Add a SexagesimalPrefix to the API?

[laeubi]

Problem: Current prefix systems (MetricPrefix with base-10, BinaryPrefix with base-1024) don't cover time units which use base-60 (sexagesimal) for minutes and hours.

Proposal: Add SexagesimalPrefix enum with MINUTE (60¹) and HOUR (60²) constants, following the same pattern as existing prefix implementations.

Benefits:

• Consistent with existing MetricPrefix and BinaryPrefix design
• Provides natural way to express time unit relationships
• Follows historical/traditional time measurement conventions

An implementation might look like this

/**
 * Provides support for sexagesimal (base-60) prefixes used in time measurement. 
 * Unlike metric (base-10) and binary (base-1024) prefixes, time units traditionally
 * use base-60 for minutes and hours. 
 * 
 * <p>
 * For example: 
 * <pre>
 * {@code import static tech.units.indriya.unit.Units.*;
 * import static javax.measure. SexagesimalPrefix.*;
 * import javax.measure.*;
 * import javax.measure. quantity.*;
 * ...
 * Unit<Time> MINUTE = MINUTE(SECOND);  // 60 seconds
 * Unit<Time> HOUR = HOUR(SECOND);      // 3600 seconds
 * }
 * </pre>
 * 
 * You could also apply <code>Unit. prefix</code>:
 * <pre>
 * {@code ...
 * Unit<Time> MINUTE = SECOND.prefix(MINUTE);
 * Unit<Time> HOUR = SECOND.prefix(HOUR);
 * }
 * </pre>
 * 
 * <p>
 * <b>Do not use ordinal() to obtain the numeric representation of SexagesimalPrefix. 
 * Use getValue() and getExponent() instead.</b>
 * </p>
 * 
 * <dl>
 * <dt><span class="strong">Implementation Requirements</span></dt>
 * <dd>This is an immutable and thread-safe enum.</dd>
 * </dl>
 * 
 * @see <a href="https://en.wikipedia.org/wiki/Sexagesimal">Wikipedia:  Sexagesimal</a>
 */
public enum SexagesimalPrefix implements Prefix {
    /** Prefix for 60 (minute). */
    MINUTE("min", 1),
    /** Prefix for 3600 (hour = 60²). */
    HOUR("h", 2);

    /**
     * The symbol of this prefix, as returned by {@link #getSymbol}. 
     *
     * @serial
     * @see #getSymbol()
     */
    private final String symbol;

    /**
     * Exponent part of the associated factor in base^exponent representation.
     */
    private final int exponent;

    /**
     * Creates a new prefix.
     *
     * @param symbol
     *          the symbol of this prefix. 
     * @param exponent
     *          part of the associated factor in base^exponent representation.
     */
    private SexagesimalPrefix(String symbol, int exponent) {
        this.symbol = symbol;
        this.exponent = exponent;
    }

    /**
     * Returns the specified unit multiplied by the factor <code>60</code> (sexagesimal prefix).
     *
     * @param <Q>
     *          type of the quantity measured by the unit.
     * @param unit
     *          any unit.
     * @return <code>unit.prefix(60)</code>.
     */
    public static <Q extends Quantity<Q>> Unit<Q> MINUTE(Unit<Q> unit) {
        return unit.prefix(MINUTE);
    }

    /**
     * Returns the specified unit multiplied by the factor <code>3600</code> (sexagesimal prefix).
     *
     * @param <Q>
     *          type of the quantity measured by the unit.
     * @param unit
     *          any unit.
     * @return <code>unit.prefix(3600)</code>.
     */
    public static <Q extends Quantity<Q>> Unit<Q> HOUR(Unit<Q> unit) {
        return unit.prefix(HOUR);
    }

    /**
     * Returns the symbol of this prefix.
     *
     * @return this prefix symbol, not {@code null}.
     */
    @Override
    public String getSymbol() {
        return symbol;
    }

    /**
     * Base part of the associated factor in {@code base^exponent} representation. 
     * For sexagesimal prefix, this is always 60.
     */
    @Override
    public Integer getValue() {
        return 60;
    }

    /**
     * Exponent part of the associated factor in {@code base^exponent} representation.
     */
    @Override
    public int getExponent() {
        return exponent;
    }

    /**
     * Returns the name of this prefix.
     *
     * @return this prefix name, not {@code null}.
     */
    @Override
    public String getName() {
        return name();
    }
}

Any thoughts?

[desruisseaux]

Aren't hour and minutes scaled units instead of prefixes? For example, "kilo" is a prefix because with "k" for kilo and "m" for metre, we form "km" for kilometre. But "min" is not a prefix: we do not combine "min" with "s" for forming "mins".

Instead, the following should work for producing minutes and hours from seconds. For example with the Seshat implementation (I did not verified with Indriya), MINUTE and HOUR are recognized as minutes and hours with the "min" and "h" symbols respectively.

Unit<Time> MINUTE = SECOND.multiply(60);
Unit<Time> HOUR = MINUTE.multiply(60);