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V8 compatible floating-point to string conversion in Go

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# ftoa - V8 compatible floating-point to string conversion in Go

[![Go Reference](https://pkg.go.dev/badge/github.com/nukilabs/ftoa.svg)](https://pkg.go.dev/github.com/nukilabs/ftoa)

## Overview

FTOA is a specialized floating-point to string conversion library that implements JavaScript V8 engine's formatting behavior in Go. This library ensures consistent string representation of floating-point numbers between Go and JavaScript environments.

## Features

- 100% compatible with V8's JavaScript number formatting
- Handles all edge cases (NaN, Infinity, negative zero)
- Rounds .5 up in most cases
- Uses efficient Ryū algorithm for fast and accurate conversion
- Follows V8's scientific notation thresholds (≥1e21 or <1e-6)

## Installation

```
go get github.com/nukilabs/ftoa
```

## Usage

```go
package main

import (
    "fmt"
    "github.com/nukilabs/ftoa"
)

func main() {
    // Basic usage - equivalent to JavaScript's number.toString()
    fmt.Println(ftoa.FormatFloat(123.456, 'g', -1, 64))  // "123.456"
    
    // toFixed(2) equivalent
    fmt.Println(ftoa.FormatFloat(123.456, 'f', 2, 64))   // "123.46"
    
    // toExponential(2) equivalent
    fmt.Println(ftoa.FormatFloat(123.456, 'e', 2, 64))   // "1.23e+2"
    
    // Special values
    fmt.Println(ftoa.FormatFloat(0.0/0.0, 'g', -1, 64))  // "NaN"
    fmt.Println(ftoa.FormatFloat(1.0/0.0, 'g', -1, 64))  // "Infinity"
}
```

## JavaScript Equivalence

- `number.toString()` ↔ `ftoa.FormatFloat(value, 'g', -1, 64)`
- `number.toFixed(n)` ↔ `ftoa.FormatFloat(value, 'f', n, 64)`
- `number.toExponential(n)` ↔ `ftoa.FormatFloat(value, 'e', n, 64)`
- `number.toPrecision(n)` ↔ `ftoa.FormatFloat(value, 'g', n, 64)`

## V8 Compatibility

This library guarantees string representations identical to JavaScript's implicit string conversion (as if you were doing `"" + number` in JavaScript). Key differences from Go's standard library:

1. **Scientific notation thresholds**:
   - V8: Scientific notation for values ≥1e21 or <1e-6
   - Go: Different thresholds in standard library

2. **Rounding behavior**:
   - V8: Rounds .5 up in most cases
   - Go: Uses IEEE round-to-even by default

3. **Formatting of special values**:
   - V8: "Infinity" and "NaN" (not "Inf" or "NaN")
   - Go's standard formatting is different

## Why FTOA?

When building systems that communicate between Go backends and JavaScript frontends, consistent string representation of numbers is critical for:

- JSON serialization
- API contracts
- Testing and validation
- Data interchange

FTOA ensures that floating-point numbers are formatted consistently across language boundaries.

## License

This project is licensed under the MIT license that can be found in the LICENSE file.

## Acknowledgments

- Based on Go's standard library decimal conversion algorithms
- Uses the Ryū algorithm for efficient binary-to-decimal conversion 
- Carefully tuned to match V8's JavaScript number formatting

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