macro_rules! column {
() => { ... };
}Expand description
Expands to the column number at which it was invoked.
With line! and file!, these macros provide debugging information for
developers about the location within the source.
The expanded expression has type u32 and is 1-based, so the first column
in each line evaluates to 1, the second to 2, etc. This is consistent
with error messages by common compilers or popular editors.
The returned column is not necessarily the line of the column! invocation itself,
but rather the first macro invocation leading up to the invocation
of the column! macro.
Examples
let current_col = column!();
println!("defined on column: {}", current_col);column! counts Unicode code points, not bytes or graphemes. As a result, the first two
invocations return the same value, but the third does not.
let a = ("foobar", column!()).1;
let b = ("人之初性本善", column!()).1;
let c = ("f̅o̅o̅b̅a̅r̅", column!()).1; // Uses combining overline (U+0305)
assert_eq!(a, b);
assert_ne!(b, c);