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29 lines
1.0 KiB
Markdown
29 lines
1.0 KiB
Markdown
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title = "Functional operations"
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weight = 5
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sort_by = "weight"
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in_search_index = true
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+++
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UCG comes with some builtin functional operations.
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## Useful functions
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* identity - the Identity function. Returns it's argument unchanged.
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## Maybe module
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Maybe is a monadic style wrapper for values that might be NULL. It provides a several operations for the wrapped value.
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* do(op) - runs op which is a function of one argument against the wrapped value if it is not null. Returns the result or NULL wrapped in another maybe.
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* or(op) - runs op which is a function of no arguments if the wrapped value is null. Returns the result wrapped in another maybe.
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* is_null() - returns true if the wrapped value is null, false otherwise.
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* unwrap() - returns the wrapped value
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* expect(msg) - returns the wrapped value if it is not null. Throws a compile error with the user provided message otherwise.
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```
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let maybe = import "std/functional.ucg".maybe;
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let result = maybe{val=NULL}.or(func () => "foo").do(func(v) => v + "bar");
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result == "foobar";
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``` |