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/*! Utility functions and macros Macros are accessible from the crate root: - `last!`, `next!`, `resume!` dirty macros - `anybox!` - (dev) `__unit!` and `__bool!` - (not exported) `maybe_match!` */ use crate::Maru; /** Shorthand for returning a ValRet::Ret # Example ``` use tear::{ValRet, ret}; fn f() -> ValRet<(), i8> { if true { ret!(72); } else { ValRet::Val(()) } } assert_eq![ f(), ValRet::Ret(72) ]; ``` */ #[macro_export] macro_rules! ret { ( $($v:tt)* ) => { return $crate::ValRet::Ret($($v)*); } } /** Dirty shortcut for creating a `Looping::Break` # Description If called with no arguments, it breaks the current loop. If called with the label index, it breaks the corresponding loop (see [`twist!`]). Used for writing short `twist!` statements that break from an enclosing loop. See examples. Note that this macro will fail to compile if `twist!` can break with a value or when using `twist -label`. # Examples ``` use tear::{twist, last}; loop { twist! { last!() } panic!("We should break before this") } 'a: loop { loop { twist! { -label 'a | last!(0) } panic!("We should break from the outer loop") } } ``` # Naming It is named after the equivalent of break in Perl. `break` is a keyword so we can't name the macro `break!` unless we use `r#break!`. # See also - [`last_if!`] */ #[macro_export] macro_rules! last { () => { $crate::Looping::Break::<_, $crate::BreakValError> { label: None } }; ( $id:expr ) => { $crate::Looping::Break::<_, $crate::BreakValError> { label: Some($id) } }; } /** Dirty shortcut for creating a `Looping::Continue` # Description If called with no arguments, it skips the current loop. If called with the label index, it skips the corresponding loop (see `twist!`). Used for writing short `twist!` statements that continue an enclosing loop. See examples. Note that this macro will fail to compile if `twist!` can break with a value or when using `twist -label`. # Examples ``` use tear::{twist, next}; let mut i = 0; loop { i += 1; if i < 5 { twist! { next!() } } break; } # assert_eq![ i, 5 ]; let mut i = 0; 'a: loop { i += 1; loop { if i < 8 { twist! { -label 'a | next!(0) } } break 'a; } } # assert_eq![ i, 8 ]; ``` # Naming It is named after the equivalent of continue in Perl. `continue` is a keyword so we can't name the macro `continue!` unless we use `r#continue!`. # See also - [`next_if!`] */ #[macro_export] macro_rules! next { () => { $crate::Looping::Continue::<_, $crate::BreakValError> { label: None } }; ( $id:expr ) => { $crate::Looping::Continue::<_, $crate::BreakValError> { label: Some($id) } }; } /** Dirty shortcut for creating a `Looping::Resume` # Description The only argument is the value to wrap in `Looping::Resume`. Used for writing short `twist!` statements that evaluate to a value. See examples. Note that this macro will fail to compile if `twist!` can break with a value or when using `twist -label`. # Examples ``` use tear::{twist, resume}; let mut i = 0; loop { i = twist! { resume!(7) }; break; } # assert_eq![ i, 7 ]; let mut i = 0; 'a: loop { loop { i = twist! { -label 'a | resume!(2) }; break 'a; } } # assert_eq![ i, 2 ]; ``` */ #[macro_export] macro_rules! resume { ( $($value:tt)* ) => { $crate::Looping::Resume::<_, $crate::BreakValError> ($($value)*) } } /** Turn a value into a `Box<dyn Any>` # Description Give it a value or an expression and it will turn it into a `Box<dyn Any>` value. Used for breaking multiple loops with different values types with `twist!`. # Examples Just wrapping the value and getting it back. ``` use tear::anybox; let boxed = anybox!(3); let x = match boxed.downcast::<i32>() { Ok(v) => *v, Err(_) => panic!("Failed to get the integer back."), }; assert_eq![ x, 3 ]; ``` Using it as the breakval with `twist!`. ``` use tear::{twist, anybox}; use tear::Looping; let e = Looping::BreakVal { label: Some(0), value: anybox!("a".to_string()) }; let x = 'a: loop { let _ = 'b: loop { twist! { -box -val i32, -label 'a: String | e } break 0; }; break "b".to_string(); }; assert_eq![ x, "a".to_string() ]; ``` */ #[macro_export] macro_rules! anybox { ( $e:expr ) => { { let v = $e; let b = Box::new(v); let x = b as Box<dyn core::any::Any>; x } } } /** (dev) Always expands to `()` Used for conditional expansion in macros as so. ```text $( __unit!($variable); $code )? ``` */ #[macro_export] macro_rules! __unit { ( $($whatever:tt)* ) => { () } } /** (dev) Always expands to `false` Used for conditional expansion of match arms in macros. `__bool!` expands to false so that the arm is never executed. ```text match $something { $( _ if __bool!($variable) => unreachable!(), $match-arm, )? ``` */ #[macro_export] macro_rules! __bool { ( $($whatever:tt)* ) => { false } } /** Executes match arm, or returns None Helper for writing enum accessors where you either match the correct pattern, or return None. The match arm expression is automatically wrapped into `Some`, so you don't need to. # Example ``` let x: Option<i32> = maybe_match! { "a", "a" => 3 }; assert_eq![ x, Some(3) ]; ``` */ macro_rules! maybe_match { ( $i:expr, $p:pat => $e:expr ) => { match $i { $p => Some($e), _ => None, } } } /** Always returns [`Maru`] This function is used with [`terror!`] to return None, where you would use `.ok()?.unwrap()` instead. ``` # use tear::prelude::*; fn f () -> Option<i32> { terror! { None => tear::gut } Some(1) } ``` */ pub fn gut<T> (_ :T) -> Maru { Maru }