A parser library designed for Advent of Code.
This library mainly provides a macro, parser!, that lets you write
a custom parser for your [AoC] puzzle input in seconds.
For example, my puzzle input for December 2, 2015 looked like this:
4x23x21
22x29x19
11x4x11
8x10x5
24x18x16
...
The parser for this format is a one-liner:
parser!(lines(u64 "x" u64 "x" u64)).
It's pretty easy.
```rust use aoc_parse::{parser, prelude::*};
let p = parser!(lines(u64 "x" u64 "x" u64)); assert_eq!( p.parse("4x23x21\n22x29x19\n").unwrap(), vec![(4, 23, 21), (22, 29, 19)] ); ```
If you're using [aoc-runner], it might look like this:
```rust use aocrunnerderive::; use aoc_parse::{parser, prelude::};
fn parse_input(text: &str) -> Vec<(u64, u64, u64)> { let p = parser!(lines(u64 "x" u64 "x" u64)); p.parse(text).unwrap() } ```
The argument you need to pass to the parser! macro is a pattern;
all aoc-parse does is match strings against your chosen pattern
and convert them into Rust values.
Here are some examples of patterns:
```rust
lines(i32) // matches a list of integers, one per line
// converts them to a Vec
line(lower+) // matches a single line of one or more lowercase letters
// converts them to a Vec
lines({ // matches lines made up of the characters < = >
"<" => -1, // converts them to a Vec
Here are the pieces that you can use in a pattern:
i8, i16, i32, i64, i128, isize - These match an integer,
written out using decimal digits, with an optional + or - sign
at the start, like 0 or -11474.
It's an error if the string contains a number too big to fit in the
type you chose. For example, parser!(i8).parse("1000") is an error.
(It matches the string, but fails during the "convert" phase.)
u8, u16, u32, u64, u128, usize - The same, but without
the sign.
i8_bin, i16_bin, i32_bin, i64_bin, i128_bin, isize_bin,
u8_bin, u16_bin, u32_bin, u64_bin, u128_bin, usize_bin,
i8_hex, i16_hex, i32_hex, i64_hex, i128_hex, isize_hex,
u8_hex, u16_hex, u32_hex, u64_hex, u128_hex, usize_hex -
Match an integer in base 2 or base 16. The _hex parsers allow both
uppercase and lowercase digits A-F.
bool - Matches either true or false and converts it to the
corresponding bool value.
alpha, alnum, upper, lower - Match single characters of
various categories. (These use the Unicode categories, even though
Advent of Code historically sticks to ASCII.)
digit, digit_bin, digit_hex - Match a single ASCII character
that's a digit in base 10, base 2, or base 16, respectively.
The digit is converted to its numeric value, as a usize.
any_char: Match the next character, no matter what it is (like .
in a regular expression, except that any_char matches newline
characters).
'x' or "hello" - A Rust character or string, in quotes, is a pattern
that matches that exact text only.
Exact patterns don't produce a value.
pattern1 pattern2 pattern3... - Patterns can be
concatenated to form larger patterns. This is how
parser!(u64 "x" u64 "x" u64) matches the string 4x23x21. It simply
matches each subpattern in order. It converts the match to a tuple if
there are two or more subpatterns that produce values.
parser_var - You can use previously defined
parsers that you've stored in local variables.
For example, the amount parser below makes use of the fraction parser
defined on the previous line.
``` let fraction = parser!(i64 "/" u64); let amount = parser!(fraction " tsp");
assert_eq!(amount.parse("1/4 tsp").unwrap(), (1, 4)); ```
An identifier can also refer to a string or character constant.
string(pattern) - Matches the given pattern,
but instead of converting it to some value, simply return the matched
characters as a String.
By default, alpha+ returns a Vec<char>, and sometimes that is handy
in AoC, but often it's better to have it return a String.
Repeating patterns:
pattern* - Any pattern followed by an asterisk
matches that pattern zero or more times. It converts the results to a
Vec. For example, parser!("A"*) matches the strings A, AA,
AAAAAAAAAAAAAA, and so on, as well as the empty string.
pattern+ - Matches the pattern one or more times, producing a Vec.
parser!("A"+) matches A, AA, etc., but not the empty string.
pattern? - Optional pattern, producing a Rust Option. For
example, parser!("x=" i32?) matches x=123, producing Some(123);
it also matches x=, producing the value None.
These behave just like the *, +, and ? special characters in
regular expressions.
repeat_sep(pattern, separator) -
Match the given pattern any number of times, separated by the separator.
This converts only the bits that match pattern to Rust values, producing
a Vec. Any parts of the string matched by separator are not converted.
Custom conversion:
... name1:pattern1 ... => expr -
On successfully matching the patterns to the left of =>, evaluate the Rust
expression expr to convert the results to a single Rust value.
Use this to convert input to structs. For instance, suppose your puzzle input contains each elf's name and height:
text
Holly=33
Ivy=7
DouglasFir=1093
and you'd like to turn this into a vector of struct Elf values. The
code you need is:
``` struct Elf { name: String, height: u32, }
let p = parser!(lines( elf:string(alpha+) '=' ht:u32 => Elf { name: elf, height: ht } )); ```
The name elf applies to the pattern string(alpha+) and the name
ht applies to the pattern i32. The bit after the => is
plain old Rust code.
The names are in scope only for the following expr in the same set of matching parentheses or braces.
Alternatives:
{pattern1, pattern2, ...} -
Matches any one of the patterns. First try matching pattern1; if it
matches, stop. If not, try pattern2, and so on. All the patterns must
produce the same type of Rust value.
This is sort of like a Rust match expression.
For example, parser!({"<" => -1, ">" => 1}) either matches <,
returning the value -1, or matches >, returing 1.
Alternatives are handy when you want to convert the input into an enum. For example, my puzzle input for December 23, 2015 was a list of instructions that looked (in part) like this:
text
jie a, +4
tpl a
inc a
jmp +2
hlf a
jmp -7
This can be easily parsed into a vector of beautiful enums, like so:
``` enum Reg { A, B, }
enum Insn { Hlf(Reg), Tpl(Reg), Inc(Reg), Jmp(isize), Jie(Reg, isize), Jio(Reg, isize), }
use Reg::; use Insn::;
let reg = parser!({"a" => A, "b" => B}); let p = parser!(lines({ "hlf " r:reg => Hlf(r), "tpl " r:reg => Tpl(r), "inc " r:reg => Inc(r), "jmp " offset:isize => Jmp(offset), "jie " r:reg ", " offset:isize => Jie(r, offset), "jio " r:reg ", " offset:isize => Jio(r, offset), })); ```
Lines and sections:
line(pattern) - Matches a single line of text that
matches pattern, and the newline at the end of the line.
This is like ^pattern\n in regular expressions,
with two minor differences:
line(pattern) will only ever match exactly
one line of text, even if pattern could match more newlines.
If your input does not end with a newline,
line( can still match the
non-newline-terminated "line" at the end.
line(string(any_char+)) matches a line of text, strips off the newline
character, and returns the rest as a String.
line("") matches a blank line.
lines(pattern) - Matches any number of lines of
text matching pattern. Each line must be terminated by a newline, '\n'.
Equivalent to line(pattern)*.
let p = parser!(lines(repeat_sep(digit, " ")));
assert_eq!(
p.parse("1 2 3\n4 5 6\n").unwrap(),
vec![vec![1, 2, 3], vec![4, 5, 6]],
);
section(pattern) - Matches zero or more nonblank lines,
followed by either a blank line or the end of input. The nonblank lines must match
pattern.
section() consumes the blank line. pattern should not expect to see it.
It's common for an AoC puzzle input to have several lines of data, then
a blank line, and then a different kind of data. You can parse this with
section(p1) section(p2).
section(lines(u64)) matches a section that's a list of numbers, one per line.
sections(pattern) - Matches any number of sections
matching pattern. Equivalent to section(pattern)*
Bringing it all together to parse a complex example:
``` let example = "\ Wiring Diagram #1: a->q->E->z->J D->f->D
Wiring Diagram #2: g->r->f g->B ";
let p = parser!(sections( line("Wiring Diagram #" usize ":") lines(repeatsep(alpha, "->")) )); asserteq!( p.parse(example).unwrap(), vec![ (1, vec![vec!['a', 'q', 'E', 'z', 'J'], vec!['D', 'f', 'D']]), (2, vec![vec!['g', 'r', 'f'], vec!['g', 'B']]), ], ); ```
License: MIT