mirror of https://github.com/rust-lang/rust
148 lines
3.9 KiB
Rust
148 lines
3.9 KiB
Rust
//@ run-pass
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#![feature(macro_metavar_expr)]
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/// Count the number of idents in a macro repetition.
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macro_rules! count_idents {
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( $( $i:ident ),* ) => {
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${count($i)}
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};
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}
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/// Count the number of idents in a 2-dimensional macro repetition.
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macro_rules! count_idents_2 {
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( $( [ $( $i:ident ),* ] ),* ) => {
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${count($i)}
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};
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}
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/// Mostly counts the number of OUTER-MOST repetitions
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macro_rules! count_depth_limits {
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( $( { $( [ $( $outer:ident : ( $( $inner:ident )* ) )* ] )* } )* ) => {
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(
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(
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${count($inner)},
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${count($inner, 0)},
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${count($inner, 1)},
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${count($inner, 2)},
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${count($inner, 3)},
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),
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(
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${count($outer)},
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${count($outer, 0)},
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${count($outer, 1)},
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${count($outer, 2)},
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),
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)
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};
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}
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/// Produce (index, len) pairs for literals in a macro repetition.
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/// The literal is not included in the output, so this macro uses the
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/// `ignore` meta-variable expression to create a non-expanding
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/// repetition binding.
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macro_rules! enumerate_literals {
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( $( ($l:stmt) ),* ) => {
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[$( ${ignore($l)} (${index()}, ${len()}) ),*]
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};
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}
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/// Produce index and len tuples for literals in a 2-dimensional
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/// macro repetition.
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macro_rules! enumerate_literals_2 {
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( $( [ $( ($l:literal) ),* ] ),* ) => {
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[
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$(
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$(
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(
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${index(1)},
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${len(1)},
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${index(0)},
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${len(0)},
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$l
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),
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)*
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)*
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]
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};
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}
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/// Generate macros that count idents and then add a constant number
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/// to the count.
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///
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/// This macro uses dollar escaping to make it unambiguous as to which
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/// macro the repetition belongs to.
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macro_rules! make_count_adders {
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( $( $i:ident, $b:literal );* ) => {
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$(
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macro_rules! $i {
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( $$( $$j:ident ),* ) => {
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$b + $${count($j)}
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};
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}
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)*
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};
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}
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make_count_adders! { plus_one, 1; plus_five, 5 }
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/// Generate a macro that allows selection of a particular literal
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/// from a sequence of inputs by their identifier.
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///
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/// This macro uses dollar escaping to make it unambiguous as to which
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/// macro the repetition belongs to, and to allow expansion of an
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/// identifier the name of which is not known in the definition
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/// of `make_picker`.
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macro_rules! make_picker {
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( $m:ident => $( $i:ident ),* ; $p:ident ) => {
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macro_rules! $m {
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( $( $$ $i:literal ),* ) => {
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$$ $p
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};
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}
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};
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}
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make_picker!(first => a, b; a);
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make_picker!(second => a, b; b);
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fn main() {
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assert_eq!(count_idents!(a, b, c), 3);
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assert_eq!(count_idents_2!([a, b, c], [d, e], [f]), 6);
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assert_eq!(
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count_depth_limits! {
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{
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[ A: (a b c) D: (d e f) ]
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[ G: (g h) I: (i j k l m) ]
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[ N: (n) ]
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}
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{
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[ O: (o) P: (p q) R: (r s) ]
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[ T: (t u v w x y z) ]
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}
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},
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((26, 26, 9, 5, 2), (9, 9, 5, 2))
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);
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assert_eq!(enumerate_literals![("foo"), ("bar")], [(0, 2), (1, 2)]);
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assert_eq!(
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enumerate_literals_2![
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[("foo"), ("bar"), ("baz")],
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[("qux"), ("quux"), ("quuz"), ("xyzzy")]
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],
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[
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(0, 2, 0, 3, "foo"),
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(0, 2, 1, 3, "bar"),
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(0, 2, 2, 3, "baz"),
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(1, 2, 0, 4, "qux"),
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(1, 2, 1, 4, "quux"),
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(1, 2, 2, 4, "quuz"),
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(1, 2, 3, 4, "xyzzy"),
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]
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);
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assert_eq!(plus_one!(a, b, c), 4);
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assert_eq!(plus_five!(a, b), 7);
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assert_eq!(first!(1, 2), 1);
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assert_eq!(second!(1, 2), 2);
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}
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