Description

This PR adds a comprehensive pressure unit conversion implementation to the conversions module, supporting 25 different pressure units across multiple measurement systems.

The implementation provides a flexible API that accepts both type-safe enums and convenient string identifiers, making it suitable for various use cases from scientific computing to user-facing applications.

Changes

• Added src/conversions/pressure.rs with conversion support for 25 pressure units
• Updated src/conversions/mod.rs to include the new module and exports
• Comprehensive test suite with all edge cases covered

Supported Pressure Units

SI Units (Pascal-based)

• Pa, kPa, MPa, GPa, hPa

Atmosphere Units

• atm (standard atmosphere)
• at (technical atmosphere)
• ata (total atmosphere)

Torr Units

• Torr, mTorr

Bar Units

• bar, mbar

Imperial Units

• psi, ksi, ozf/in²

Other Metric Units

• Ba (barad), pz (pièze)

Manometric Units

• mmHg, cmHg, inHg (mercury column)
• mmH₂O, cmH₂O, inH₂O (water column)
• msw (meters seawater), fsw (feet seawater)

Features

Flexible API

The convert_pressure() function accepts both enums and strings:

// Using type-safe enums
let result = convert_pressure(100.0, PressureUnit::Psi, PressureUnit::Kilopascal)?;

// Using convenient strings
let result = convert_pressure(100.0, "psi", "kpa")?;

// Mixed usage
let result = convert_pressure(100.0, PressureUnit::Psi, "kpa")?;

Accurate Conversions

• All conversions use Pascal as the base unit for consistency
• Conversion factors based on authoritative sources
• 1 atm = 760 Torr (exact)
• 1 atm = 101,325 Pa (exact)

Comprehensive Testing

Single test function covering:

• String-based conversions (convenient for user input)
• Enum-based conversions (type-safe, compile-time checked)
• Mixed enum/string conversions
• All 25 pressure units
• Invalid input error handling
• Round-trip conversion accuracy
• Edge cases and special relationships (e.g., hPa = mbar)

Testing

All tests pass:

cargo test pressure

Implementation Details

• Uses a trait-based approach (IntoPressureUnit) to accept both enums and strings
• All conversions go through Pascal as the intermediate unit
• Case-insensitive string parsing for user convenience
• Detailed error messages listing all supported units

References

• Units of Pressure

Checklist

• Code follows the repository's style guidelines
• All tests pass
• Added comprehensive test coverage
• Updated mod.rs with new module
• Added documentation comments
• No clippy warnings
• Formatted with cargo fmt
• Supports 25 different pressure units
• Flexible API accepting both enums and strings