cleanup n' smart-shift fix (#78)

oscbyspro · Apr 18, 2023 · db6a3e7 · db6a3e7
1 parent d4fab1a
commit db6a3e7
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Showing 5 changed files with 31 additions and 11 deletions.
diff --git a/Sources/ANKFullWidthKit/ANKFullWidth+Division.swift b/Sources/ANKFullWidthKit/ANKFullWidth+Division.swift
@@ -162,7 +162,7 @@ extension ANKFullWidth where High == High.Magnitude {
             return  QR(qr.quotient,   Self(digit: qr.remainder))
         }
         //=--------------------------------------=
-        let dividend_ = self.minLastIndexReportingIsZeroOrMinusOne()
+        let dividend_  = self.minLastIndexReportingIsZeroOrMinusOne()
         let minLastIndexGapSize: Int = dividend_.minLastIndex &- divisor_.minLastIndex
         let shift: Int = divisor[unchecked: divisor_.minLastIndex].leadingZeroBitCount
         //=--------------------------------------=
@@ -185,7 +185,7 @@ extension ANKFullWidth where High == High.Magnitude {
                 QUOTIENT[quotientIndex] = UInt()
             }
             //=----------------------------------=
-            for quotientIndex in QUOTIENT.indices.prefix(through: minLastIndexGapSize).reversed() {
+            for quotientIndex in QUOTIENT.indices[...minLastIndexGapSize].reversed() {
                 //=------------------------------=
                 // Approximate Quotient Digit
                 //=------------------------------=

diff --git a/Sources/ANKFullWidthKit/ANKFullWidth+Shifts.swift b/Sources/ANKFullWidthKit/ANKFullWidth+Shifts.swift
@@ -47,11 +47,11 @@ extension ANKFullWidth {
     ///   - amount: `Int.min <= amount <= Int.max`
     ///
     @inlinable mutating func _bitshiftLeftSmart(by amount: Int) {
-        let amountAbsoluteValue: Int = abs(amount)
-        switch (amount >= 0, amountAbsoluteValue < Self.bitWidth) {
-        case (true,  true ): self._bitshiftLeft(by:  amountAbsoluteValue)
+        let amountAbsoluteValue = amount.magnitude  as UInt
+        switch (amount >= 0, amountAbsoluteValue <  UInt(bitPattern: Self.bitWidth)) {
+        case (true,  true ): self._bitshiftLeft(by:  Int(bitPattern: amountAbsoluteValue))
         case (true,  false): self = Self(repeating:  false)
-        case (false, true ): self._bitshiftRight(by: amountAbsoluteValue)
+        case (false, true ): self._bitshiftRight(by: Int(bitPattern: amountAbsoluteValue))
         case (false, false): self = Self(repeating:  self.isLessThanZero)
         }
     }
@@ -155,11 +155,11 @@ extension ANKFullWidth {
     ///   - amount: `Int.min <= amount <= Int.max`
     ///
     @inlinable mutating func _bitshiftRightSmart(by amount: Int) {
-        let amountAbsoluteValue: Int = abs(amount)
-        switch (amount >= 0, amountAbsoluteValue < Self.bitWidth) {
-        case (true,  true ): self._bitshiftRight(by: amountAbsoluteValue)
+        let amountAbsoluteValue = amount.magnitude  as UInt
+        switch (amount >= 0, amountAbsoluteValue <  UInt(bitPattern: Self.bitWidth)) {
+        case (true,  true ): self._bitshiftRight(by: Int(bitPattern: amountAbsoluteValue))
         case (true,  false): self = Self(repeating:  self.isLessThanZero)
-        case (false, true ): self._bitshiftLeft(by:  amountAbsoluteValue)
+        case (false, true ): self._bitshiftLeft(by:  Int(bitPattern: amountAbsoluteValue))
         case (false, false): self = Self(repeating:  false)
         }
     }

diff --git a/Sources/ANKFullWidthKit/ANKFullWidth+Text.swift b/Sources/ANKFullWidthKit/ANKFullWidth+Text.swift
@@ -221,7 +221,7 @@ extension String {
                     }
                 }
                 //=------------------------------=
-                assert(UTF8.distance(from: UTF8.startIndex, to: index) == count)
+                assert(UTF8[..<index].count == count)
                 return count
             }
         }

diff --git a/Tests/ANKFullWidthKitTests/192+Shifts.swift b/Tests/ANKFullWidthKitTests/192+Shifts.swift
@@ -109,6 +109,11 @@ final class Int192TestsOnShifts: XCTestCase {
         }
     }
 
+    func testBitshiftingByMinAmountDoesNotTrap() {
+        XCTAssertEqual(T(repeating: true) << Int.min, T(repeating: true ))
+        XCTAssertEqual(T(repeating: true) >> Int.min, T(repeating: false))
+    }
+
     func testBitshiftingByMaskingIsEquivalentToBitshiftingModuloBitWidth() {
         for _ in 0 ..< 100 {
             let x0 = UInt64.random(in: 0 ..< UInt64.max)
@@ -217,6 +222,11 @@ final class UInt192TestsOnShifts: XCTestCase {
         }
     }
 
+    func testBitshiftingByMinAmountDoesNotTrap() {
+        XCTAssertEqual(T(repeating: true) << Int.min, T(repeating: false))
+        XCTAssertEqual(T(repeating: true) >> Int.min, T(repeating: false))
+    }
+
     func testBitshiftingByMaskingIsEquivalentToBitshiftingModuloBitWidth() {
         for _ in 0 ..< 100 {
             let x0 = UInt64.random(in: 0 ..< UInt64.max)

diff --git a/Tests/ANKFullWidthKitTests/256+Shifts.swift b/Tests/ANKFullWidthKitTests/256+Shifts.swift
@@ -117,6 +117,11 @@ final class Int256TestsOnShifts: XCTestCase {
         }
     }
 
+    func testBitshiftingByMinAmountDoesNotTrap() {
+        XCTAssertEqual(T(repeating: true) << Int.min, T(repeating: true ))
+        XCTAssertEqual(T(repeating: true) >> Int.min, T(repeating: false))
+    }
+
     func testBitshiftingByMaskingIsEquivalentToBitshiftingModuloBitWidth() {
         for _ in 0 ..< 100 {
             let x0 = UInt64.random(in: 0 ..< UInt64.max)
@@ -234,6 +239,11 @@ final class UInt256TestsOnShifts: XCTestCase {
         }
     }
 
+    func testBitshiftingByMinAmountDoesNotTrap() {
+        XCTAssertEqual(T(repeating: true) << Int.min, T(repeating: false))
+        XCTAssertEqual(T(repeating: true) >> Int.min, T(repeating: false))
+    }
+
     func testBitshiftingByMaskingIsEquivalentToBitshiftingModuloBitWidth() {
         for _ in 0 ..< 100 {
             let x0 = UInt64.random(in: 0 ..< UInt64.max)