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https://github.com/pocketpy/pocketpy
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51 lines
1.5 KiB
Markdown
51 lines
1.5 KiB
Markdown
---
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icon: dot
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label: 'Bind native function'
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order: 60
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---
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In `VM` class, there are 4 methods to bind native function.
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+ `VM::bind_func<ARGC>`
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+ `VM::bind_builtin_func<ARGC>`
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+ `VM::bind_method<ARGC>`
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+ `VM::bind_static_method<ARGC>`
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They are all template methods, the template argument is a `int` number, indicating the argument count. For variadic arguments, use `-1`. For methods, `ARGC` do not include `self`.
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!!!
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Native functions do not support keyword arguments.
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!!!
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pkpy uses a universal C function pointer for native functions:
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```cpp
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typedef PyObject* (*NativeFuncC)(VM*, ArgsView);
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```
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The first argument is the pointer of `VM` instance.
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The second argument is a view of an array. You can use `[]` operator to get the element. If you have specified `ARGC` other than `-1`, the interpreter will ensure `args.size() == ARGC`. No need to do size check.
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The return value is a `PyObject*`, which should not be `nullptr`. If there is no return value, return `vm->None`.
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This is an example of binding the `input()` function to the `builtins` module.
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```cpp
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VM* vm = pkpy_new_vm();
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vm->bind_builtin_func<0>("input", [](VM* vm, ArgsView args){
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static std::string line;
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std::getline(std::cin, line);
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return VAR(line);
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});
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// vvv function name
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vm->bind_builtin_func<2>("add", [](VM* vm, ArgsView args){
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// ^ argument count
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i64 lhs = CAST(i64, args[0]);
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i64 rhs = CAST(i64, args[1]);
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return VAR(lhs + rhs);
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});
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``` |