Ruby String Processing _ruby topics

Ruby handles strings like numbers. We enclose them in single quotes (' ... ') or double quotes ("...").

Ruby> "ABC"
"ABC"
Ruby> ' abc '
"ABC"


Single and double quotes have different effects in some cases. A string enclosed in double quotes allows characters to be drawn by a forward slash, and can be inline with #{} expressions.

Strings that are enclosed in single quotes do not interpret strings; What you see is what it is. 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 EFG"
ruby> var = "abc"
"ABC"
Ruby> "1234#{var}5678"
"1234 ABC 5678"


Ruby's string manipulation is more dexterous and intuitive than C. For example, you can concatenate a few with + and repeat a string several times:

Ruby> "foo" + "Bar"
"Foobar"
Ruby> "Foo" * 2
"Foofoo"


In C, in contrast, concatenated strings are much more clumsy because of the need for precise memory management:

Char *s = malloc (strlen (S1) +strlen (S2) +1);
strcpy (S, s1);
strcat (s, S2);
/* ... */
Free (s);


But for Ruby, we don't have to consider the space footprint of strings, which frees us from cumbersome memory management.

Here is some string processing,

Series:

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


Repeat:

Ruby> Word = Word * 2
"Foofoo"


Extract character (note: In Ruby, characters are treated as integers):

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


(The negative index is the offset from the tail of the string, not from the string header.)

Extract substring:

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 for equality:

Ruby> "foo" = "foo"
True
Ruby> "foo" = "Bar"
False


Note: In Ruby 1.0, the above results appear in uppercase letters.

OK, let's try these features. Here is a riddle of guessing words, maybe the word "riddle" is so cool in the following things;--)

# 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. Here is a dialog for the puzzle program to run.

% Ruby Guess.rb
Guess? Foobar
Sorry, you lose.
Guess? Quux
Sorry, you lose.
Guess? ^d
The word was Baz.


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