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#pragma once
// generator/continuation for C++
// author: Andrew Fedoniouk @ terrainformatica.com
// idea borrowed from: "coroutines in C" Simon Tatham,
// http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html
// BSD license
template<typename T>
struct _generator
{
T* _stack;
int _line;
_generator():_stack(0), _line(-1) {}
void _push() { T* n = new T; *n = *static_cast<T*>(this); _stack = n; }
bool _pop() { if(!_stack) return false; T* t = _stack; *static_cast<T*>(this) = *_stack; t->_stack = 0; delete t; return true; }
~_generator() { while(_pop()); }
};
#define $generator(NAME) struct NAME : public _generator<NAME>
#define $emit(T) bool operator()(T& _rv) { \
if(_line < 0) _line=0; \
$START: switch(_line) { case 0:;
#define $stop } _line = 0; if(_pop()) goto $START; return false; }
#define $restart(WITH) { _push(); _stack->_line = __LINE__; _line=0; WITH; goto $START; case __LINE__:; }
#define $yield(V) \
do {\
_line=__LINE__;\
_rv = (V); return true; case __LINE__:;\
} while (0)
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