Crate fstrings_rust[][src]

::fstrings

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Basic fstring interpolation in Rust

The interpolation works as follows:

  1. if the (template) string literal contains a named parameter (e.g. {name})

  2. and no name = value argument is fed to the formatting call,

  3. then an automatic name = name argument is added, so that the variable is effectively interpolated from the current scope.

Example

#[macro_use]
extern crate fstrings;

fn main ()
{
    let name = "World";

    // Usage is simple: just append `_f` to the name of any formatting macro
    println_f!("Hello, {name}!");

    assert_eq!(
        f!("Hello, {name}!"), // shorthand for String creation (Python-like)
        String::from("Hello, World!"),
    );

    // ## Advanced cases:
    {
        // It remains compatible with classic formatting parameters
        assert_eq!(
            f!("{hi}, {name}!", hi = "Hello"),
            "Hello, World!",
        );

        // You can override / shadow the named arguments
        assert_eq!(
            f!("Hello, {name}!", name = "Earth"),
            "Hello, Earth!",
        );

        // You can use field access (but no method calls!)
        let foo = Foo { name }; /* where */ struct Foo<T> { name: T }
        assert_eq!(
            f!("Hello, {foo.name}!"),
            "Hello, World!",
        );

        // This also works with tuple indexing.
        let ft_and_name = (42, name);
        assert_eq!(
            f!("Hello, {ft_and_name.1}!"),
            "Hello, World!",
        );

        // You can use fstrings to debug by appending a `=` after the
        // interpolated expression.
        let x = 0b_101010;
        assert_eq!(
            f!("In this context {x=}"),
            "In this context x = 42",
        );
    }
}

Macros

debug_f

Shorthand for [debug!(format_f!].

eprint_f

Like eprint!, but with basic f-string interpolation.

eprintln_f

Like eprintln!, but with basic f-string interpolation.

error_f

Shorthand for [error!(format_f!].

f

Shorthand for format_f.

format_args_f

Like format_args!, but with basic f-string interpolation.

format_f

Like format!, but with basic f-string interpolation.

info_f

Shorthand for [info!(format_f!].

panic_f

Like panic!, but with basic f-string interpolation.

print_f

Like print!, but with basic f-string interpolation.

println_f

Like println!, but with basic f-string interpolation.

trace_f

Shorthand for [trace!(format_f!].

unimplemented_f

Like unimplemented!, but with basic f-string interpolation.

unreachable_f

Like unreachable!, but with basic f-string interpolation.

warn_f

Shorthand for [warn!(format_f!].

write_f

Like write!, but with basic f-string interpolation.

writeln_f

Like writeln!, but with basic f-string interpolation.