Updated the subscript check to use preconditions instead of a custom function.

Author: kelvinlauKL

Array2D/Array2D.playground/Contents.swift

@@ -11,29 +11,21 @@ public struct Array2D<T> {
   public init(columns: Int, rows: Int, initialValue: T) {
     self.columns = columns
     self.rows = rows
-    array = [T](repeating: initialValue, count: rows*columns)
+    array = .init(repeating: initialValue, count: rows*columns)
   }
 
   public subscript(column: Int, row: Int) -> T {
     get {
-      if isValidSubscript(column: column, row: row) {
-        return array[row*columns + column]
-      } else {
-        fatalError("Not a valid subscript")
-      }
+      precondition(column < columns, "Column \(column) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      precondition(row < rows, "Row \(row) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      return array[row*columns + column]
     }
     set {
-      if isValidSubscript(column: column, row: row) {
-        array[row*columns + column] = newValue
-      } else {
-        fatalError("Not a valid subscript")
-      }
+      precondition(column < columns, "Column \(column) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      precondition(row < rows, "Row \(row) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      array[row*columns + column] = newValue
     }
   }
-  
-  private func isValidSubscript(column: Int, row: Int) -> Bool {
-    return column < columns && row < rows
-  }
 }
 
 

Array2D/Array2D.swift

@@ -7,21 +7,22 @@ public struct Array2D<T> {
   public let columns: Int
   public let rows: Int
   fileprivate var array: [T]
-
+  
   public init(columns: Int, rows: Int, initialValue: T) {
     self.columns = columns
     self.rows = rows
     array = .init(repeating: initialValue, count: rows*columns)
   }
-
+  
   public subscript(column: Int, row: Int) -> T {
     get {
+      precondition(column < columns, "Column \(column) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      precondition(row < rows, "Row \(row) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
       return array[row*columns + column]
     }
     set {
-      precondition(row < rows, "Row \(row) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
       precondition(column < columns, "Column \(column) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
-        
+      precondition(row < rows, "Row \(row) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
       array[row*columns + column] = newValue
     }
   }

Array2D/README.markdown

@@ -72,29 +72,21 @@ public struct Array2D<T> {
   public init(columns: Int, rows: Int, initialValue: T) {
     self.columns = columns
     self.rows = rows
-    array = [T](repeating: initialValue, count: rows*columns)
+    array = .init(repeating: initialValue, count: rows*columns)
   }
 
   public subscript(column: Int, row: Int) -> T {
     get {
-      if isValidSubscript(column: column, row: row) {
-        return array[row*columns + column]
-      } else {
-        fatalError("Not a valid subscript")
-      }
+      precondition(column < columns, "Column \(column) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      precondition(row < rows, "Row \(row) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      return array[row*columns + column]
     }
     set {
-      if isValidSubscript(column: column, row: row) {
-        array[row*columns + column] = newValue
-      } else {
-        fatalError("Not a valid subscript")
-      }
+      precondition(column < columns, "Column \(column) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      precondition(row < rows, "Row \(row) Index is out of range. Array<T>(columns: \(columns), rows:\(rows))")
+      array[row*columns + column] = newValue
     }
   }
-  
-  private func isValidSubscript(column: Int, row: Int) -> Bool {
-    return column < columns && row < rows
-  }
 }
 ```