Collection

A collection is a general term used to group multiple values into a single unit. We use collections all the time in the real world―a book is a collection of pages, a train is a collection of train cars, and a wardrobe is a collection of clothes.

String

A string is a collection of characters, mostly treated as a single unit. It is used to store text values like a name, address, message, etc.

Initializing the string

There are various ways to initialize a string in Ruby. The following program demonstrates these methods:

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String1 = 'String1 in Single Quotes \' not "'
print(String1,"\n")
 
String2 = "String2 in Double Quotes \" not '"
print(String2,"\n")
 
String3 = '''String3 in Three Single Quotes: neither \' nor "'''
print(String3,"\n")
 
String4 = '''String4  Three quotes
         allow
         multi-line'''
print(String4,"\n")

There are a few new things that we need to understand in the code above. The following are the three ways of initializing a string variable:

  • Line 1: The text of String1 is enclosed in single quotes ' '. Here, we can add ” directly and ' preceded by \ as part of the text.
  • Line 4: The text of String2 is enclosed in double quotes " ". Here, we can add ' directly and ” preceded by \ as part of the text.
  • Line 7: The text of String3 and String4 is enclosed in three single quotes ''' '''. Here, we can add " directly and ' preceded by \ as part of the text.
  • The last method also makes it easy to assign multiple lines of text to a string variable, like in String4 lines 10–12. This isn’t possible in the other two methods.

Accessing the characters in a string

Ruby allows us to access individual characters inside a string through an integer index number. To do this, we enclose the index number in square brackets after the string variable name, as shown in the following program:

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String1 = "Educative"
print(String1,"\n")
 
print(String1[0],'=',String1[-9],"\n") # Displaying first element of string
print(String1[1],'=',String1[-8],"\n") # Displaying second element of string
print(String1[2],'=',String1[-7],"\n") # Displaying fourth element of string
print(String1[3],'=',String1[-6],"\n") # Displaying fifth element of string
print(String1[4],'=',String1[-5],"\n") # Displaying sixth element of string
print(String1[5],'=',String1[-4],"\n") # Displaying seventh element of string
print(String1[6],'=',String1[-3],"\n") # Displaying eighth element of string
print(String1[7],'=',String1[-2],"\n") # Displaying ninth element of string
print(String1[8],'=',String1[-1],"\n") # Displaying tenth element of string

The code above displays the individual characters of a string on separate lines, one by one. The first character is at the 0 index, and the index moves forward along the string in linear increments. Ruby also allows negative index numbers. The last character is at -1 index and moves backward along the string in linear decrements, as illustrated in the following figure:

Slice

A slice is a subset of characters from a string. We use the [i..f] syntax to specify the initial and final index of the string to access a slice. There are several ways to access a slice of a string, but we have to pass both values to it.

  • Use both values with ..., as in [i...f], to access the slice from index i to index f-1.
  • Use both values with .., as in [i..f], to access the slice from index i to index f.
  • Use two values separated by ,, as in [i, n], to access the slice of n characters starting from the index i.

The following code illustrates various ways of making slices. This code also demonstrates that it modifies an individual character within a string with the help of slices and concatenationThe joining of two strings with the help of the + operator..

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String1 = "Educative"
print("\nCharacters between 3rd and 5th index: ")
print(String1[3...5],"\n")
print("\nCharacters between 3rd and 3rd-last index: ")
print(String1[3...-3],"\n")
String1[9]='-'
print(String1,"\n")
String2 = String1 + ' Learner'
print(String2,"\n")
 
String3 = String2[0...10] + '-' + String2[11..-1]
print(String3,"\n")

In the code above:

  • In String1[3...5], we give the range ... a starting index 3 and an ending index 5. The string slice contains two characters, ca, at index 3 and 4 (stopping at index 5) because ... exclude the higher end of range.
  • In String1[3...-3], we give the range ... a starting index 3 and an ending index -3. The string slice contains three characters, cat, at index 3, 4, and 5 (stopping at index -3 or 6).
  • Two strings can be joined or concatenated using the + operator, as shown in String2.
  • We can directly modify an individual character at any index number like String1[9] = '-'. We can modify a character by using slicing and concatenation, as shown in String3. The [0...10] statement means that the slice is from the start of the string till the index number 10-1. The [11,-1] statement means the slice is from index number 11 to the end of the string. We can use String2 instead of String3 on the left-hand side of the assignment.

Practice for string manipulation

The following are a few example programs to practice using strings in Ruby. Clicking the “Show Solution” button will display a program that solves the respective problem. You can copy and paste the given solution into the code widget to make sure the output of your solution matches the given solution. There may be several ways of writing correct solutions in programming.

Print the characters backward

Write a program that displays the characters of a string backwards, line by line. The length of the string is restricted to nine characters only.

Sample input

"Educative"

Sample output

e
v
i
t
a
c
u
d
E
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# Write your code here.

Left shift the characters in a string

Write a program that shifts the characters of a string to the left and replaces the last position with a dot.

Sample input

myString = "Educative"

Sample output

ducative.
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# Write your code here.
myString = "Educative"
myString = myString[1...]+"."
print(myString,"\n")

Reverse the string

Write a program that stores the string into another string in reverse order. The length of the string is restricted to nine characters only.

Sample input

"Educative"

Sample output

evitacudE
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# Write your code here.

Palindrome test

A palindrome is a sequence of characters that reads the same backward and forward. Write a program that checks if a string is a palindrome. The length of the string is restricted to five characters only.

Sample input 1

"level"

Sample output 1

Palindrome

Sample input 2

"leve"

Sample output 2

Not Palindrome
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# Write your code here.