SwanJS

SwanJS is an expression language that runs in any JavaScript environment.

swan = require('swan-js');              // load the library
evaluate = swan.parse( "3 * x" );       // compile an expression
context = swan.createContext({x:10});   // create an expression context
value = await evaluate(context);        // evaluate expression in context: 30

You can install SwanJS via npm:

npm install @onlabsorg/swan-js

Syntax

A Swan expression is simply a sequence of binary operations (operand operator operand operator operand ...), eventually grouped with parentheses (...), square braces [...] or curly braces {...}.

The available binary operations are:

• Arithmetic operations: x + y, x - y, x * y, x / y, x % y, x ^ y
• Comparison operations: x == y, x != y, x > y, x >= y, x < y, x <= y
• Logic operations: x & y, x | y
• Conditional and alternative operations: x ? y, x ; y, or combined x ? y ; z
• Pairing operation: x , y
• Application (function call): x y
• Function definition: x -> y
• Composition operations: g << f, f >> g
• Mapping operation: x => f
• Assignment operations: name = x, name: x
• Sub-contexting operation: x.y

The types of grouping available are:

• Parentheses to alter evaluation precedence: (expr)
• Square braces to create lists: [x1, x2, x3, ...]
• Curly braces to create namespaces: {n1:v1, n2=v2, n3:v3, ...}

The data types defined in swan are:

• Nothing, or empty tuple: ()
• Bool: TRUE, FALSE
• Numb: 123.4
• Text: "abc", 'abc', `abc`
• List: [a, b, c, ...]
• Namespace: {n1:v1, n2=v2, n3=v3, ...}
• Func: names -> expression
• Undefined: undefined(operationName, operands)
• Tuple: x1, x2, x3, ...

Besides these operations, Swan defines also some essential builtins, consisting in functions constants.

Learn more

• Swan expression language guide
• Swan standard modules
• JavaScript API
• Swan REPL

License

MIT

Related projects

• olojs is a template engine and content management system that uses swan as inline expression language