Conditions compiler

npm install lico

Lisp-like expressions/conditions compiler. General use-case is compile expressions from generated AST.

Usage

Lico uses lisp-like syntax for defining expressions.

import lico from 'lico';

const users = [
    {name: 'Foo', active: true},
    {name: 'bar', active: false}
];

// get "active" field from document and compare with "true"
// lico will always return a function that should be called for getting result
let active = lico(['eq', ['get', ['active']], ['ret', true]]); 

console.log(users.filter(active)); // [{name: 'Foo', active: true}]

Operations

lico uses polish notation, where first (0) element in array is a operation, rest of them is an arguments.

For example: + 1 2 will be 3. In lico it will be ['add', ['ret', 1], ['ret', 2]], where add operation is sum all their arguments, ret just return first argument.

###ret

In lico you can't just return a constant, you should write ['ret', myvar] instead, where myvar is any variable, constant or something else.

Examples:

lico(['ret', true])(); // return "true"
lico(['ret', 10])(); // return 10
lico(['ret', ['ret', true]])(); // return array ['ret', true], because it not compiles their args

###get

For getting a property from object you should use get operation. Syntax is similar to oq.

Examples:

let dog = {name: 'Lambda', age: 4};

lico(['get', ['name']])(dog); // return "Lambda"

###eq

Check for arguments is equal.

Examples:

lico(['eq', ['ret', true], ['ret', true]])(); // true
lico(['eq', ['ret', true], ['ret', false]])(); // false
lico(['eq', ['ret', true], ['ret', 1]])(); // true, because it is not strict equality

###ne

Check for arguments is not equal.

Examples:

lico(['ne', ['ret', true], ['ret', true]])(); // false
lico(['ne', ['ret', true], ['ret', false]])(); // true
lico(['ne', ['ret', false], ['ret', 0]])(); // true, because it is not strict equality

###lt

Check for first argument is less than second argument.

Examples:

lico(['lt', ['ret', 1], ['ret', 2]])(); // true

###gt

Check for first argument is greater than second argument.

Examples:

lico(['gt', ['ret', 1], ['ret', 2]])(); // false

###le

Check for first argument is less than second argument or equal.

Examples:

lico(['le', ['ret', 1], ['ret', 2]])(); // true
lico(['le', ['ret', 2], ['ret', 2]])(); // true

###ge

Check for first argument is greater than second argument or equal.

Examples:

lico(['ge', ['ret', 1], ['ret', 2]])(); // false
lico(['ge', ['ret', 2], ['ret', 2]])(); // true

###neg

Inverts a value of number.

Examples:

lico(['neg', ['ret', 1]])(); // -1

###or

Logical "OR".

Examples:

lico(['or', ['ret', 1], ['ret', 2]])(); // 1
lico(['or', ['ret', false], ['ret', 2]])(); // 2

###and

Logical "AND".

Examples:

lico(['and', ['ret', 1], ['ret', 2]])(); // 2
lico(['and', ['ret', false], ['ret', 2]])(); // false

###add

Sum of two arguments.

Examples:

lico(['add', ['ret', 1], ['ret', 2]])(); // 3

###sub

Subtracts second argument from first.

Examples:

lico(['sub', ['ret', 3], ['ret', 2]])(); // 1

###mul

Multiply arguments.

Examples:

lico(['mul', ['ret', 3], ['ret', 2]])(); // 6

###div

Divides first argument by second.

Examples:

lico(['div', ['ret', 6], ['ret', 2]])(); // 3
lico(['div', ['ret', 3], ['ret', 2]])(); // 1.5

###pow

Math.pow.

Examples:

lico(['pow', ['ret', 2], ['ret', 3]])(); // 8

Extending

You can create your own operators. Just add it to lico.operators dict.

Example:

import lico from 'lico';

lico.operators.myadd = (a, b) => {
    let ca = lico(a); // compile first argument
    let cb = lico(b); // compile second argument
    
    // you always must return a function and passing "obj" parameter to compiled arguments
    // because they can depend on it
    return (obj) => ca(obj) + cb(obj);
}

let obj = {a: 2};
lico(['myadd', ['ret', 1], ['get', ['a']]])(obj); // 3