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Chapter 03

3.1 Numbers

As any programming language, Fancy has number literal syntax built in.

3.1.1 Integers (Fixnums)

There are multiple ways to write a Fixnum (Integer value). Here's a list of possible ways to write a Fixnum:

  • 1, 123, 1_000_000, 999_888_777 etc. Underscores are ignored and used purely to be easier to read (especially large numbers)
  • Binary literals: 0b10101, 0B01010101111
  • Hexadecimal literals: 0xff, 0xAB, 0XAF
  • Octal literals: 0o77, 0O13

3.1.2 Floats

Floats only allow one way of writing them: 10.9997, 0.123, 1.0

Note: Both Fixnums and Floats can be prefixed with a - for negative numbers.

3.2 Strings

Strings are what you expect them to be.


"Hello, World"
"Hello,\n World"

This is a multi-line String
The newlines become part of the String and start and end with a triple quote,
just as in Python. They're most commonly used for docstrings, which we'll talk about
later (also copied from Python).

Fancy also has support for Ruby-like string interpolation:

"This is a String with a value interpolated: 3 ** 3 = #{3 ** 3}"
"Hello, #{name}, I'm #{age} years old."

3.3 Symbols

Symbols are unique identifiers. They're equivalent to Ruby's Symbols.



3.4 Tuples

In contrast to Ruby and like Python, Fancy has built-in literal syntax for Tuples. Tuples are constant-sized containers with index-based access to members.


(1, 2) # Tuple with values 1 and 2
(1, 2, "foo")
('foo, 'bar, "baz!")
(1, (2, 3), (4, (5, 6, 7))) # nested Tuples

# Accessing elements:
(1, 2, 3) at: 2 # => 3
(1, 2, 3)[0]    # => 1

3.5 Arrays

One of the most used data structure are arrays. In Fancy there's the Array class which provides index-based constant time access to dynamically resizable (growing) polymorphic containers. Let's have a look at some Array examples:

# An Array containing 5 integers (Fixnums)

# An Array of 2 numbers, 1 String and another Array
[1, 2, "An Array!", [4,5, "Yes, indeed!"]]

Arrays work the same way as they do, for example, in Ruby. In Fact, they're sharing the same Class as their Ruby equivalents. Anytime you're using a Fancy Array, you're also using a Ruby Array inside Rubinius. There is no wrapper in between. This is true not only for Arrays, but for all built-in types and classes where there is a Ruby equivalent available.

3.6 Hashes (Dictionaries, Hashmaps)

Hashes are unordered collections of key-value pairs with fast access through keys. They can nest arbitrarily, just as Arrays.


<['name => "Fancy", 'type => "Programming Language", 'created => 2010]>

You can of course use any other type besides Symbols as keys and values.

3.7 Blocks (BlockEnvironment, Closures)

One of the most heavily used literal values in Fancy are Blocks. They're used to implement nearly all control structures (like traditional if, else, while etc constructs) and are proper closures with interesting return semantics.

We've seen Blocks in Chapter 1 before, but for completeness, here's a list of some literal Blocks:

{ "A Block with no argument" println }
|x| { "A Block with one argument, value: #{x}" println }
|x y| { "A Block with two arguments, values: #{x} and #{y}" println }

# Seperating arguments with comma is optional, thus this is valid as well:
|x, y| { "The sum is: #{x + y}" println }

There's also Partial Blocks which can be used for Blocks only taking one argument:

@{ + 1 } # is the same as: |x| { x + 1 }
# e.g.:
[1,2,3,4] map: @{+ 1} # => [2,3,4,5]

To call a Block, you send it the call or call: message and pass the arguments in as an Array:

block = |x, y| { x + y println }
block call: [2, 3] # will print 5

3.8 Regular Expressions

Fancy, as Ruby or Perl, has Regular Expressions built-in to the language. In fact, it uses the same implementation that Ruby uses on top of Rubinius, including the same literal syntax:

/^Hello, (.*)!$/

3.9 Ranges

Fancy also has Ranges, like Ruby:

(x .. x ** x)

Chapter 4 will deal with one of Fancy's central features, namely Blocks, some more.

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