[Do not merge yet] Swift Package Manager support

[ole]

Requires Swift 3.1 so we shouldn't merge this yet.

[ole]

The library builds on macOS 10.12 with this command, using a recent Swift snapshot (I used DEVELOPMENT-SNAPSHOT-2017-01-20-a for testing):

swift build -Xswiftc "-target" -Xswiftc "x86_64-apple-macosx10.12"

When I compile the tests with:

swift test -Xswiftc "-target" -Xswiftc "x86_64-apple-macosx10.12"

I get these build errors:

Compile Swift Module 'AmpereTests' (14 sources)
/Users/elo/code/Writing/2016-07 Ampere/Tests/AmpereTests/UnitAreaTests.swift:17:27: error: binary operator '/' cannot be applied to operands of type 'Measurement<UnitArea>' and 'Measurement<UnitLength>'
        let height = area / width
                     ~~~~ ^ ~~~~~
/Users/elo/code/Writing/2016-07 Ampere/Tests/AmpereTests/UnitAreaTests.swift:17:27: note: expected an argument list of type '(Measurement<UnitType>, Measurement<UnitType>)'
        let height = area / width
                          ^
/Users/elo/code/Writing/2016-07 Ampere/Tests/AmpereTests/UnitAreaTests.swift:33:27: error: binary operator '/' cannot be applied to operands of type 'Measurement<UnitArea>' and 'Measurement<UnitLength>'
        let height = area / width
                     ~~~~ ^ ~~~~~
/Users/elo/code/Writing/2016-07 Ampere/Tests/AmpereTests/UnitAreaTests.swift:33:27: note: expected an argument list of type '(Measurement<UnitType>, Measurement<UnitType>)'
        let height = area / width
                          ^
<unknown>:0: error: build had 1 command failures
error: exit(1): /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2017-01-20-a.xctoolchain/usr/bin/swift-build-tool -f /Users/elo/code/Writing/2016-07\ Ampere/.build/debug.yaml test

I have no idea why. The same tests compile and run fine in Xcode (in an iOS target, but I think that shouldn't make a difference).

[ole]

The tests now compile on Linux but I'm seeing some test failures. Not sure why. I'm using the Docker Swift image (https://hub.docker.com/_/swift/).

$ swift --version
Swift version 3.0.2 (swift-3.0.2-RELEASE)
Target: x86_64-unknown-linux-gnu
$ swift test
Compile Swift Module 'AmpereTests' (14 sources)
Linking ./.build/debug/AmperePackageTests.xctest
Test Suite 'All tests' started at 18:57:59.466
Test Suite 'debug.xctest' started at 18:57:59.467
Test Suite 'DivisionByItselfTests' started at 18:57:59.467
Test Case 'DivisionByItselfTests.testDivisionByItselfWithTheSameUnit' started at 18:57:59.468
Test Case 'DivisionByItselfTests.testDivisionByItselfWithTheSameUnit' passed (0.0 seconds).
Test Case 'DivisionByItselfTests.testDivisionByItselfWithDifferentUnits' started at 18:57:59.468
Test Case 'DivisionByItselfTests.testDivisionByItselfWithDifferentUnits' passed (0.0 seconds).
Test Suite 'DivisionByItselfTests' passed at 18:57:59.468
	 Executed 2 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
Test Suite 'UnitAreaTests' started at 18:57:59.468
Test Case 'UnitAreaTests.testMultiplicationWithDefaultUnits' started at 18:57:59.468
/tmp/Ampere/Tests/AmpereTests/UnitAreaTests.swift:12: error: UnitAreaTests.testMultiplicationWithDefaultUnits : XCTAssertTrue failed - "m²" is not the same unit as "m²"
Test Case 'UnitAreaTests.testMultiplicationWithDefaultUnits' failed (0.0 seconds).
Test Case 'UnitAreaTests.testDivisionWithDefaultUnits' started at 18:57:59.469
/tmp/Ampere/Tests/AmpereTests/UnitAreaTests.swift:20: error: UnitAreaTests.testDivisionWithDefaultUnits : XCTAssertTrue failed - "m" is not the same unit as "m"
Test Case 'UnitAreaTests.testDivisionWithDefaultUnits' failed (0.0 seconds).
Test Case 'UnitAreaTests.testMultiplicationWithNonDefaultUnits' started at 18:57:59.469
/tmp/Ampere/Tests/AmpereTests/UnitAreaTests.swift:28: error: UnitAreaTests.testMultiplicationWithNonDefaultUnits : XCTAssertTrue failed - "m²" is not the same unit as "m²"
Test Case 'UnitAreaTests.testMultiplicationWithNonDefaultUnits' failed (0.0 seconds).
Test Case 'UnitAreaTests.testDivisionWithNonDefaultUnits' started at 18:57:59.469
Test Case 'UnitAreaTests.testDivisionWithNonDefaultUnits' passed (0.0 seconds).
Test Suite 'UnitAreaTests' failed at 18:57:59.470
	 Executed 4 tests, with 3 failures (0 unexpected) in 0.001 (0.001) seconds
Test Suite 'UnitElectricChargeTests' started at 18:57:59.470
Test Case 'UnitElectricChargeTests.testWithBaseUnits' started at 18:57:59.470
Test Case 'UnitElectricChargeTests.testWithBaseUnits' passed (0.0 seconds).
Test Case 'UnitElectricChargeTests.testWithNonBaseUnits' started at 18:57:59.470
Test Case 'UnitElectricChargeTests.testWithNonBaseUnits' passed (0.0 seconds).
Test Suite 'UnitElectricChargeTests' passed at 18:57:59.470
	 Executed 2 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
Test Suite 'UnitElectricPotentialDifferenceTests' started at 18:57:59.471
Test Case 'UnitElectricPotentialDifferenceTests.testWithBaseUnits' started at 18:57:59.471
Test Case 'UnitElectricPotentialDifferenceTests.testWithBaseUnits' passed (0.0 seconds).
Test Case 'UnitElectricPotentialDifferenceTests.testWithNonBaseUnits' started at 18:57:59.471
Test Case 'UnitElectricPotentialDifferenceTests.testWithNonBaseUnits' passed (0.0 seconds).
Test Suite 'UnitElectricPotentialDifferenceTests' passed at 18:57:59.471
	 Executed 2 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
Test Suite 'UnitEnergyTests' started at 18:57:59.471
Test Case 'UnitEnergyTests.testWithBaseUnits' started at 18:57:59.472
Test Case 'UnitEnergyTests.testWithBaseUnits' passed (0.0 seconds).
Test Case 'UnitEnergyTests.testWithNonBaseUnits' started at 18:57:59.472
Test Case 'UnitEnergyTests.testWithNonBaseUnits' passed (0.0 seconds).
Test Suite 'UnitEnergyTests' passed at 18:57:59.472
	 Executed 2 tests, with 0 failures (0 unexpected) in 0.001 (0.001) seconds
Test Suite 'UnitForceTests' started at 18:57:59.473
Test Case 'UnitForceTests.testBaseUnitIsNewtons' started at 18:57:59.473
Test Case 'UnitForceTests.testBaseUnitIsNewtons' passed (0.0 seconds).
Test Case 'UnitForceTests.testUnitsWithSameSymbolAndConverterAreEqual' started at 18:57:59.473
/tmp/Ampere/Tests/AmpereTests/UnitForceTests.swift:15: error: UnitForceTests.testUnitsWithSameSymbolAndConverterAreEqual : XCTAssertEqual failed: ("<UnitForce: 0x0000000000faf140>") is not equal to ("<UnitForce: 0x0000000000fac750>") -
Test Case 'UnitForceTests.testUnitsWithSameSymbolAndConverterAreEqual' failed (0.0 seconds).
Test Case 'UnitForceTests.testKiloNewtons' started at 18:57:59.473
/tmp/Ampere/Tests/AmpereTests/UnitForceTests.swift:21: error: UnitForceTests.testKiloNewtons : XCTAssertEqual failed: ("10.0 kN") is not equal to ("10000.0 N") -
Test Case 'UnitForceTests.testKiloNewtons' failed (0.0 seconds).
Test Case 'UnitForceTests.testKiloponds' started at 18:57:59.474
/tmp/Ampere/Tests/AmpereTests/UnitForceTests.swift:27: error: UnitForceTests.testKiloponds : XCTAssertEqual failed: ("1000.0 kp") is not equal to ("9806.65 N") -
Test Case 'UnitForceTests.testKiloponds' failed (0.0 seconds).
Test Case 'UnitForceTests.testWithBaseUnits' started at 18:57:59.474
Test Case 'UnitForceTests.testWithBaseUnits' passed (0.0 seconds).
Test Case 'UnitForceTests.testWithNonBaseUnits' started at 18:57:59.474
Test Case 'UnitForceTests.testWithNonBaseUnits' passed (0.0 seconds).
Test Suite 'UnitForceTests' failed at 18:57:59.474
	 Executed 6 tests, with 3 failures (0 unexpected) in 0.001 (0.001) seconds
Test Suite 'UnitLengthTests' started at 18:57:59.474
Test Case 'UnitLengthTests.testMultiplicationInMetersPerSecond' started at 18:57:59.474
Test Case 'UnitLengthTests.testMultiplicationInMetersPerSecond' passed (0.0 seconds).
Test Case 'UnitLengthTests.testMultiplicationInKilometersPerHour' started at 18:57:59.474
/tmp/Ampere/Tests/AmpereTests/UnitLengthTests.swift:20: error: UnitLengthTests.testMultiplicationInKilometersPerHour : XCTAssertEqualWithAccuracy failed: ("99000.0792") is not equal to ("99000.0") +/- ("0.001") - "99000.0792 m" is not equal to "99.0 km"
Test Case 'UnitLengthTests.testMultiplicationInKilometersPerHour' failed (0.0 seconds).
Test Case 'UnitLengthTests.testMultiplicationInMilesPerHour' started at 18:57:59.475
/tmp/Ampere/Tests/AmpereTests/UnitLengthTests.swift:28: error: UnitLengthTests.testMultiplicationInMilesPerHour : XCTAssertEqualWithAccuracy failed: ("563270.4") is not equal to ("563269.0") +/- ("0.001") - "563270.4 m" is not equal to "350.0 mi"
Test Case 'UnitLengthTests.testMultiplicationInMilesPerHour' failed (0.0 seconds).
Test Case 'UnitLengthTests.testMultiplicationInKnots' started at 18:57:59.475
/tmp/Ampere/Tests/AmpereTests/UnitLengthTests.swift:36: error: UnitLengthTests.testMultiplicationInKnots : XCTAssertEqualWithAccuracy failed: ("85191.9264") is not equal to ("85192.0") +/- ("0.001") - "85191.9264 m" is not equal to "46.0 NM"
Test Case 'UnitLengthTests.testMultiplicationInKnots' failed (0.0 seconds).
Test Case 'UnitLengthTests.testDivisionByDurationInMetersPerSecond' started at 18:57:59.475
Test Case 'UnitLengthTests.testDivisionByDurationInMetersPerSecond' passed (0.0 seconds).
Test Case 'UnitLengthTests.testDivisionByDurationInKilometersPerHour' started at 18:57:59.476
Test Case 'UnitLengthTests.testDivisionByDurationInKilometersPerHour' passed (0.0 seconds).
Test Case 'UnitLengthTests.testDivisionBySpeedInMetersPerSecond' started at 18:57:59.476
Test Case 'UnitLengthTests.testDivisionBySpeedInMetersPerSecond' passed (0.0 seconds).
Test Suite 'UnitLengthTests' failed at 18:57:59.476
	 Executed 7 tests, with 3 failures (0 unexpected) in 0.002 (0.002) seconds
Test Suite 'UnitMassTests' started at 18:57:59.476
Test Case 'UnitMassTests.testWithBaseUnits' started at 18:57:59.477
Test Case 'UnitMassTests.testWithBaseUnits' passed (0.0 seconds).
Test Case 'UnitMassTests.testWithNonBaseUnits' started at 18:57:59.477
Test Case 'UnitMassTests.testWithNonBaseUnits' passed (0.0 seconds).
Test Suite 'UnitMassTests' passed at 18:57:59.477
	 Executed 2 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
Test Suite 'UnitProductTests' started at 18:57:59.477
Test Case 'UnitProductTests.testMultiplicationWithDefaultUnitMapping' started at 18:57:59.477
Test Case 'UnitProductTests.testMultiplicationWithDefaultUnitMapping' passed (0.0 seconds).
Test Case 'UnitProductTests.testMultiplicationIsCommutative' started at 18:57:59.478
Test Case 'UnitProductTests.testMultiplicationIsCommutative' passed (0.0 seconds).
Test Case 'UnitProductTests.testMultiplicationUsesPreferredUnitMapping' started at 18:57:59.478
Test Case 'UnitProductTests.testMultiplicationUsesPreferredUnitMapping' passed (0.0 seconds).
Test Case 'UnitProductTests.testMultiplicationFallsBackToDefaultUnitMapping' started at 18:57:59.478
Test Case 'UnitProductTests.testMultiplicationFallsBackToDefaultUnitMapping' passed (0.0 seconds).
Test Case 'UnitProductTests.testDivisionByFirstFactor' started at 18:57:59.478
Test Case 'UnitProductTests.testDivisionByFirstFactor' passed (0.0 seconds).
Test Case 'UnitProductTests.testDivisionBySecondFactor' started at 18:57:59.478
Test Case 'UnitProductTests.testDivisionBySecondFactor' passed (0.0 seconds).
Test Case 'UnitProductTests.testDivisionByFirstFactorUsesPreferredUnitMapping' started at 18:57:59.479
Test Case 'UnitProductTests.testDivisionByFirstFactorUsesPreferredUnitMapping' passed (0.0 seconds).
Test Case 'UnitProductTests.testDivisionBySecondFactorUsesPreferredUnitMapping' started at 18:57:59.479
Test Case 'UnitProductTests.testDivisionBySecondFactorUsesPreferredUnitMapping' passed (0.0 seconds).
Test Case 'UnitProductTests.testMultiplicationWithNonProportionalUnits' started at 18:57:59.479
Test Case 'UnitProductTests.testMultiplicationWithNonProportionalUnits' passed (0.0 seconds).
Test Case 'UnitProductTests.testDivisionByFirstFactorWithNonProportionalUnits' started at 18:57:59.479
Test Case 'UnitProductTests.testDivisionByFirstFactorWithNonProportionalUnits' passed (0.0 seconds).
Test Case 'UnitProductTests.testDivisionBySecondFactorWithNonProportionalUnits' started at 18:57:59.479
Test Case 'UnitProductTests.testDivisionBySecondFactorWithNonProportionalUnits' passed (0.0 seconds).
Test Suite 'UnitProductTests' passed at 18:57:59.480
	 Executed 11 tests, with 0 failures (0 unexpected) in 0.002 (0.002) seconds
Test Suite 'UnitSpeedTests' started at 18:57:59.480
Test Case 'UnitSpeedTests.testWithBaseUnits' started at 18:57:59.480
Test Case 'UnitSpeedTests.testWithBaseUnits' passed (0.0 seconds).
Test Case 'UnitSpeedTests.testWithNonBaseUnits' started at 18:57:59.480
Test Case 'UnitSpeedTests.testWithNonBaseUnits' passed (0.0 seconds).
Test Suite 'UnitSpeedTests' passed at 18:57:59.480
	 Executed 2 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
Test Suite 'UnitVolumeTests' started at 18:57:59.480
Test Case 'UnitVolumeTests.testWithBaseUnits' started at 18:57:59.480
Test Case 'UnitVolumeTests.testWithBaseUnits' passed (0.0 seconds).
Test Case 'UnitVolumeTests.testWithNonBaseUnits' started at 18:57:59.480
/tmp/Ampere/Tests/AmpereTests/UnitVolumeTests.swift:20: error: UnitVolumeTests.testWithNonBaseUnits : XCTAssertEqual failed: ("0.0001 m³") is not equal to ("0.001 m³") - "0.0001 m³" is not equal to "100.0 cm³"
Test Case 'UnitVolumeTests.testWithNonBaseUnits' failed (0.0 seconds).
Test Suite 'UnitVolumeTests' failed at 18:57:59.480
	 Executed 2 tests, with 1 failure (0 unexpected) in 0.0 (0.0) seconds
Test Suite 'debug.xctest' failed at 18:57:59.481
	 Executed 42 tests, with 10 failures (0 unexpected) in 0.008 (0.008) seconds
Test Suite 'All tests' failed at 18:57:59.481
	 Executed 42 tests, with 10 failures (0 unexpected) in 0.008 (0.008) seconds

[ole]

Closing in favor of #22.