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Documented fmt! expression syntax.

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Closes #3280
This commit is contained in:
Jesse Jones 2012-11-18 11:00:39 -08:00
parent d106ef88e6
commit d107e586ea
1 changed files with 40 additions and 1 deletions
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41
src/libcore/extfmt.rs
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@ -1,4 +1,40 @@
#[doc(hidden)];
//! Support for fmt! expressions.
//!
//! The syntax is close to that of Posix format strings:
//!
//! ~~~~~~
//! Format := '%' Parameter? Flag* Width? Precision? Type
//! Parameter := [0-9]+ '$'
//! Flag := [ 0#+-]
//! Width := Parameter | [0-9]+
//! Precision := '.' [0-9]+
//! Type := [bcdfiostuxX?]
//! ~~~~~~
//!
//! * Parameter is the 1-based argument to apply the format to. Currently not implemented.
//! * Flag 0 causes leading zeros to be used for padding when converting numbers.
//! * Flag # causes the conversion to be done in an *alternative* manner. Currently not implemented.
//! * Flag + causes signed numbers to always be prepended with a sign character.
//! * Flag - left justifies the result
//! * Width specifies the minimum field width of the result. By default leading spaces are added.
//! * Precision specifies the minimum number of digits for integral types and the minimum number
//! of decimal places for float.
//!
//! The types currently supported are:
//!
//! * b - bool
//! * c - char
//! * d - int
//! * f - float
//! * i - int (same as d)
//! * o - uint as octal
//! * t - uint as binary
//! * u - uint
//! * x - uint as lower-case hexadecimal
//! * X - uint as upper-case hexadecimal
//! * s - str (any flavor)
//! * ? - arbitrary type (does not use the to_str trait)
// NB: transitionary, de-mode-ing.
#[forbid(deprecated_mode)];
#[forbid(deprecated_pattern)];
@ -44,6 +80,7 @@ use option::{Some, None};
*/
// Functions used by the fmt extension at compile time
#[doc(hidden)]
pub mod ct {
pub enum Signedness { Signed, Unsigned, }
pub enum Caseness { CaseUpper, CaseLower, }
@ -277,6 +314,7 @@ pub mod ct {
// decisions made a runtime. If it proves worthwhile then some of these
// conditions can be evaluated at compile-time. For now though it's cleaner to
// implement it 0this way, I think.
#[doc(hidden)]
pub mod rt {
pub const flag_none : u32 = 0u32;
pub const flag_left_justify : u32 = 0b00000000000001u32;
@ -464,6 +502,7 @@ pub mod rt {
}
}
// Bulk of the tests are in src/test/run-pass/syntax-extension-fmt.rs
#[cfg(test)]
mod test {
#[test]