Anonymous user
Call a function: Difference between revisions
→{{header|Rust}}: Added Rust
(→{{header|C}}: Added possible named argument implementation) |
(→{{header|Rust}}: Added Rust) |
||
Line 2,941:
p "%2d %4s" % [1,"xyz"] #=> " 1 xyz" "%2d %4s".%([1,"xyz"])</lang>
::Method call which was displayed in the comment is usable actually.
=={{header|Rust}}==
<lang rust>fn main() {
// Rust has a lot of neat things you can do with functions: let's go over the basics first
fn no_args() {}
// Run function with no arguments
no_args();
// Calling a function with fixed number of arguments.
// adds_one takes a 32-bit signed integer and returns a 32-bit signed integer
fn adds_one(num: i32) -> i32 {
// the final expression is used as the return value, though `return` may be used for early returns
num + 1
}
adds_one(1);
// Optional arguments
// The language itself does not support optional arguments, however, you can take advantage of
// Rust's algebraic types for this purpose
fn prints_argument(maybe: Option<i32>) {
match maybe {
Some(num) => println!("{}", num),
None => println!("No value given"),
};
}
prints_argument(Some(3));
prints_argument(None);
// You could make this a bit more ergonomic by using Rust's Into trait
fn prints_argument_into<I>(maybe: I)
where I: Into<Option<i32>>
{
match maybe.into() {
Some(num) => println!("{}", num),
None => println!("No value given"),
};
}
prints_argument_into(3);
prints_argument_into(None);
// Rust does not support functions with variable numbers of arguments. Macros fill this niche
// (println! as used above is a macro for example)
// Rust does not support named arguments
// We used the no_args function above in a no-statement context
// Using a function in an expression context
adds_one(1) + adds_one(5); // evaluates to eight
// Obtain the return value of a function.
let two = adds_one(1);
// In Rust there are no real built-in functions (save compiler intrinsics but these must be
// manually imported)
// In rust there are no such thing as subroutines
// In Rust, there are three ways to pass an object to a function each of which have very important
// distinctions when it comes to Rust's ownership model and move semantics. We may pass by
// value, by immutable reference, or mutable reference.
let mut v = vec![1, 2, 3, 4, 5, 6];
// By mutable reference
fn add_one_to_first_element(vector: &mut Vec<i32>) {
vector[0] += 1;
}
add_one_to_first_element(&mut v);
// By immutable reference
fn print_first_element(vector: &Vec<i32>) {
println!("{}", vector[0]);
}
print_first_element(&v);
// By value
fn consume_vector(vector: Vec<i32>) {
// We can do whatever we want to vector here
}
consume_vector(v);
// Due to Rust's move semantics, v is now inaccessible because it was moved into consume_vector
// and was then dropped when it went out of scope
// Partial application is not possible in rust without wrapping the function in another
// function/closure e.g.:
fn average(x: f64, y: f64) -> f64 {
(x + y) / 2.0
}
let average_with_four = |y| average(4.0, y);
average_with_four(2.0);
}</lang>
=={{header|Scala}}==
| |||