Declarative Object Identity via Key Modifier
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Programming languages often require substantial boilerplate code and are prone to bugs when overriding Equals and GetHashCode methods for custom object equality and identity, especially in scenarios where value semantics are needed, and do not provide a straightforward way to collapse notions of equality and identity outside of modifying the execution engine.
Innovation Solution
The introduction of declarative object identity support in programming languages through class declarations and object literals, where variables can be designated with modifiers like 'Key' to determine object identity and equality, leading to automatic implementation of Equals and GetHashCode methods that satisfy the required contract, with constraints ensuring immutability and recursive functions for reference types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If programmers manually override Equals and GetHashCode methods to define custom object equality, then value semantics can be achieved, but substantial boilerplate code is required and bugs are prone to be introduced
Solution Approach 1:
The compiler automatically generates the Equals and GetHashCode method implementations based on the Key modifier annotations in the class definition, eliminating the need for programmers to manually write these methods. The system serves itself by using the declared key variables to automatically produce correct equality semantics.
Solution Approach 2:
The Key modifier is declared in advance in the class definition, specifying which variables determine object identity and equality. This preliminary declaration allows the compiler to pre-generate the appropriate Equals and GetHashCode implementations without requiring manual coding at the point of use.
2Adaptability or versatility
If programmers manually override Equals and GetHashCode methods, then object equality can be customized, but the process is time-consuming and error-prone
Solution Approach 1:
The compiler automatically generates the Equals and GetHashCode method implementations based on the Key modifier annotations in the class definition, eliminating the need for programmers to manually write these methods. The system serves itself by using the declared key variables to automatically produce correct equality semantics.
Solution Approach 2:
The Key modifier is declared in advance in the class definition, specifying which variables determine object identity and equality. This preliminary declaration allows the compiler to pre-generate the appropriate Equals and GetHashCode implementations without requiring manual coding at the point of use.
3Ease of operation
If standard reference identity is used for objects, then object identity is straightforward to determine, but value semantics cannot be achieved for object equality
Solution Approach 1:
The Key modifier allows selective designation of specific variables within a class that determine equality semantics. Different variables can have different roles: Key-marked variables contribute to value-based equality, while other variables follow default reference identity behavior. This enables partial value semantics where only certain fields matter for equality.
Solution Approach 2:
The invention changes the parameter that determines equality from the default reference (memory address) to user-specified variables marked with the Key modifier. This parameter change allows the equality semantics to be customized based on which object fields are most important for determining equality in that specific context.
Data Source
AI summary
Systems and methods are described that enhance a programming language by introducing support for declarative object identity in both class declarations and object literals. An exemplary system includes a memory that stores code associated with a computer program and a component coupled to the memory. The component is configured to access the code, to identify a variable in the code and a modifier associated with the variable and, responsive to identifying the variable, to use the variable to determine the identity of an object associated with the variable and to determine whether the object is equal to another object based on value semantics.