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numerus

Numerus #
Dart extensions for translating decimal numbers to Roman numerals and vice versa.

Negative numbers are not supported.
Functions will return null in place of generating nonsense.
Zero can be specified as an option to the RomanNumeralConfig.
"Common" Roman numeral format used in modern times (i.e. MDCLXVI) is
the default RomanNumeralConfig style. There are other styles: vinculum, apostrophus,
and a compact apostrophus that uses single Unicode characters instead
of tally marks. See the example below.

Examples #
import 'package:numerus/numerus.dart';

void main() {
/// 1) Nice and easy, default config is the "common" config.

var n = 418;
print(n.toRomanNumeralString());
// 'CDXVIII'

var str = 'CDXVIII';
print(str.isValidRomanNumeralValue());
// true
print(str.toRomanNumeralValue());
// 418

/// 2) You can specify other [RomanNumeralConfig]'s to change the style.
/// You can set the config globally, if you'd like.
RomanNumerals.romanNumeralsConfig = VinculumRomanNumeralsConfig();

/// 3) Vinculum config style
n = 3449671;
print(n.toRomanNumeralString());
// M̅M̅M̅C̅D̅X̅L̅MX̅DCLXXI

str = 'M̅M̅M̅C̅D̅X̅L̅MX̅DCLXXI';
print(str.isValidRomanNumeralValue());
// true
print(str.toRomanNumeralValue());
// 3449671

/// 4) You can specify the config inline, too.
/// 5) Apostrophus style
n = 2449671;
print(n.toRomanNumeralString(config: ApostrophusRomanNumeralsConfig()));
// CCCCIↃↃↃↃCCCCIↃↃↃↃCCCIↃↃↃIↃↃↃↃCCIↃↃIↃↃↃCIↃCCIↃↃIↃCLXXI

/// 6) ... but frankly, globally set is probably the most common use case
RomanNumerals.romanNumeralsConfig = ApostrophusRomanNumeralsConfig();

str = 'CCCCIↃↃↃↃCCCCIↃↃↃↃCCCIↃↃↃIↃↃↃↃCCIↃↃIↃↃↃCIↃCCIↃↃIↃCLXXI';
print(str.isValidRomanNumeralValue());
// true
print(str.toRomanNumeralValue());
// 2449671

/// 7) The compact Apostrophus style uses special Unicode characters
/// just for these symbols.
RomanNumerals.romanNumeralsConfig = CompactApostrophusRomanNumeralsConfig();
n = 347449;
print(n.toRomanNumeralString());
// ↈↈↈↂↇↁↀↀCCCCXLIX

// NOTE: if you see missing characters in this example, then you'll need to
// install a font that supports them.
str = 'ↈↈↈↂↇↁↀↀCCCCXLIX';
print(str.isValidRomanNumeralValue());
// true
print(str.toRomanNumeralValue());
// 347449

/// 8) You can specify a "nulla" (zero placeholder) if you want
/// to support zero easily.
RomanNumerals.romanNumeralsConfig = CommonRomanNumeralsConfig(nulla: 'N');
n = 0;
print(n.toRomanNumeralString());
// N

str = 'N';
print(str.isValidRomanNumeralValue());
// true
print(str.toRomanNumeralValue());
// 0
}

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Features and bugs #
Please file feature requests and bugs at the issue tracker.
Local development #
Set up an environment for local development #

Install Dart or Flutter
Install the coverage tool
$ dart pub global activate coverage
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Install lcov on your system.
e.g. macOS with brew:
$ brew install lcov
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Generate code coverage from tests #
$ ./bin/coverage-gen
# If you are on macOS and would like the report to immediately
# open, then run the following (not suitable for automation):
$ ./bin/coverage-gen -i
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