C++ local variable destruction order
Within each category of storage classes (except dynamically allocated objects), objects are destructed in the reverse order of construction.
local-variables
UnboundLocalError trying to use a variable (supposed to be global) that is (re)assigned (even after first use)
Python treats variables in functions differently depending on whether you assign values to them from inside or outside the function. If a variable is assigned within a function, it is treated by default as a local variable. Therefore, when you uncomment the line, you are trying to reference the local variable c before any value … Read more
How to get local variables updated, when using the `exec` call?
This issue is somewhat discussed in the Python3 bug list. Ultimately, to get this behavior, you need to do: def foo(): ldict = {} exec(“a=3”,globals(),ldict) a = ldict[‘a’] print(a) And if you check the Python3 documentation on exec, you’ll see the following note: The default locals act as described for function locals() below: modifications to … Read more
Why do local variables require initialization, but fields do not?
Yuval and David’s answers are basically correct; summing up: Use of an unassigned local variable is a likely bug, and this can be detected by the compiler at low cost. Use of an unassigned field or array element is less likely a bug, and it is harder to detect the condition in the compiler. Therefore … Read more
Why is `a = a` `nil` in Ruby?
Ruby interpreter initializes a local variable with nil when it sees an assignment to it. It initializes the local variable before it executes the assignment expression or even when the assignment is not reachable (as in the example below). This means your code initializes a with nil and then the expression a = nil will … Read more
Why a variable defined global is undefined? [duplicate]
You have just stumbled on a js “feature” called hoisting var myname = “global”; // global variable function func() { alert(myname); // “undefined” var myname = “local”; alert(myname); // “local” } func(); In this code when you define func the compiler looks at the function body. It sees that you are declaring a variable called … Read more
Default values and initialization in Java
In the first code sample, a is a main method local variable. Method local variables need to be initialized before using them. In the second code sample, a is class member variable, hence it will be initialized to the default value.
Any way to modify locals dictionary?
I just tested exec and it works in Python 2.6.2 >>> def test(): … exec “a = 5” … print a … >>> test() 5 If you are using Python 3.x, it does not work anymore because locals are optimized as an array at runtime, instead of using a dictionary. When Python detects the “exec … Read more
Returning string from C function
Either allocate the string on the stack on the caller side and pass it to your function: void getStr(char *wordd, int length) { … } int main(void) { char wordd[10 + 1]; getStr(wordd, sizeof(wordd) – 1); … } Or make the string static in getStr: char *getStr(void) { static char wordd[10 + 1]; … return … Read more
“Life-time” of a string literal in C
Yes, lifetime of a local variable is within the scope({,}) in which it is created. Local variables have automatic or local storage. Automatic because they are automatically destroyed once the scope within which they are created ends. However, What you have here is an string literal, which is allocated in an implementation defined read-only memory. … Read more