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[java/runtime] non working interim commit of Metamodel classes
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| Overview of the Java translation of 6model | ||
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| In the 6model project, the java tree contains per-statement translations | ||
| of the C# files in the dotnet tree. C# is the "Microsoft Java" and this | ||
| subproject shows how close they are. | ||
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| Source formatting guidelines | ||
| ---------------------------- | ||
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| For clarity, or where there is doubt about the correctness of a | ||
| translation, include the original line afterwards in a comment. | ||
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| Add horizontal spacing to maximize correlation of text in consecutive | ||
| lines. | ||
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| With apologies to jnthn++, a case convention for the initial letter of | ||
| names is being gradually phased in. Class names, class member names and | ||
| interfaces is start with an uppercase letter. Local variables begin in | ||
| lowercase. | ||
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| C# to Java translation guidelines (sorted alphabetically, case insensitive) | ||
| --------------------------------------------------------------------------- | ||
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| C# bool becomes Java boolean. | ||
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| C# Dictionary becomes Java HashMap. The HashMap is not quite as | ||
| versatile, because the value part must be a reference type, it cannot be | ||
| a value type. Therefore C# Dictionary<string, int> becomes Java | ||
| HashMap<String, Integer> which it less convenient to use. | ||
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| C# internal access modifier becomes Java protected or public. | ||
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| C# Func<typelist> becomes a Java anonymous class that implements an | ||
| interface. | ||
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| C# InvalidOperationException becomes Java UnsupportedOperationException. | ||
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| C# lambda expressions (using => notation) become Java anonymous classes. | ||
| This is a lot of workaround writing because the anonymous classes | ||
| require an interface definition to implement, otherwise they inherit | ||
| from Object. | ||
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| C# Length (of an array) becomes Java length (of an array). | ||
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| C# Length (of a List) becomes Java size() (of an ArrayList). | ||
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| C# List becomes Java ArrayList. | ||
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| C# namespace yada { ... } becomes Java package yada; ... . | ||
| Also the Java package hierarchy must match the file system directory | ||
| hierarchy. | ||
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| C# NotImplementedException becomes Java NoSuchFieldException or | ||
| NoSuchMethodException. | ||
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| C# override does not become anything in Java (just delete it). | ||
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| C# sealed class becomes Java final class. Effect is not quite the same. | ||
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| C# string becomes Java String. | ||
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| C# using becomes Java import. In general, avoid the * (Whatever) form, | ||
| such as java.util.* because it is often useful to know exactly what is | ||
| being imported, for example java.util.HashMap or java.util.ArrayList. | ||
| The * is a form of programmer laziness which just shifts the problem on | ||
| to the next person or compiler who reads the program. We need clarity | ||
| here, not golf. | ||
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| Lambdas and References to Functions | ||
| ----------------------------------- | ||
| C# has some language features that Java currently lacks, to safely | ||
| provide what C and C++ call pointers to functions. | ||
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| The C# 'Func' generic type is a parameterized type. Variables declared | ||
| as 'Func<paramtype [,...], rettype>' store anonymous functions that take | ||
| certain parameters and return a certain result. Call the function using | ||
| the Invoke(...) method on the Func variable. | ||
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| The C# '=>' operator (also called Lambda) creates a reference to a block | ||
| of code. Store that reference in a Func variable. | ||
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| The C# 'delegate' type contains a collection of function pointers. When | ||
| the delegate is called, each function that is pointed to gets called in | ||
| an unspecified order. Useful for multicast notification, event handlers | ||
| and publish and subscribe architectures. | ||
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| The C# implementation of 6model uses the 'Func' and '=>' combination in | ||
| KnowHOWBoostrapper and RakudoCodeRef for example. The Java | ||
| implementation replaces the Func declaration with an IFunc_XXX interface | ||
| declaration that defines a suitably typed Invoke method, and replaces | ||
| the => with an anonymous class definition that implements that | ||
| interface. | ||
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| Created by: Martin Berends (mberends in #perl6 on irc.freenode.net) | ||
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