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little - language overview

Types

Little supports a set of basic types:

  • null - represents the absense of a value
  • number - a double-precision floating point number
  • boolean - either true or false
  • string - a reference to an immutable string
  • function - a little-defined function
  • closure - any function that captures surrounding values
  • array - 0-indexed array of values
  • table - a table of key-value pairs
  • native - reference to a natively defined C function
  • ptr - userdata pointer set by C api

These are grouped into Value and Object types, which are passed by value and reference respectively null, number, boolean, and string are the Value types. String is special in that they are immutable and stored in a global deduplication table, and the actual value passed around is an index into that.

Language statements

var

var a
var b = 10
var c = (a or 10) + b

Variables are declared with the var keyword. Only a single name is permitted per var statement, with an optional expression following the = assignment operator.

if

if a is 100 { ... }
elseif a is 150 { ... }
elseif b is a { ... }
else { ... }

Branching is done with the if statement, followed by an expression to evaluate and then a mandatory set of braces, containing the body to execute. ifs can be followed by any number of elseif statements, and optionally a final elsestatement,

for

var a = [ 100, 200, 300 ]
for item in array.each(a) { ... }

for loops come in only one flavour in little, requiring a single identifier to be the loop variable, and an expression that evaluates into an iterator function. It will be repeatedly called - and it's result stored in the loop variable - until it evaluates to null.

while

var a = 0
while a < 10 { a = a + 1 }

while loops continually evaluate their condition and execute their bodies.

break

while true { break }

break exits a loop early.

return

return "any expression!"

return exits the current execution frame, and returns a single value to the caller.

assignment

var a = 10
a = 20

Any identifier followed by = assignment.

Any top-level statement that doesn't match any of these is instead executed as an expression

Language expressions

Expressions consist of all literals and operators.

Literals

  • null is both a type and a literal value
  • number literals are any decimal number strings - 123, 0.5, 123.123 etc
  • boolean literals are either true or false
  • string literals are any double-quoted strings - "hello world!", "i love apples"
  • array literals are a list of values between brackets - [ 1, true, null, "banana" ]
  • table literals are key: value pairs grouped between braces - { a: 10 b: 20 c: true }
  • function literals are declared with this syntax: var my_fn = fn(a, b) { return a + b }
    • They are first-class objects, and can only be stored through assignment
    • Can be trivially passed as parameters as well
    • Parameter list is mandatory, even if empty

Operators

The mathematical operators +, -, *, and / only work on number values The comparison operators <, <=, >, >= also only work with numbers The comparison operators is and isnt work on all types The logical operators or, and and not compare values based on their truthiness, and return their last operand The index operator [expression] works on any table and array values The dot operator . is syntax sugar for indexing tables - my_table.my_index = 10

Truthiness

Any null or false values are considered falsy, anything else is logically true