Document the parsing macros

[dtolnay]

Before including this in a release, I would like to document all of the parsers with realistic procedural-macro-appropriate examples. @mystor would you be able to help me work through these?

• alt
• call
• cond
• cond_reduce
• delimited
• do_parse
• epsilon
• keyword
• many0
• map
• named
• not
• opt_vec
• option
• peek
• preceded
• punct
• separated_list
• separated_nonempty_list
• switch
• tag
• take_until
• terminated
• terminated_list
• tuple
• value

I started you off with two examples of what I have in mind but feel free to invent your own approach if you want.

One or more of something separated by some separator.

• Syntax: separated_nonempty_list!(SEPARATOR, THING)
• Output: Vec<THING>

extern crate syn;
#[macro_use] extern crate synom;

use syn::Ty;
use syn::parse::ty;

// One or more Rust types separated by commas.
named!(comma_separated_types -> Vec<Ty>,
    separated_nonempty_list!(
        punct!(","),
        ty));

fn main() {
    let input = "&str, Map<K, V>, String";

    let parsed = comma_separated_types(input).expect("comma-separated types");

    assert_eq!(parsed.len(), 3);
    println!("{:?}", parsed);
}

---

Value surrounded by a pair of delimiters.

• Syntax: delimited!(OPEN, THING, CLOSE)
• Output: THING

extern crate syn;
#[macro_use] extern crate synom;

use syn::Expr;
use syn::parse::expr;

// An expression surrounded by [[ ... ]].
named!(double_bracket_expr -> Expr,
    delimited!(
        punct!("[["),
        expr,
        punct!("]]")));

fn main() {
    let input = "[[ 1 + 1 ]]";

    let parsed = double_bracket_expr(input).expect("double bracket expr");

    println!("{:?}", parsed);
}

[dtolnay]

Fixed in #91 and #93.