Heredoc syntax for multiline strings in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple heredoc string

What is the output of this Ruby code using heredoc syntax?

Ruby

str = <<-TEXT
Hello,
World!
TEXT
puts str

A Hello,\nWorld!\n

B Hello, World!

C Hello,\nWorld!

D Hello,World!\n

💡 Hint

Remember that heredoc preserves newlines exactly as written.

The heredoc syntax preserves the line breaks and includes a final newline. So the output includes both lines and ends with a newline.

❓ Predict Output

intermediate

Indentation behavior with <<- heredoc

What will this Ruby code print?

Ruby

str = <<-DOC
  Line one
  Line two
DOC
puts str

A Line one\n Line two\n

B Line one\nLine two\n

C owt eniL eno eniL

D Line one Line two

💡 Hint

The <<- syntax allows the end marker to be indented but does not remove indentation inside the string.

The indentation inside the heredoc content is preserved exactly, so the two lines start with two spaces each.

❓ Predict Output

advanced

Difference between <<- and <<~ in heredoc

What is the output of this Ruby code?

Ruby

str = <<~HEREDOC
    Hello
      World
  HEREDOC
puts str

A Hello\nWorld\n

B Hello\n World\n

C Hello\n World\n

D Hello\n World\n"

💡 Hint

The <<~ syntax removes the least common leading whitespace from all lines.

The <<~ removes the smallest indentation common to all lines, so the first line's 4 spaces are removed from both lines, preserving relative indentation.

🧠 Conceptual

advanced

Heredoc with variable interpolation

Given this Ruby code, what will be the output?

Ruby

name = "Alice"
str = <<-TEXT
Hello, #{name}!
Welcome.
TEXT
puts str

A Hello, #{name}!\nWelcome.\n

B Hello, \#{name}!\nWelcome.\n

C Hello, Alice! Welcome.

D Hello, Alice!\nWelcome.\n

💡 Hint

Double-quoted heredocs allow variable interpolation.

The heredoc with <<- uses double quotes by default, so #{name} is replaced with Alice.

🔧 Debug

expert

Why does this heredoc cause a syntax error?

This Ruby code raises a SyntaxError. What is the cause?

Ruby

str = <<HEREDOC
Hello
World
  HEREDOC
puts str

A The heredoc content must be indented to match the ending marker.

B The ending HEREDOC marker is indented, but << without a dash requires it to be at the start of the line.

C The heredoc content must not contain blank lines.

D The heredoc marker must be quoted to avoid errors.

💡 Hint

Check the position of the ending marker when using << without a dash.

When using <