Formula

A formula engine implemented in Go that parses and evaluates mathematical and logical expressions.

Overview

Formula is a Go-based expression evaluation engine that parses formulas into an Abstract Syntax Tree (AST) and evaluates them. It supports various mathematical operations, logical expressions, array functions, variable access, JSON data integration, and more.

Features

• Mathematical operations
• Logical expressions
• Comparison operators
• Array functions
• Variable support
• JSON data integration

Use cases

• Building spreadsheet-like applications
• Creating rule engines or decision systems
• Implementing custom calculation engines
• Building domain-specific languages for business rules
• Data transformation pipelines
• Calculations (Finance, Science, Statistics, Engineering, Medical, Legal, etc.)

Examples

The project includes several examples demonstrating different use cases:

• One-line expressions
• Multi-line formulas
• JSON array processing
• JSON map processing
• Compound interest calculations

Sample Formula

This is a sample formula for Compound Interest Calculation:

MULTIPLY(
  VAR('P'), 
  POW(
    ADD(
      1, 
      DIVIDE(
        VAR('r'), 
        VAR('n')
      )
    ), 
    MULTIPLY(
      VAR('n'), 
      VAR('t')
    )
  )
)

The dump format of the formula above is like this:

=== AST Visualization ===
FuncCall(MULTIPLY)
    ├── FuncCall(VAR)
    │   └── Literal(P)
    └── FuncCall(POW)
        ├── FuncCall(ADD)
        │   ├── Literal(1)
        │   └── FuncCall(DIVIDE)
        │       ├── FuncCall(VAR)
        │       │   └── Literal(r)
        │       └── FuncCall(VAR)
        │           └── Literal(n)
        └── FuncCall(MULTIPLY)
            ├── FuncCall(VAR)
            │   └── Literal(n)
            └── FuncCall(VAR)
                └── Literal(t)

Getting Started

Prerequisites

• Go 1.21.1 or higher

Building

make build

Running Tests

make test

For function-specific tests with coverage:

make test-functions
make test-functions-coverage

Project Structure

• core/: Core types and AST definitions
• engine/: Formula parsing and evaluation engine
• functions/: Implementation of supported functions and operators
• examples/: Usage examples

Available Make Commands

Run make help to see all available commands:

make help

Author

• Muhammad Wildan Aldiansyah

Contributing

Contributions are welcome! Please feel free to submit an issue or pull request.

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.