Decimo v0.9.0

20260323 (v0.9.0)

Decimo v0.9.0 updates the codebase to Mojo v0.26.2 and marks the "make it useful" phase. This release introduces three major additions:

First, a full-featured CLI arbitrary-precision calculator (decimo), powered by Decimo's BigDecimal. It includes a complete tokenizer, a shunting-yard parser, and an RPN evaluator with working-precision guard digits, supporting built-in mathematical functions (sqrt, cbrt, root, ln, log, log10, exp, trigonometric functions, abs), constants (pi, e), and configurable output formatting (scientific/engineering notation, digit delimiters, rounding modes, and precision control).

Second, the BigDecimal API is significantly expanded with methods aligned to Python's decimal.Decimal and the IEEE 754 specification, including as_tuple(), adjusted(), same_quantum(), scaleb(), fma(), copy_abs(), copy_negate(), copy_sign(), bit_count(), __float__(), engineering notation, and digit-group delimiters for to_string(). The ROUND_HALF_DOWN rounding mode is added, bringing the total to seven.

Third, Decimo gains Python bindings via Mojo's PythonModuleBuilder, exposing BigDecimal as a native Python extension module (_decimo.so) with a Pythonic Decimal wrapper for seamless interoperability.

⭐️ New in v0.9.0

CLI Calculator:

1. Implement an arbitrary-precision CLI calculator with tokenizer, shunting-yard parser, and RPN evaluator, supporting arithmetic expressions with parentheses and operator precedence (PR #170).
2. Add built-in functions (sqrt, cbrt, root, ln, log, log10, exp, sin, cos, tan, cot, csc, abs), constants (pi, e), and configurable output formatting (scientific/engineering notation, digit delimiter, padding, rounding mode) (PR #171).
3. Improve CLI error handling with token location tracing and ANSI-coloured diagnostic output (PR #178).
4. Use working precision (user precision + guard digits) for intermediate calculations to improve result accuracy (PR #182).

BigDecimal:

1. Add engineering notation (to_eng_string()) and digit-group delimiters (to_string_with_separators()) to to_string(), with optional line-width wrapping (PR #172).
2. Add utility methods: is_integer(), is_signed(), number_class(), logb(), normalize(), radix() (PR #173).
3. Implement as_tuple() returning (sign, digits, exponent), matching Python's Decimal.as_tuple() (PR #174).
4. Implement adjusted(), copy_abs(), copy_negate(), and copy_sign() aligned with Python's decimal API (PR #176).
5. Implement same_quantum() and add the ROUND_HALF_DOWN rounding mode, bringing the total to seven (PR #177).
6. Implement scaleb(), fma(), bit_count(), and __float__() (implements FloatableRaising) (PR #183).

Python Bindings:

1. Implement Python bindings via Mojo's PythonModuleBuilder, exposing BigDecimal as a native extension module _decimo.so with arithmetic, comparison, and string operations (PR #179).
2. Restructure python/ to a src layout with pyproject.toml for PyPI packaging (PR #180).

🦋 Changed in v0.9.0

1. Update the codebase to Mojo v0.26.2, adopting byte= slicing syntax, out parameter convention for constructors, and updated String/StringSlice APIs (PR #185).
2. Merge TOMLMojo into Decimo as the sub-package decimo.toml, removing standalone packaging (PR #181).
3. Rename exponent() to adjusted() for BigDecimal to align with Python's decimal module naming (PR #176).
4. Change default precision of BigDecimal to 28 significant digits, matching Python's decimal module default.
5. Remove deprecated free-function comparison aliases and legacy method names from BigDecimal (PR #173).
6. Align print_internal_representation() output style across BigInt, BigUInt, BigDecimal, and Decimal128 with dynamic column alignment (PR #169).

📚 Documentation and testing in v0.9.0

• Add comprehensive user manuals for the Decimo library and the CLI calculator (PR #184).
• Add info badges to the README file.