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Basics.md

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Basics

Comments

Comments are available in 2 varieties. Perl-style comments begin with a # and continue to the end of the line.

123 # This is a comment.
#= Number.Integer(123)

# This is a comment.
456
#= Number.Integer(456)

# This is a comment.
789
# This is another comment.
#= Number.Integer(789)

Block comments start with #[ and end with ]#. Note that block comments cannot be nested; the first ]# will always end the comment and return to processing code.

123 #[ This is a comment. ]#
#= Number.Integer(123)

1 #[ This is a comment. ]# + 2
#= Number.Integer(3)

456 #[ This is a
       multi-line
       comment.
]#
#= Number.Integer(456)

Variables

Stone has variables, much like any other programming language. Variable names, along with function names, property names, and method names, are called identifiers.

An identifier must not start with a number. An identifier cannot contain whitespace, (non-printable) control characters, or any of these characters: :",.;#@`^\()[]{}«» Other than that, an identifier can any combination of letters, numbers, and symbols.

a := 123
a
#= Number.Integer(123)

b
#! UndefinedVariable: b

c_2 := "Hello"
if(TRUE, { c_2 })
#= Text("Hello")

Conditionals

Stone uses blocks to indicate code that might run later. This allows if to be written as a function. The then clause of an if conditional is passed as the 2nd argument. The if function takes an optional 3rd argument, which acts as the else clause.

There's also unless, which is the same as if, but with TRUE and FALSE cases reversed.

if(TRUE, { 1 })
#= Number.Integer(1)

if(FALSE, { 1 })
#= Null(Null.NULL)

unless(FALSE, { 123 })
#= Number.Integer(123)

if(2 < 1, { "2 is less than 1" }, { "2 is NOT less than 1" })
#= Text("2 is NOT less than 1")

if({ 2 < 1 }, { "2 is less than 1" }, { "2 is NOT less than 1" })
#= Text("2 is NOT less than 1")

x := 1
unless(x == 1, { "there are x things" }, { "there is 1 thing" })
#= Text("there is 1 thing")

if(TRUE)
#! ArityError: 'if' expects 2 or 3 arguments, got 1

if(TRUE, 1)
#! TypeError: 'if' argument 'then' must be a block

if(TRUE, { 1 }, 2)
#! TypeError: 'if' argument 'else' must be a block

if("Text", { "Hello" }, { "Goodbye" })
#! TypeError: 'if' condition must be a Boolean

unless({ "Text" }, { "Hello" }, { "Goodbye" })
#! TypeError: 'unless' condition must be a Boolean