Booleans

Booleans are implemented with messages - they are not built-in keywords like in other languages!

true:
false:

There is no if in gab. Typically, a defcase is used instead:

my_message: .defcase! {
    true: (args) => do
        # Do something with args in the truthy case
    end
    false: (args) => do
        # Do something with args in the falsey case
    end
}

some_condition .my_message args

For simple use cases, there are messages and:, or:, then: and else: defined in the core library.

# Lifted from gab's core library.

truthy_values .defmodule! {
  and: (alt[]) => alt**
  or: _ => self

  then: f => f. self
  else: _ => self
}

falsey_values .defmodule! {
  and: _ => self
  or: (alt[]) => alt**

  then: _ => self
  else: f => f. self
}

The and: and or: messages do what you expect for the most part, except they don’t short circuit. This means the value on the right is always evaluated.

true: .and 2  # 2
false: .and 2 # .false
false: .or 2  # 2
true: .or 2   # .true

The then: and else: messages do short circuit, by accepting blocks instead of values.

true: .then () => do
    # Do something in the truthy case
end
false: .else () => do
    # Do something in the falsey case
end

This is is the part of Gab that some may find to be most inconvenient. However, I find that it encourages writing smaller functions and more modular code, as nesting lots of scopes and conditionals is impossible.