# 変数の例

x=25
print( "xの値は ",x,"  です" )
x=30
print( "xの値は ",x,"  に変わりました" )

x=20; print( "xの値は ",x,"  です" )
x=30; print( "xの値は ",x,"  に変わりました" )

x=20; print( "xの値は ",x,"  です" ); x=30; print( "xの値は ",x," に変わりました" )


# いろいろのデータを一つの変数に

x=20;
print( "x is now ",x );
x=3.14;
print( " but x is now ",x );
x="Hi!";
print( " but now x is ",x )


# 整数型の可能性

def factorial(n) (1..n).inject{|a,b| a*b} end
factorial(10)
factorial(100)


# 進んで考えたい人のために

def factorial(n) if n<=1 then 1 else n*factorial(n-1) end end
factorial(10)

def factorial(n) r=1; (2..n).each{ |i| r*=i }; r end
factorial(10)

def factorial(n) r=1; for i in 2..n; r*=i end; r end
factorial(10)


# 暇な人向けの問題

def fct(n,f=1) if n<=1 then f else fct(n-1,n*f) end end
fct(10)

def factorial(n) (1..n).inject{|x,y| x*y} end
factorial(10)

def factorial(n) eval( [*(1..n)].join("*") ) end
factorial(10)


# 浮動小数点型 Ruby の場合

printf("%.50f\n", 1.0/3)


# 複雑な式

Math.sin(Math::PI * 0.1) + Math.exp(Math.log( Math::PI + 0.1))


# 論理式
3 == 3
3 > 2 and 4 > 3
"abc" == "abc" or "xyz" == "XYZ"


# if then else end
x=-10
if x<0 then -x else x end

x=3
y = if x==3 then 4 else 6 end
x=4
y = if x==3 then 4 else 6 end

x = 3
if x == 3 then y = 4 else y = 6 end
x = 4
if x == 3 then y = 4 else y = 6 end

# 複雑な論理式

Math::PI > 3.14 and
( Math::E > 2.7 or 3 != 2   or
Math.sin(3.4) > 0.0
)


# if then else end

x=3
y = if x==3 then 4 else 6 end
x=4
y = if x==3 then 4 else 6 end


# もっと複雑な式

y = if Math.sin(Math::PI/4) >= 0.1  and
 ( if Math::E == 2.7 then 2 else 1 end ) > 1.5
then if Math.exp(0.5) >= 0.3 then 0.3 else 0.5 end
else Math.log(23)
end