Ruby 字元串處理

Ruby將字元串像數字一樣處理.我們用單引號('...')或雙引號("...")將它們括起來.

ruby> "abc"

"abc"

ruby> 'abc'

"abc"

單引號和雙引號在某些情況下有不同的作用.一個由雙引號括起來的字元串允許字元由一個前置的斜杠引出,而且可以用#{}內嵌表達式.而

單引號括起來的字元串並不會對字元串作任何解釋;你看到的是什麼便是什麼.幾個例子:

ruby> print "a\nb\nc","\n"

a

c

nil

ruby> print 'a\nb\n',"\n"

a\nb\nc

nil

ruby> "\n"

"\n"

ruby> '\n'

"\\n"

ruby> "\001"

"\001"

ruby> '\001'

"\\001"

ruby> "abcd #{5*3} efg"

"abcd 15 efg"

ruby> var = " abc "

" abc "

ruby> "1234#{var}5678"

"1234 abc 5678"

Ruby的字元串操作比C更靈巧,更直觀.比如說,你可以用+把幾個串連起來,用*把一個串重複好幾遍:

ruby> "foo" + "bar"

"foobar"

ruby> "foo" * 2

"foofoo"

相比之下,在C里,因為需要精確的內存管理,串聯字元串要笨拙的多:

char *s = malloc(strlen(s1)+strlen(s2)+1);

strcpy(s, s1);

strcat(s, s2);

/* ... */

free(s);

但對於Ruby,我們不需要考慮字元串的空間佔用問題,這令到我們可以從煩瑣的內存管理中解脫出來.

下面是一些字元串的處理,

串聯:

ruby> word = "fo" + "o"

"foo"

重複:

ruby> word = word * 2

"foofoo" 

抽取字元(注意:在Ruby里,字元被視為整數):

ruby> word[0]

102 # 102 is ASCII code of `f' 

ruby> word[-1]

111 # 111 is ASCII code of `o' 

(負的索引指從字元串尾算起的偏移量,而不是從串頭.)

提取子串:

ruby> herb = "parsley"

"parsley"

ruby> herb[0,1]

"p"

ruby> herb[-2,2]

"ey"

ruby> herb[0..3]

"pars"

ruby> herb[-5..-2]

"rsle" 

檢查相等:

ruby> "foo" == "foo"

true

ruby> "foo" == "bar"

false 

注意:在Ruby 1.0里,以上結果以大寫字母出現.

好,讓我們來試試這些特性.下面是一個猜詞的謎題,可能"謎題"這個詞用在下面的東西上太酷了一點;-)

# save this as guess.rb

words = ['foobar', 'baz', 'quux']

secret = words[rand(3)]

print "guess? "

while guess = STDIN.gets 

guess.chop! 

if guess == secret

print "You win!\n" 

break 

else 

print "Sorry, you lose.\n" 

end 

print "guess? "

end

print "The word was ", secret, ".\n"

現在,別太擔心代碼細節了.下面是謎題程序運行的一個對話.

% ruby guess.rb

guess? foobar

Sorry, you lose.

guess? quux

Sorry, you lose.

guess? ^D

The word was baz. 

(考慮到1/3的成功率,也許我本該做得好一點.)