#illusory0x0/ryu

Note: This file is copied from https://github.com/moonbitlang/core/tree/main/double/internal/ryu

#Overview

#Features

• Fast conversion: Optimized algorithm for converting Double values to strings
• Multiple output formats: Support for string output, logger output, and byte array output
• ECMAScript compliance: Follows ECMAScript number-to-string specification
• Comprehensive testing: Extensively tested with edge cases and boundary conditions

#API

#to_string(val : Double) -> String

test "to_string examples" {
  inspect(to_string(3.1415926), content="3.1415926")
  inspect(to_string(0.0), content="0")
  inspect(to_string(1.0 / 0.0), content="Infinity")
  inspect(to_string(-1.0 / 0.0), content="-Infinity")
  inspect(to_string(0.0 / 0.0), content="NaN")
}

#output_to_logger(val : Double, logger : &Logger) -> Unit

test "output_to_logger example" {
  let logger = StringBuilder::new(size_hint=60)
  output_to_logger(42.0, logger)
  inspect(logger.to_string(), content="42")
}

#write_to_arrayview_byte(val : Double, bv : ArrayView[Byte]) -> Int

test "write_to_arrayview_byte example" {
  let buffer : Array[Byte] = Array::make(32, b'\xff')
  let bytes_written = write_to_arrayview_byte(123.456, buffer[:])
  // buffer now contains the UTF-8 bytes of "123.456"
  inspect(bytes_written, content="7")
  let result_str = StringBuilder::new()
  for i in 0..<bytes_written {
    result_str.write_char(buffer[i].to_char())
  }
  inspect(result_str.to_string(), content="123.456")
}

#Examples

#Basic Usage

test "basic usage examples" {
  // Simple number conversion
  inspect(to_string(42.0), content="42")
  inspect(to_string(3.14159), content="3.14159")
  inspect(to_string(1.23e-10), content="1.23e-10")

  // Special values
  inspect(to_string(0.0 / 0.0), content="NaN")
  inspect(to_string(1.0 / 0.0), content="Infinity")
  inspect(to_string(-1.0 / 0.0), content="-Infinity")
}

#Scientific Notation

test "scientific notation examples" {
  inspect(to_string(1.0e-15), content="1e-15")
  inspect(to_string(1.0e+15), content="1000000000000000")
  inspect(to_string(1.23456789e+20), content="123456789000000000000")
}

#Edge Cases

test "edge cases" {
  // Very small numbers
  inspect(to_string(2.2250738585072014e-308), content="2.2250738585072014e-308")

  // Very large numbers
  inspect(to_string(1.7976931348623157e+308), content="1.7976931348623157e+308")

  // Minimum positive value
  inspect(to_string(5.0e-324), content="5e-324")
}

#Implementation Details

• Optimized conversion algorithms for different number ranges
• Proper handling of trailing zeros
• Support for subnormal numbers
• Compliance with IEEE 754 standards

#Performance

• Avoiding expensive division operations
• Using precomputed lookup tables
• Implementing optimized algorithms for different number ranges

#License

#Credits

• Original Ryu algorithm by Ulf Adams
• MoonBit implementation adapted from moonbitlang/core
• ECMAScript compliance adjustments