A block represents one or more paths of execution as a single unit. It is one of the fundamental grammatical structures of the Rant language.


A block is written as a set of curly braces containing one or more sections of code separated by vertical pipes (|). Here are a few examples:

{}              # Empty block (1 implicit element which does nothing)
{ A }           # Block with 1 element (a "linear" block)
{ A | B }       # Block with 2 elements
{ A | B | C }   # Block with 3 elements

Use cases

Blocks serve several purposes in Rant, ranging from simple branch selection to collection generation and even loops. They can contain any valid Rant code—even other blocks.

Item selection

By default, a block randomly selects one of its elements and runs the code inside.

# Randomly prints "Heads" or "Tails" with uniform probability

The selection strategy can be customized if needed using a selector.

Collection generation

Blocks can be used to combine collections with conditional, repeating, or probabilistic elements.

# Evaluates to (A; B; C) or (A; D; E)
{ (A;) { (B; C) | (D; E) } }
# Evaluates to (1; 2; 3; 4; 5; 6; 7; 8; 9; 10)
[rep: 10] { ([step]) }

Important to note:

Blocks used for function bodies and dynamic accessor keys are slightly different:

  1. They are strictly linear: they can only contain a single element. Adding multiple elements will cause a compiler error.
  2. They never consume attributes: Attributes must be explicitly consumed by adding an inner block.


A selector can "entangle" several blocks to coordinate their behavior.

# Create a selector and store it in <sync>
[mksel:one > %sync]
# Both blocks use the `sync` selector, so they're entangled
[sel:<sync>]{Dogs|Cats} say \"[sel:<sync>]{woof|meow}!\"

Possible outputs:
- Dogs say "woof!"
- Cats say "meow!"

Variable scope

Blocks act as scopes for local variables. Any variables created inside of a block are destroyed immediately after the block resolves.

    <%pi = 3.14>    # Create a variable called `pi`
    <pi>            # Prints 3.14 to the output
}                   # `pi` goes out of scope here
<pi>                # Error!