Boolean

Logic

Boolean → Object

Boolean values.

Example:

True
False
a && b → in?: [True, False]
  | a is-a?: Boolean
  | b is-a?: Boolean

Test whether a and b are both True. This is actually a macro which calls the short-circuiting and:.

Example:

> True && False
False
> (1 == 1) && ($a /= $b)
True

a || b → in?: [True, False]
  | a is-a?: Boolean
  | b is-a?: Boolean

Test if either a or b are True. This is actually a macro which calls the short-circuiting or:.

Example:

> True || False
True
> (1 == 1) || ($a /= $b)
True

a and: b → in?: [True, False]
  | a is-a?: Boolean
  | b is-a?: Block

A short-circuiting form of &&, only calling the right-hand side if a is True. 

a or: b → in?: [True, False]
  | a is-a?: Boolean
  | b is-a?: Block

A short-circuiting form of ||, only calling the right-hand side if a is False. 

a not → in?: [True, False]
  | a is-a?: Boolean

Negate a.

Example:

> True not
False
> False not
True
> True not not
True

Control Flow

if: test then: yes else: no → any
  | test is-a?: Boolean
  | yes is-a?: Block
  | no is-a?: Block

Basic if-then-else control flow. If test is True, yes is called, otherwise no is. The result is the result of whichever block is called.

Example:

> if: (1 == 0) then: { "Uh-oh." } else: { "We're good!" }
"We're good!"

when: test do: action → @ok
  | test is-a?: Boolean
  | action is-a?: Block

Sends call to action in-context if test is True, always returning @ok.

Example:

> a = 0
0
> b := when: (a == 1) do: { "a is 1!" print }
@ok
> b
@ok
> a = 1
1
> b
a is 1!
@ok

while: test do: action → @ok
  | test is-a?: Block
  | action is-a?: Block

Continually sends call to action in-context until test yields False.

Example:

> a = 1
1
> while: { a < 10 } do: { a = a + 1 }
@ok
> a
10

condition: branches → any
  | branches is-a?: Block

Similar to Scheme's cond, this construct takes a block pairing tests with their branch, and goes through each pairing until a test yields True, in which case it evaluates the expression that test was associated with.

If no branches yield True, @no-true-branches is raised.

NOTE: This is a macro which expands to chained if:then:else: dispatches.

Example:

> condition: { False -> "Hello!" print; True -> "Goodbye!" print }
Goodbye!
"Goodbye!"
> condition: { 1 == 1 -> 0; otherwise -> 1 }
0

otherwise → True

Alias for True for use in condition:, or anywhere else where it would look nicer.