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rop (Runtime Operator Parser)

rop is a TypeScript/JavaScript library that can parses and evaluates expressions via tagged template literals. It supports operator overloading for custom and built-in types, enabling custom behaviors for JS operators and Python-style array slicing.

Usage examples

Before reading the Quick Tutorial, these examples below show what rop can do:

Evaluate a simple expression

o`2 + 3` // 5

// Value embedding
o`${2} + 3` // 5

Array Slicing

Python-style array slicing syntax:

Rop.INST.bind({ arr: [1, 2, 3, 4, 5] })

// Basic slicing
o`arr[1:3]` // [2, 3]

// Negative indices
o`arr[:-2]` // [1, 2, 3]

// With step
o`arr[::2]` // [1, 3, 5]

// Reverse
o`arr[::-1]` // [5, 4, 3, 2, 1]

// Multi-dimensional slicing (for custom types)
o`${tensor}[2:5, 1:5, 4:7]`

Operator overload for Array

o`${[2, 3]} + ${[4, 5]}` // [2, 3, 4, 5]

Operator overloading for Set

Rop.INST.bind({
  a: new Set([1, 2, 3]),
  b: new Set([3, 4, 5]),
})
o`a + b` // Set { 1, 2, 3, 4, 5 }

Property access and indexing

Rop.INST.bind({
  obj: { name: 'Alice' },
  arr: [1, 2, 3],
})

// access property `name` on `obj`
o`obj.name` // Alice

// index `obj` with `name`
o`obj['name']` // Alice
o`arr[1]` // 2

Operator overloading for custom type Vec2 (assume you have it implemented)

// bind identifiers `a` and `b`, so you can use them in the expression.
rop.bind({
  a: new Vec2(2, 3),
  b: new Vec2(3, 4),
})
rop.o<Vec2>`a + b` // Vec2 { x: 5, y: 7 }