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Closure blocks in C++
/*
http://en.wikipedia.org/wiki/C_Sharp_syntax#Closure_blocks
C#
public void Foo()
{
using (var bar = File.Open("Foo.txt"))
{
// do some work
throw new Exception();
// bar will still get properly disposed.
}
}
Python
with open("x.txt") as f:
data = f.read()
*/
#include <cstdio>
class Foo {
public:
Foo() { printf("construct\n"); }
~Foo() { printf("destructor\n"); }
void call() { printf("call\n"); }
};
#define WITH_COND_VAR(LINE) __with_run_##LINE
#define WITH_FOR(EXPR, LINE) \
int WITH_COND_VAR(LINE) = false; \
for(EXPR ; WITH_COND_VAR(LINE) == false ; WITH_COND_VAR(LINE) = true)
#define WITH(EXPR) WITH_FOR(EXPR, __LINE__)
int main()
{
// legacy
printf("legacy block\n");
{
Foo foo;
foo.call();
}
// closure-block
printf("closure block - 1\n");
WITH(Foo foo) {
foo.call();
}
printf("closure block - 2\n");
WITH(Foo foo) {
foo.call();
}
return 0;
}
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