Expressive Basics

Good Rugo code reads almost like prose. The language gives you several tools to keep things clean and expressive — use them.

String Interpolation Everywhere

Double-quoted strings support #{} interpolation. Prefer it over concatenation — it's more readable and handles type conversion automatically.

name = "Rugo"
version = 1
puts "Welcome to #{name} v#{version}!"
puts "#{2 + 2} is the answer to 2 + 2"

Welcome to Rugo v1!
4 is the answer to 2 + 2

Any expression works inside #{} — arithmetic, function calls, variable access. The language calls __to_s() on the result, so you never need manual conversion for display purposes.

Drop the Parentheses

Rugo's preprocessor rewrites paren-free calls for you. When clarity isn't sacrificed, drop the parens — it's the Rugo way.

# Parentheses are optional for function calls
puts "hello, world"

def greet(name)
  puts "Hello, #{name}!"
end

greet "developer"

hello, world
Hello, developer!

Use parentheses when nesting calls or when the expression is complex. Drop them when the intent is obvious. puts "hello" reads better than puts("hello") — that's the whole point.

Constants Are Uppercase

Any identifier starting with an uppercase letter is a constant — it can only be assigned once. Use them for configuration values, magic numbers, and anything that shouldn't change.

PI = 3.14159
MAX_RETRIES = 3
AppName = "MyTool"

puts "#{AppName} uses PI=#{PI}, max retries: #{MAX_RETRIES}"

MyTool uses PI=3.14159, max retries: 3

Constants work inside functions too. Hash bindings are constant (you can't reassign the variable) but the hash contents can still be mutated — just like a const object in JavaScript.

Compound Assignment

Use +=, -=, *=, /=, and %= to modify variables in place. They work with numbers and strings alike.

score = 0
score += 10
score += 25
score -= 5
puts "Final score: #{score}"

msg = "Hello"
msg += ", World!"
puts msg

Final score: 30
Hello, World!

Raw Strings for Literal Content

Single-quoted strings are raw — no escape processing, no interpolation. Reach for them when you need literal backslashes or want to preserve content exactly.

path = 'C:\Users\name\Documents'
puts path

pattern = 'hello\nworld'
puts pattern

name = "Rugo"
puts 'no #{interpolation} here'

C:\Users\name\Documents
hello\nworld
no #{interpolation} here

Use double quotes when you need interpolation or escapes. Use single quotes when you need the text exactly as written — regex patterns, Windows paths, template strings.

Heredocs for Multiline Text

When you need multiple lines, heredocs keep your code clean. The squiggly form (<<~) strips common leading whitespace so your strings stay indented with your code.

name = "World"
greeting = <<~TEXT
  Hello, #{name}!
  Welcome to Rugo.
TEXT
puts greeting

Hello, World!
Welcome to Rugo.

There are four heredoc flavors:

Reach for <<~DELIM most of the time — it gives you both interpolation and clean indentation.