eval and exec are handy quick-and-dirty way to get some source code dynamically, maybe munge it a bit, and then execute it — but they’re hardly ever the best way, especially in production code as opposed to “quick-and-dirty” prototypes &c. For example, if I had to deal with such dynamic Python sources, I’d reach for … Read more
You need to use single quotes to prevent interpolation happening in your calling shell. $ bash -c ‘echo arg 0: $0, arg 1: $1’ arg1 arg2 arg 0: arg1, arg 1: arg2 Or escape the variables in your double-quoted string. Which to use might depend on exactly what you want to put in your snippet … Read more
C++ doesn’t have reflection so you must hack it, i. e.: #include <iostream> #include <map> #include <string> #include <functional> void foo() { std::cout << “foo()”; } void boo() { std::cout << “boo()”; } void too() { std::cout << “too()”; } void goo() { std::cout << “goo()”; } int main() { std::map<std::string, std::function<void()>> functions; functions[“foo”] = … Read more
The consensus of the Perl community seems to be that Try::Tiny is the preferred way of doing exception handling. The “lenient policy” you refer to is probably due to a combination of: Perl not being a fully object-oriented language. (e.g. in contrast to Java where you can’t avoid dealing with exceptions.) The background of many … Read more
eval() will allow malicious data to compromise your entire system, kill your cat, eat your dog and make love to your wife. There was recently a thread about how to do this kind of thing safely on the python-dev list, and the conclusions were: It’s really hard to do this properly. It requires patches to … Read more
I am completely against this use of __code__. Although I am a curious person, and this is what someone theoretically could do: code # This is your code object that you want to execute def new_func(eggs): pass new_func.__code__ = code new_func(‘eggs’) Again, I never want to see this used, ever. You might want to look … Read more
Javascript is a very flexible language in this regard. There are very very few cases where eval() is the right answer to any given question, and it certainly isn’t necessary here. If your a and b variables are part of an object, you can access them with string subscripts: ie myobj.a could also be referenced … Read more
(load-string “(+ 1 2)”)