斯威夫特矩阵总和 [英] Swift matrix sum

问题描述

我正在尝试开发一个函数，如果两个矩阵等于相同维，它们可以求和，但是尝试时出现错误"EXC_BAD_INSTRUCTION".

这是我的游乐场:

import Foundation

enum RisedError: ErrorType {
    case DimensionNotEquals
    case Obvious(String)
}

func ==(lhs: Matrix, rhs: Matrix) -> Bool {
    return (lhs.rows) == (rhs.rows) && (lhs.columns) == (rhs.columns)
}

protocol Operation {
    mutating func sumWith(matrixB: Matrix) throws -> Matrix
}

struct Matrix {
    let rows: Int, columns: Int
    var grid: [Double]
    init(rows: Int, columns: Int) {
        self.rows = rows
        self.columns = columns
        grid = Array(count: rows * columns, repeatedValue: 0.0)
    }
    func indexIsValidForRow(row: Int, column: Int) -> Bool {
        return row >= 0 && row < rows && column >= 0 && column < columns
    }
    subscript(row: Int, column: Int) -> Double {
        get {
            assert(indexIsValidForRow(row, column: column), "Index out of range")
            return grid[(row * columns) + column]
        }
        set {
            assert(indexIsValidForRow(row, column: column), "Index out of range")
            grid[(row * columns) + column] = newValue
        }
    }
}

var matrixA = Matrix(rows: 2, columns: 2)
matrixA[0,0] = 1.0
matrixA[0,1] = 2.0
matrixA[1,0] = 3.0
matrixA[1,1] = 4.0
var matrixB = Matrix(rows: 2, columns: 2)
matrixB[0,0] = 5.0
matrixB[0,1] = 6.0
matrixB[1,0] = 7.0
matrixB[1,1] = 8.0

print(matrixA)
print(matrixB)

extension Matrix: Operation {

    mutating func sumWith(matrixB: Matrix) throws -> Matrix {

        guard self == matrixB else { throw RisedError.DimensionNotEquals }

        for row in 0...self.rows {
            for column in 0...self.columns {
                self[row, column] = matrixB[row, column] + self[row, column]
            }
        }
        return self
    }
}

do {
    try matrixA.sumWith(matrixB)
} catch RisedError.DimensionNotEquals {
    print("The two matrix's dimensions aren't equals")
} catch {
    print("Something very bad happens")
}

这是错误日志:

解决方案

问题是您正在使用 @MartinR在上面的评论 –将矩阵的相等性定义为仅基于相同的尺寸似乎是不合逻辑的.请记住，平等意味着可替代性(即，如果a == b，a和b可互换).

我会考虑更改您的==以同时检查维度和值，然后在您的sumWith方法中实现自己的维度检查(或创建一个新的比较维度的方法). /p>

I'm trying to develop a func which allows to sum two matrix if they are equals to the same dimension, but I get an error "EXC_BAD_INSTRUCTION" on the try.

Here is my Playground:

import Foundation

enum RisedError: ErrorType {
    case DimensionNotEquals
    case Obvious(String)
}

func ==(lhs: Matrix, rhs: Matrix) -> Bool {
    return (lhs.rows) == (rhs.rows) && (lhs.columns) == (rhs.columns)
}

protocol Operation {
    mutating func sumWith(matrixB: Matrix) throws -> Matrix
}

struct Matrix {
    let rows: Int, columns: Int
    var grid: [Double]
    init(rows: Int, columns: Int) {
        self.rows = rows
        self.columns = columns
        grid = Array(count: rows * columns, repeatedValue: 0.0)
    }
    func indexIsValidForRow(row: Int, column: Int) -> Bool {
        return row >= 0 && row < rows && column >= 0 && column < columns
    }
    subscript(row: Int, column: Int) -> Double {
        get {
            assert(indexIsValidForRow(row, column: column), "Index out of range")
            return grid[(row * columns) + column]
        }
        set {
            assert(indexIsValidForRow(row, column: column), "Index out of range")
            grid[(row * columns) + column] = newValue
        }
    }
}

var matrixA = Matrix(rows: 2, columns: 2)
matrixA[0,0] = 1.0
matrixA[0,1] = 2.0
matrixA[1,0] = 3.0
matrixA[1,1] = 4.0
var matrixB = Matrix(rows: 2, columns: 2)
matrixB[0,0] = 5.0
matrixB[0,1] = 6.0
matrixB[1,0] = 7.0
matrixB[1,1] = 8.0

print(matrixA)
print(matrixB)

extension Matrix: Operation {

    mutating func sumWith(matrixB: Matrix) throws -> Matrix {

        guard self == matrixB else { throw RisedError.DimensionNotEquals }

        for row in 0...self.rows {
            for column in 0...self.columns {
                self[row, column] = matrixB[row, column] + self[row, column]
            }
        }
        return self
    }
}

do {
    try matrixA.sumWith(matrixB)
} catch RisedError.DimensionNotEquals {
    print("The two matrix's dimensions aren't equals")
} catch {
    print("Something very bad happens")
}

Here is the error Log:

解决方案

The problem is you're using the closed range operator in your for loop 0...self.rows. This will include the upper bound of the range in the iteration, which in your case is out of bounds and will therefore crash.

You want to use the half-open range operator ..< instead:

for row in 0..<self.rows {
    for column in 0..<self.columns {
        self[row, column] = matrixB[row, column] + self[row, column]
    }
}

This will iterate up to but not including the upper bound.

---

I would also note @MartinR's comment above – defining equality for the matrices to be solely based on the dimensions being the same seems illogical. Remember that equality implies substitutability (i.e if a == b, a and b are interchangeable).

I would consider changing your == to check both dimensions and values, and then implement your own dimension check in your sumWith method (or create a new method to compare dimensions).

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