ruby 簡(jiǎn)單例子
2019-10-26 19:19:04
供稿：網(wǎng)友
讓我們寫一個(gè)計(jì)算階乘的函數(shù).對(duì)于階乘的數(shù)學(xué)定義如下:
n! = 1 (當(dāng) n==0 時(shí))
= n * (n-1)! (其它情況)
在Ruby里,可以這樣來寫:
代碼如下:
def fact(n)
if n == 0
1
else
n * fact(n-1)
end
end
你可能會(huì)發(fā)現(xiàn) end 的反復(fù)出現(xiàn),正因?yàn)槿绱?Ruby被叫做"類Algol"語言.(實(shí)際上,Ruby的語法更像Eiffel).同時(shí),你也可能會(huì)發(fā)現(xiàn)這段函數(shù)缺少return語句.在這里是可以用return的,但卻不是必須的,因?yàn)橐粋€(gè)Ruby的函數(shù)會(huì)自動(dòng)返回它所最后賦值的元素.
讓我們來試試我們的階乘函數(shù).加入一行代碼會(huì)使它成為一個(gè)可工作的程序:
代碼如下:
# Program to find the factorial of a number
# Save this as fact.rb
def fact(n)
if n == 0
1
else
n * fact(n-1)
end
end
print fact(ARGV[0].to_i), "/n"
這里,ARGV是一個(gè)包含命令行參數(shù)的數(shù)組,to_i將字符串轉(zhuǎn)化為整數(shù).
% ruby fact.rb 1
1
% ruby fact.rb 5
120
當(dāng)參數(shù)為40時(shí)它可以工作嗎?它將使你的計(jì)算器產(chǎn)生溢出(overflow)...
% ruby fact.rb 40
815915283247897734345611269596115894272000000000
它確實(shí)算出來了.實(shí)際上,Ruby能處理任何你機(jī)器的內(nèi)存所允許的整數(shù).實(shí)際上400!也可以:
% ruby fact.rb 400
64034522846623895262347970319503005850702583026002959458684
44594280239716918683143627847864746326467629435057503585681
08482981628835174352289619886468029979373416541508381624264
61942352307046244325015114448670890662773914918117331955996
44070954967134529047702032243491121079759328079510154537266
72516278778900093497637657103263503315339653498683868313393
52024373788157786791506311858702618270169819740062983025308
59129834616227230455833952075961150530223608681043329725519
48526744322324386699484224042325998055516106359423769613992
31917134063858996537970147827206606320217379472010321356624
61380907794230459736069956759583609615871512991382228657857
