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Operating Systems Achyut S Godbole Tata Mcgraw Hill 2nd Editionrar [Updated] 2022







Q: How do I use Kotlin to type check an enum type? I am trying to write a function that takes an Enum type and returns the integer that is listed in the enum. For example, this works: fun sumOfEnum(enum: MyEnum): Int { for (e in enum) { when (e) { MyEnum.ZERO -> return 0 MyEnum.ONE -> return 1 MyEnum.TWO -> return 2 } } } But I want to make this function type-safe, so that it doesn't compile if someone uses the function on an enum that isn't defined in the enumeration. I tried using the? syntax to try to make this work: fun sumOfEnum(enum: MyEnum?): Int { for (e in enum) { when (e) { MyEnum.ZERO -> return 0 MyEnum.ONE -> return 1 MyEnum.TWO -> return 2 } } } But this causes a compile error: Type mismatch. Required: MyEnum? Found: MyEnum How do I write the function so that it will return a default value if the enum isn't defined in the enumeration? A: You can use one of these two approaches: Use a common base type for your enum values, say Int, and create a function sumOfEnum2(enum: MyEnum2): Int that sums all values of an enum whose type extends MyEnum2. Create a map of enum values to their values, using the values of MyEnum. Then create a function sumOfEnum3(enum: MyEnum): Int that sums all values of enum that are mapped to a specific value, as defined in the Enum ac619d1d87


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