58 lines
1.6 KiB
Markdown
58 lines
1.6 KiB
Markdown
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Anonymous Functions
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===================
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{{#include ../links.md}}
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Sometimes it gets tedious to define separate functions only to dispatch them via single [function pointers].
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This scenario is especially common when simulating object-oriented programming ([OOP]).
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```rust
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// Define object
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let obj = #{
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data: 42,
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increment: Fn("inc_obj"), // use function pointers to
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decrement: Fn("dec_obj"), // refer to method functions
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print: Fn("print_obj")
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};
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// Define method functions one-by-one
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fn inc_obj(x) { this.data += x; }
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fn dec_obj(x) { this.data -= x; }
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fn print_obj() { print(this.data); }
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```
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The above can be replaced by using _anonymous functions_ which have the same syntax as Rust's closures
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(but they are **NOT** closures, merely syntactic sugar):
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```rust
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let obj = #{
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data: 42,
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increment: |x| this.data += x, // one-liner
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decrement: |x| this.data -= x,
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print_obj: || { print(this.data); } // full function body
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};
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```
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The anonymous functions will be hoisted into separate functions in the global namespace.
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The above is equivalent to:
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```rust
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let obj = #{
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data: 42,
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increment: Fn("anon_fn_1000"),
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decrement: Fn("anon_fn_1001"),
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print: Fn("anon_fn_1002")
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};
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fn anon_fn_1000(x) { this.data += x; }
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fn anon_fn_1001(x) { this.data -= x; }
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fn anon_fn_1002() { print this.data; }
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```
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WARNING - NOT Closures
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----------------------
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Remember: anonymous functions, though having the same syntax as Rust _closures_, are themselves
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**not** closures. In particular, they do not capture their running environment. They are more like
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Rust's function pointers.
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