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How do I declare an instance of one of my Rust structs as static? [duplicate]
(1 answer)
How can you make a safe static singleton in Rust?
(3 answers)
How do I create a global, mutable singleton?
(7 answers)
Closed 4 years ago.
I need to have a static std::string::String . I tried initializing it in several ways but in vain. One of them being -
static mut DURATION_HEX:String = "0".to_string();
I get a note saying :
note: a limited form of compile-time function evaluation is available
on a nightly compiler via const fn
I am not able to initialize it. I cannot leave it without initialization as well.
How do I create a static variable of non-primitive type in rust?
Related
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Why declare a variable or function static in C?
(4 answers)
Closed 3 years ago.
I have learned that those global variables that will not be used outside the file should be made non-global variable by appending static keyword like static int a;
I want to know that why we should do this?
Static implies a translation unit level scope only.
However, you don't need to make it non-global + static.
You can very well make it global static to curb the scope to translation unit level.
This question already has answers here:
Complex C declaration
(8 answers)
Closed 4 years ago.
I wonder how to read a complex definition like that
int (*(*a())[]) ()) ;
And what is the order of reading such definitions ?
Check this out: https://cdecl.org/. It's a handy tool if you're new at reading these types of functions.
This question already has answers here:
What does "static" mean in C?
(20 answers)
Closed 5 years ago.
If I apply static keyword to local variable, its value is maintained within function invocations. However, if I apply static keyword to global variable, will it be as good as declaring the variable as global? What I mean to say is does static keyword has any effect on global variables?
It means that variable has file scope. You cannot access that global variable (by name) from another file.
This question already has answers here:
How do you declare string constants in C?
(5 answers)
"static const" vs "#define" vs "enum"
(17 answers)
Closed 5 years ago.
I have a string: "The world is a beautiful place to live in.".
I have two source files and a global header file. I can access the string in two easy ways:-
Declaring and defining a constant variable as shown: I can use it using extern
const char *str = "The world is a beautiful place to live in.";
Using #define STR "The world is a beautiful place to live in."
Out of the above two options, which one is preferred in C?
It doesn't matter (doesn't matter if you only consider of getting a string literal) how you do but in case you want to get the string constant to be traced under debugger you may want to use the const char*str = ...
With macro definition you will get all the problems of macro
expansion- the side effects of the expanson, the pollution of the name
space, the deviation from debugger help etc
This question already has answers here:
Static function variables in Swift
(4 answers)
Closed 8 years ago.
How can I have a static variable within a function as shown below?
func addItem(petItem:Item) -> Bool {
var static count = 0 //... pseudo code
...
...Or must I have all static codes at the top of the file (global area)?
Or must I have all static codes at the top of the file (global area)?
Yep, that. You need to declare your variable in the scope where it will persist. Exactly where that should be depends on what you are trying to achieve.