = x + 1
	y = y + 1
end

x = 3
y = 5
print( " x = " , x , " " , " y= " , y , "\n" )
f( x , y )
print( " x = " , x , " " , " y= " , y , "\n" )

# 戻り値のない関数
def sayHello( n ) 
  n.times{ |i| 
     i.times{ 
　　   print( " " )
     }
     puts( "Hello!" )
  }
end

sayHello( 4 )

# 戻り値のない関数の例�@
def max( x, y )
  if  x >= y then
    z = x
  else 
    z = y
  end
  puts( "#{z} is the maximum of #{x} and #{y}" )
end

i = 3; j = 5
max( i, j )

i = 9; j = 15
max( i, j )

i = -5; j = -7
max( i, j )

# 戻り値のない関数の例�A
def max( x, y )
  if  x >= y then
    z = x
  else 
    z = y
  end
  puts( "#{z} is the maximum of #{x} and #{y}" )
end

i = 3; j = 5
k = max( i, j )
print( " k= " , k , "\n" )

# 戻り値のない関数の例�B
def f( x )
     if x % 2 == 0 then
	print( x , "は偶数です\n" )
     else
	print( x , "は奇数です\n" )
     end
end

n = 15
f( n )

# 引数も戻り値もない関数
def max()
  x = 3
  y = 5
  if  x >= y then
    z = x
  else 
    z = y
  end
  puts( "#{z} is the maximum of #{x} and #{y}" )
end

max()

# 配列を引数として受け取る関数�@
def average( a ) 
  s=0.0
  a.each{|x|
	 s += x 
  }
  return s/a.length
end

x = [1,2,3,4,5,6,7,8,9,10]
print( "#{average( x )} is the average of: "); p( x )

# 配列を引数として受け取る関数�A
def average( a ) 
  s=0.0
  a.each{|x|
	 s += x 
  }
  return s/a.length
end

def var( a ) 
   ave = average( a )
   s = 0.0
   a.each{ |x|
	s += ( x - ave ) * ( x - ave )
   }  
   return s /(a.length-1) 
end

x = [1,2,3,4,5,6,7,8,9,10]
print( "#{average( x )} is the average of: "); p( x )
print( "#{var( x )} is the variance of: "); p( x )

# 配列を引数として受け取る関数�B
def inner_product( a , b )
  s = 0
  a.length.times{ |i|
	s += a[ i ] * b[ i ]
  }
  return s
end

x = [1,2,3,4,5]
y= [6,7,8,9,10]
print( inner_product( x , y ) , "\n" )