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Higher-order rust macro that assists in parsing by macro
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/// Higher-order macro fold function for pre-parsing comma separated lists | |
/// | |
/// The commas on KEYWORD lines can be changed to parse lists with any | |
/// separator. | |
/// run a macro on a list of lists after splitting the input at commas | |
macro_rules! split_comma { | |
// no defaults | |
{$fun:ident <= $($item:tt)*} => { | |
split_comma![$fun () () () <= $($item)*] | |
}; | |
// give initial params to the function | |
{$fun:ident ($($first:tt)*) <= $($item:tt)*} => { | |
split_comma![$fun ($($first)*) () () <= $($item)*] | |
}; | |
// give inital params and initial inner items in every group | |
{$fun:ident ($($first:tt)*) ($($every:tt)*) <= $($item:tt)*} => { | |
split_comma![$fun ($($first)*) ($($every)*) ($($every)*) <= $($item)*] | |
}; | |
// KEYWORD line | |
// on non-final seperator, stash the accumulator and restart it | |
{$fun:ident ($($first:tt)*) ($($every:tt)*) ($($current:tt)*) <= , $($item:tt)+} => { | |
split_comma![$fun ($($first)* ($($current)*)) ($($every)*) ($($every)*) <= $($item)*] | |
}; | |
// KEYWORD line | |
// ignore final seperator, run the function | |
{$fun:ident ($($first:tt)*) ($($every:tt)*) ($($current:tt)+) <= , } => { | |
$fun![$($first)* ($($current)*)] | |
}; | |
// on next item, add it to the accumulator | |
{$fun:ident ($($first:tt)*) ($($every:tt)*) ($($current:tt)*) <= $next:tt $($item:tt)*} => { | |
split_comma![$fun ($($first)*) ($($every)*) ($($current)* $next) <= $($item)*] | |
}; | |
// at end of items, run the function | |
{$fun:ident ($($first:tt)*) ($($every:tt)*) ($($current:tt)+) <= } => { | |
$fun![$($first)* ($($current)*)] | |
}; | |
// if there were no items and no default, run with only initial params, if any | |
{$fun:ident ($($first:tt)*) () () <= } => { | |
$fun![$($first)*] | |
}; | |
} | |
// Macros passed to `split_comma` take optional initial parameters followed by a list of | |
// parenthesised items. These outer parentheses now separate what was originally separated | |
// by commas. | |
macro_rules! sum_vec { | |
{$(($($item:tt)*))*} => { vec![$(0 $(+ $item )*, )*] }; | |
{debug $($item:tt)*} => { stringify![$($item)*].to_string() }; | |
} | |
fn main(){ | |
let x = split_comma![sum_vec <= 1 2, 3 4, 5 6]; | |
println!("{:?}",x); | |
// [3, 7, 11] | |
let x = split_comma![sum_vec (debug) (hi) <= 4 5,7,,1 2 3,]; | |
println!("{:?}",x); | |
// "( hi 4 5 ) ( hi 7 ) ( hi ) ( hi 1 2 3 )" | |
let hi = 8; | |
let x = split_comma![sum_vec () (hi) <= 4 5,7,,1 2 3]; | |
println!("{:?}",x); | |
// [17, 15, 8, 14] | |
let x = split_comma![sum_vec (debug) <= ]; | |
println!("{:?}",x); | |
// "" | |
} |
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