hygiene

Can someone explain the concept of 'hygiene' to me (I'm a scheme programmer)?

由 若如初见. 提交于 2020-07-04 20:15:33
问题 So... I'm new to scheme r6rs, and am learning macros. Can somebody explain to me what is meant by 'hygiene'? Thanks in advance. 回答1: Hygiene is often used in the context of macros. A hygienic macro doesn't use variable names that can risk interfering with the code under expansion. Here is an example. Let's say we want to define the or special form with a macro. Intuitively, (or a b c ... d) would expand to something like (let ((tmp a)) (if tmp a (or b c ... d))) . (I am omitting the empty (or

How can I create hygienic identifiers in code generated by procedural macros?

由 谁都会走 提交于 2020-01-13 09:25:12
问题 When writing a declarative ( macro_rules! ) macro, we automatically get macro hygiene . In this example, I declare a variable named f in the macro and pass in an identifier f which becomes a local variable: macro_rules! decl_example { ($tname:ident, $mname:ident, ($($fstr:tt),*)) => { impl std::fmt::Display for $tname { fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { let Self { $mname } = self; write!(f, $($fstr),*) } } } } struct Foo { f: String, } decl_example!(Foo, f,

Collection of Great Applications and Programs using Macros

由 泪湿孤枕 提交于 2019-12-17 17:28:19
问题 I am very very interested in Macros and just beginning to understand its true power. Please help me collect some great usage of macro systems. So far I have these constructs: Pattern Matching: Andrew Wright and Bruce Duba. Pattern matching for Scheme, 1995 Relations in the spirit of Prolog: Dorai Sitaram. Programming in schelog. http://www.ccs.neu.edu/home/dorai/schelog/schelog.html Daniel P. Friedman, William E. Byrd, and Oleg Kiselyov. The Reasoned Schemer. The MIT Press, July 2005 Matthias

Why does macro hygiene not prevent collisions between multiple const definitions?

由 故事扮演 提交于 2019-12-04 04:46:15
问题 I thought "hygiene" would prevent collisions between X s defined within my macro m! but that turned out not to be the case. What am I misunderstanding? macro_rules! m { ($e:expr) => { const X: i32 = $e; }; } m!(0); m!(1); fn main() { m!(2); m!(3); } Playground Error message: error[E0428]: the name `X` is defined multiple times --> src/main.rs:3:9 | 3 | const X: i32 = $e; | ^^^^^^^^^^^^^^^^^^ | | | `X` redefined here | previous definition of the value `X` here ... 7 | m!(0); | ------ in this

Collection of Great Applications and Programs using Macros

由 我与影子孤独终老i 提交于 2019-11-28 02:49:07
I am very very interested in Macros and just beginning to understand its true power. Please help me collect some great usage of macro systems. So far I have these constructs: Pattern Matching: Andrew Wright and Bruce Duba. Pattern matching for Scheme, 1995 Relations in the spirit of Prolog: Dorai Sitaram. Programming in schelog. http://www.ccs.neu.edu/home/dorai/schelog/schelog.html Daniel P. Friedman, William E. Byrd, and Oleg Kiselyov. The Reasoned Schemer. The MIT Press, July 2005 Matthias Felleisen. Transliterating Prolog into Scheme. Technical Report 182, Indiana University, 1985.
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