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Minor fixes for the macros chapter #1113

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Merged
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Jan 19, 2019
Merged

Minor fixes for the macros chapter #1113

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449f00b
Remove an extra space character
nkaretnikov Nov 7, 2018
bb6fb9e
Reformat the comment to match the rest of the file
nkaretnikov Nov 7, 2018
81739b4
Add a comment about curly braces
nkaretnikov Nov 8, 2018
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6 changes: 3 additions & 3 deletions src/macros/dry.md
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ use std::ops::{Add, Mul, Sub};
macro_rules! assert_equal_len {
// The `tt` (token tree) designator is used for
// operators and tokens.
($a:ident, $b: ident, $func:ident, $op:tt) => (
($a:ident, $b:ident, $func:ident, $op:tt) => (
assert!($a.len() == $b.len(),
"{:?}: dimension mismatch: {:?} {:?} {:?}",
stringify!($func),
Expand Down Expand Up @@ -41,7 +41,7 @@ op!(sub_assign, Sub, -=, sub);
mod test {
use std::iter;
macro_rules! test {
($func: ident, $x:expr, $y:expr, $z:expr) => {
($func:ident, $x:expr, $y:expr, $z:expr) => {
#[test]
fn $func() {
for size in 0usize..10 {
Expand All @@ -57,7 +57,7 @@ mod test {
}
}

// Test `add_assign`, `mul_assign` and `sub_assign`
// Test `add_assign`, `mul_assign`, and `sub_assign`.
test!(add_assign, 1u32, 2u32, 3u32);
test!(mul_assign, 2u32, 3u32, 6u32);
test!(sub_assign, 3u32, 2u32, 1u32);
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3 changes: 3 additions & 0 deletions src/macros/dsl.md
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Expand Up @@ -39,3 +39,6 @@ Output:
This was a very simple example, but much more complex interfaces have been
developed, such as [`lazy_static`](https://crates.io/crates/lazy_static) or
[`clap`](https://crates.io/crates/clap).

Also, note the two pairs of braces in the macro. The outer ones are
part of the syntax of `macro_rules!`, in addition to `()` or `[]`.
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This is a little confusing to me – which "macro" are you referring to here? what is the "outer one"?

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The macro that's defined, there's only one. It's almost a copy-paste from the first edition of the book:

The outer braces are part of the syntax of macro_rules!. In fact, you can use () or [] instead.
They simply delimit the right-hand side as a whole.

I didn't link to the book since it's the first edition and RBE only references the second one, which doesn't cover this bit.

Would you prefer something like this?

Also, note the two pairs of braces in the macro definition [or: in the calculate definition]. The outer braces are part of the syntax ...

If not, feel free to suggest a better version. I think it's important to explain this syntax since it's the first time it is used in this book.

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@frewsxcv @steveklabnik why is this not going forward?