pocketpy/docs/C-API/stack.md
BLUELOVETH 78ac9488ff ...
2023-07-18 12:17:26 +08:00

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---
title: Stack Manipulation
icon: dot
order: 8
---
### Basic manipulation
+ `bool pkpy_dup(pkpy_vm*, int)`
Duplicate the value at the given index.
+ `bool pkpy_pop(pkpy_vm*, int)`
Pop `n` values from the stack.
+ `bool pkpy_pop_top(pkpy_vm*)`
Pop the top value from the stack.
+ `bool pkpy_dup_top(pkpy_vm*)`
Duplicate the top value on the stack.
+ `bool pkpy_rot_two(pkpy_vm*)`
Swap the top two values on the stack.
+ `int pkpy_stack_size(pkpy_vm*)`
Get the element count of the stack.
### Basic push, check and convert
+ `pkpy_push_xxx` pushes a value onto the stack.
+ `pkpy_is_xxx` checks if the value at the given index is of the given type.
+ `pkpy_to_xxx` converts the value at the given index to the given type.
Stack index is 0-based instead of 1-based. And it can be negative, which means the index is counted from the top of the stack.
```c
// int
PK_EXPORT bool pkpy_push_int(pkpy_vm*, int);
PK_EXPORT bool pkpy_is_int(pkpy_vm*, int i);
PK_EXPORT bool pkpy_to_int(pkpy_vm*, int i, int* out);
// float
PK_EXPORT bool pkpy_push_float(pkpy_vm*, float);
PK_EXPORT bool pkpy_is_float(pkpy_vm*, int i);
PK_EXPORT bool pkpy_to_float(pkpy_vm*, int i, float* out);
// bool
PK_EXPORT bool pkpy_push_bool(pkpy_vm*, bool);
PK_EXPORT bool pkpy_is_bool(pkpy_vm*, int i);
PK_EXPORT bool pkpy_to_bool(pkpy_vm*, int i, bool* out);
// string
PK_EXPORT bool pkpy_push_string(pkpy_vm*, pkpy_CString);
PK_EXPORT bool pkpy_is_string(pkpy_vm*, int i);
PK_EXPORT bool pkpy_to_string(pkpy_vm*, int i, pkpy_CString* out);
// void_p
PK_EXPORT bool pkpy_push_voidp(pkpy_vm*, void*);
PK_EXPORT bool pkpy_is_voidp(pkpy_vm*, int i);
PK_EXPORT bool pkpy_to_voidp(pkpy_vm*, int i, void** out);
// none
PK_EXPORT bool pkpy_push_none(pkpy_vm*);
PK_EXPORT bool pkpy_is_none(pkpy_vm*, int i);
```
### Special push
+ `pkpy_push_null(pkpy_vm*)`
Push a `PY_NULL` onto the stack. It is used for `pkpy_vectorcall`.
+ `pkpy_push_function(pkpy_vm*, const char* sig, pkpy_CFunction f)`
Push a function onto the stack. `sig` is the function signature, e.g. `add(a: int, b: int) -> int`. `f` is the function pointer.
+ `pkpy_push_module(pkpy_vm*, const char* name)`
Push a new module onto the stack. `name` is the module name. This is not `import`. It creates a new module object.
### Variable access
+ `bool pkpy_getattr(pkpy_vm*, pkpy_CName name)`
Push `b.<name>` onto the stack.
```
[b] -> [b.<name>]
```
+ `bool pkpy_setattr(pkpy_vm*, pkpy_CName name)`
Set `b.<name>` to the value at the top of the stack.
First push the value, then push `b`.
```
[b, value] -> []
```
+ `bool pkpy_getglobal(pkpy_vm*, pkpy_CName name)`
Push a global variable onto the stack.
```
[] -> [value]
```
+ `bool pkpy_setglobal(pkpy_vm*, pkpy_CName name)`
Set a global variable to the value at the top of the stack.
```
[value] -> []
```
+ `bool pkpy_eval(pkpy_vm*, const char* source)`
Evaluate a string and push the result onto the stack.
```
[] -> [result]
```
+ `bool pkpy_unpack_sequence(pkpy_vm*, int size)`
Unpack a sequence at the top of the stack. `size` is the element count of the sequence.
```
[a] -> [a[0], a[1], ..., a[size - 1]]
```
+ `bool pkpy_get_unbound_method(pkpy_vm*, pkpy_CName name)`
It is used for method call.
Get an unbound method from the object at the top of the stack. `name` is the method name.
Also push the object as self.
```
[obj] -> [obj.<name> self]
```
+ `bool pkpy_py_repr(pkpy_vm*)`
Get the repr of the value at the top of the stack.
```
[value] -> [repr(value)]
```