72 lines
1.8 KiB
Markdown
72 lines
1.8 KiB
Markdown
TaggedAlgebraic
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===============
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Implementation of a generic algebraic data type with a tagged union storage. All operations of the contained types are available for the `TaggedAlgebraic`
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[](https://travis-ci.org/s-ludwig/taggedalgebraic) [](https://coveralls.io/r/s-ludwig/taggedalgebraic?branch=master)
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Usage
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-----
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```d
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import taggedalgebraic;
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struct Foo {
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string name;
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void bar() {}
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}
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union Base {
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int i;
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string str;
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Foo foo;
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}
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alias Tagged = TaggedAlgebraic!Base;
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// Instantiate
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Tagged taggedInt = 5;
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Tagged taggedString = "Hello";
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Tagged taggedFoo = Foo();
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Tagged taggedAny = taggedInt;
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taggedAny = taggedString;
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taggedAny = taggedFoo;
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// Check type: Tagged.Kind is an enum
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assert(taggedInt.kind == Tagged.Kind.i);
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assert(taggedString.kind == Tagged.Kind.str);
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assert(taggedFoo.kind == Tagged.Kind.foo);
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assert(taggedAny.kind == Tagged.Kind.foo);
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// In most cases, can simply use as-is
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auto num = 4 + taggedInt;
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auto msg = taggedString ~ " World!";
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taggedFoo.bar();
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if (taggedAny.kind == Tagged.Kind.foo) // Make sure to check type first!
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taggedAny.bar();
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//taggedString.bar(); // AssertError: Not a Foo!
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// Convert back by casting
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auto i = cast(int) taggedInt;
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auto str = cast(string) taggedString;
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auto foo = cast(Foo) taggedFoo;
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if (taggedAny.kind == Tagged.Kind.foo) // Make sure to check type first!
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auto foo2 = cast(Foo) taggedAny;
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//cast(Foo) taggedString; // AssertError!
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// Kind is an enum, so final switch is supported:
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final switch (taggedAny.kind) {
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case Tagged.Kind.i:
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// It's "int i"
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break;
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case Tagged.Kind.str:
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// It's "string str"
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break;
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case Tagged.Kind.foo:
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// It's "Foo foo"
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break;
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}
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```
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