Ruby string processing

Ruby processes strings like numbers. We enclose them with single quotation marks ('...') or double quotation marks.

Ruby> "abc"
"Abc"
Ruby> 'abc'
"Abc"


Single quotation marks and double quotation marks have different functions in some cases. A string enclosed by double quotation marks allows a character to be led out by a front slash, and can be embedded with a #{} expression.

Strings enclosed in single quotes do not explain the strings. What are you looking at? Several examples:

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's string operations are more agile and intuitive than C. For example, you can use + to concatenate several strings and use * to repeat a string several times:

Ruby> "foo" + "bar"
"Foobar"
Ruby> "foo" * 2
"Foofoo"


In contrast, in C, because precise memory management is required, concatenating strings is much more clumsy:

Char * s = malloc (strlen (s1) + strlen (s2) + 1 );
Strcpy (s, s1 );
Strcat (s, s2 );
/*...*/
Free (s );


But for Ruby, we do not need to consider the space occupation of strings, which frees us from the cumbersome memory management.

Below are some strings for processing,

Series:

Ruby> word = "fo" + "o"
"Foo"


Repeat:

Ruby> word = word * 2
"Foofoo"


Extract characters (Note: In Ruby, the characters are considered as integers ):

Ruby> word [0]
102 #102 is ASCII code of 'F'
Ruby> word [-1]
111 #111 is ASCII code of 'O'


(A negative index refers to the offset calculated from the end of the string, rather than from the string header .)

Extract substrings:

Ruby> herb = "parsley"
"Parsley"
Ruby> herb [0, 1]
"P"
Ruby> herb [-2, 2]
"Ey"
Ruby> herb [0 .. 3]
"Pars"
Ruby> herb [-5...-2]
"Rsle"


Check equal:

Ruby> "foo" = "foo"
True
Ruby> "foo" = "bar"
False


Note: In Ruby 1.0, the above results are displayed with uppercase letters.

Well, let's try these features. The following is a guessing puzzle. Maybe the word "Puzzle" is a little cool in the following ;-)

# 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"


Now, don't worry too much about the code details. The following is a dialogue for running the puzzle program.

% Ruby guess. rb
Guess? Foobar
Sorry, you lose.
Guess? Quux
Sorry, you lose.
Guess? ^ D
The word was baz.


(Considering the success rate of 1/3, maybe I should have done a little better .)