[−][src]Macro const_format::formatcp
Formats constants of primitive types into a &'static str
formatcp
stands for "format constants (of) primitives"
Syntax
This macro uses a limited version of the syntax from the standard library format
macro,
it can do these things:
-
Take positional arguments:
formatcp!("{}{0}", "hello" )
-
Take named arguments:
formatcp!("{a}{a}", a = "hello" )
-
Use constants from scope as arguments:
formatcp!("{FOO}")
, equivalent to theformat_args_implicits
RFC -
Use Debug-like formatting (eg:
formatcp!("{:?}", "hello" ): Similar to how Debug formatting in the standard library works, except that it does not escape unicode characters.
-
Use Hexsadecimal formatting (eg:
formatcp!("{:x}", "hello" )
): Formats numbers as capitalized hexadecimal, The alternate version (written as"{:#x}"
), prefixes the number with0x
-
Use Binary formatting (eg:
formatcp!("{:b}", "hello" )
). The alternate version (written as"{:#b}"
), prefixes the number with0b
-
Use Display formatting:
formatcp!("{}", "hello" )
Limitations
This macro can only take constants of these types as inputs:
-
&str
-
i*
/u*
(all the primitive integer types). -
bool
This macro also shares the limitations described in here as well.
Format specifiers
Debug-like
The {:?}
formatter formats things similarly to how Debug does it.
For &'static str
it does these things:
- Prepend and append the double quote character (
"
). - Escape the
'\t'
,'\n'
,'\r'
,'\\'
,'\''
, and'\"'
characters. - Escape control characters with
\xYY
, whereYY
is the hexadecimal value of the control character.
Example:
use const_format::formatcp; assert_eq!(formatcp!("{:?}", r#" \ " ó "#), r#"" \\ \" ó ""#);
Display
The {}
/{:}
formatter works the same as in format
.
Examples
Implicit argument
use const_format::formatcp; const NAME: &str = "John"; const MSG: &str = formatcp!("Hello {NAME}, your name is {} bytes long", NAME.len()); assert_eq!(MSG, "Hello John, your name is 4 bytes long");
Repeating arguments
use const_format::formatcp; const MSG: &str = formatcp!("{0}{S}{0}{S}{0}", "SPAM", S = " "); assert_eq!(MSG, "SPAM SPAM SPAM");
Debug-like and Display formatting
use const_format::formatcp; const TEXT: &str = r#"hello " \ world"#; const MSG: &str = formatcp!("{TEXT}____{TEXT:?}"); assert_eq!(MSG, r#"hello " \ world____"hello \" \\ world""#);