Basic Parsers

one, one_by: consumes one character if it is equal to c.

let parser = one( c: CharType )

let a_parser = one('a')
let a_parser = 'a'.into_parser()

let a_parser = one_by('a', |value:char, ch:&char| value.to_ascii_lowercase() == *ch );

Output: (Iterator::Item,)

range: consumes one character if it is in the range r.

let parser = range( r: impl std::ops::RangeBounds )

let digit_parser = range( '0'..='9' )
let digit_parser = ('0'..='9').into_parser()

Output: (Iterator::Item,)

str, str_by, slice, slice_by: consumes multiple characters if it is equal to s.

For borrowing-safety, the lifetime of str or slice must be 'static.

To use with other lifetime, you should use string() or vec() instead. Those functions will clone the items in String, Vec.

// must be 'static
let hello_parser = str("hello");
let hello_parser = "hello".into_parser();
let hello_parser = str_by("hello", |value:char, ch:char| value.to_ascii_lowercase() == ch );

let hello_parser = slice(&[104, 101, 108, 108, 111]);
let hello_parser = (&[104, 101, 108, 108, 111]).into_parser();
let hello_parser = slice_by(&[104, 101, 108, 108, 111], |value:i32, ch:&i32| value == *ch );

Output: ()

string, string_by, vec, vec_by: consumes multiple characters if it is equal to s.

This will copy all the characters into String or Vec, so lifetime belongs to the parser itself.

let hello_parser = string("hello".to_string());
let hello_parser = "hello".to_string().into_parser();
let hello_parser = string_by("hello".to_string(), |value:char, ch:char| value.to_ascii_lowercase() == ch );

let hello_parser = vec(vec![104, 101, 108, 108, 111]);
let hello_parser = (vec![104, 101, 108, 108, 111]).into_parser();
let hello_parser = vec_by(vec![104, 101, 108, 108, 111], |value:i32, ch:&i32| value == *ch );

Output: ()

check: check single character with a closure

The closure must be either of: Fn(Iterator::Item) -> Option<NewOutput> or Fn(Iterator::Item) -> bool.

let parser = check( |ch:char| if ch.is_alphabetic() { Some(ch) }else{ None } ); // returns Option<char> -> `(char,)` as output
let parser = check( |ch:char| ch.is_alphabetic() ); // returns bool -> `()` as output

If the closure returns Option<NewOutput>, the output will be (NewOutput,). If the closure returns bool, the output will be ().

any: Match any character.

let parser = any();

Output: (Iterator::Item,)

Dictionary: build Trie from a list of strings

// let mut parser = rp::DictBTree::new();
let mut parser = rp::DictHashMap::new();

parser.insert("hello".chars(), (1,));
parser.insert("hello_world".chars(), (2,));
parser.insert("world".chars(), (3,));

// this will match as long as possible
let res = rp::parse(&parser, "hello_world_abcdefg".chars());
assert_eq!(res.output.unwrap(), (2,));
// 'hello_world' is parsed, so the rest is "_abcdefg"
assert_eq!(res.it.collect::<String>(), "_abcdefg");

// match 'hello' only
let res = rp::parse(&parser, "hello_wo".chars());
assert_eq!(res.output.unwrap(), (1,));

Output: generic type you inserted

This will match as long as possible, regardless of the order of insertion.

There are two types of Dictionary: DictBTree and DictHashMap for Trie implementation. Both of them have their own Pros and Cons (the memory usage and time complexity of searching), so you can choose one of them.

Combinators

seq: sequence of parsers

// 'a', and then 'b'
let ab_parser = rp::seq!('a', 'b', 'c'); // IntoParser for char

let res = rp::parse(&ab_parser, "abcd".chars());
assert_eq!(res.output.unwrap(), ('a', 'b', 'c')); // Output is concatenated
assert_eq!(res.it.collect::<String>(), "d");

Output: ( A0, A1, ..., B0, B1, ..., C0, C1, ... ) where (A0, A1, ...) are the output of the first parser, and (B0, B1, ...), (C0, C1, ...) are the output of the following parsers.

or: or combinator

// 'a' or 'b'
let ab_parser = rp::or!('a', 'b'); // IntoParser for char

// 'a' is matched
let res = rp::parse(&ab_parser, "abcd".chars());
assert_eq!(res.output.unwrap(), ('a',)); // Output of 'a'
assert_eq!(res.it.clone().collect::<String>(), "bcd");

// continue parsing from the rest
// 'a' is not matched, but 'b' is matched
let res = rp::parse(&ab_parser, res.it);
assert_eq!(res.output.unwrap(), ('b',));
assert_eq!(res.it.clone().collect::<String>(), "cd");

// continue parsing from the rest
// 'a' is not matched, 'b' is not matched; failed
let res = rp::parse(&ab_parser, res.it);
assert_eq!(res.output, None);
assert_eq!(res.it.clone().collect::<String>(), "cd");

Output: Output of the all parsers. Note that the output of all parsers must be the same type.

map: map the output of the parser

Parser's Output(Tuple) will be unpacked and passed to the closure. The value returned from the closure will be new Output.

// map the output
// <Output of 'a'> -> i32
let int_parser = 'a'.map(|ch| -> i32 { ch as i32 - 'a' as i32 }); // IntoParser for char

let res = rp::parse(&int_parser, "abcd".chars());
assert_eq!(res.output.unwrap(), (0,));
assert_eq!(res.it.collect::<String>(), "bcd");

Output: (T,) where T is return type of the closure. The value v returned from the closure will be wrapped into (v,).

repeat: repeat the parser multiple times

// repeat 'a' 3 to 5 times
let multiple_a_parser = 'a'.repeat(3..=5); // IntoParser for char
let res = rp::parse(&multiple_a_parser, "aaaabcd".chars());

// four 'a' is parsed
assert_eq!(res.output.unwrap(), (vec!['a', 'a', 'a', 'a',],));
assert_eq!(res.it.collect::<String>(), "bcd");

Output:

• if Output of the repeated parser is (), then Output is ()
• if Output of the repeated parser is (T,), then Output is Vec<T>
• otherwise, Vec< Output of Self >

optional, optional_or, or_else: success whether the pattern is matched or not

let a_optional_parser = 'a'.optional(); // (Option<char>,)

let res = rp::parse(&a_optional_parser, "abcd".chars()); // success
assert_eq!(res.output.unwrap(), (Some('a'),));

let res = rp::parse(&a_optional_parser, "bcd".chars()); // success, but 'a' is not matched
assert_eq!(res.output.unwrap(), (None,));

// if 'a' failed, return 'x'
let a_optional_or = 'a'.optional_or(('x',)); // (char,)

let res = rp::parse(&a_optional_or, "bcd".chars());
assert_eq!(res.output.unwrap(), ('x',));

// if 'a' failed, evaluate the closure
let a_or_else = 'a'.or_else( || 'x' ); // (char,)
assert_eq!(res.output.unwrap(), ('x',));

Output for optional:

• if Output of the origin parser is (T0,), (Option<T0>,)
• otherwise, ( Option<Output of Self>, )

Output for optional_or, or_else:

• <Output of Self>.

Note

• The passed value's type to optional_or and or_else must match with the Output of Self
• For single-value-output ( which's output is (T,) ), passing either T or (T,) is permitted.

not: match for Pattern1 to success and Pattern2 to fail

// all digit but not 4
let digit_parser_except_4 = ('0'..='9').not('4');

let res = rp::parse(&digit_parser_except_4, "3".chars());
assert_eq!(res.output.unwrap(), ('3',));

let res = rp::parse(&digit_parser_except_4, "4".chars());
assert_eq!(res.output, None);

Output: Output of Self

reduce_left: reduce the output of the parser

With given input string self rhs rhs rhs rhs ... and the reducer f, the output will be calculated as f( f( f(self,rhs), rhs ), rhs ), ...

Note

• The signature of the reducer must be Fn(A0, A1, A2, ..., B0, B1, B2, ...) -> ( A0, A1, A2 ... ). Where (A0, A1, A2, ...) are the output of the first parser, and (B0, B1, B2, ...) are the output of the following parser.

• For single-value-output ( which's output is (T,) ), returning either T or (T,) is permitted.

let digit_parser = ('0'..='9').into_parser().map(|val: char| -> i32 { val as i32 - '0' as i32 });
let reduced_left = digit_parser.reduce_left(digit_parser, |lhs, rhs| lhs * 10 + rhs);
let res = rp::parse( &reduced_left, "123456abcd".chars() );
assert_eq!(res.output.unwrap(), (123456,));
assert_eq!(res.it.collect::<String>(), "abcd");

Output: Output of Self

reduce_right: reduce the output of the parser

With given input string lhs lhs lhs lhs ... self and the reducer f, the output will be calculated as f(lhs, f(lhs, f(lhs, f( ... f(lhs,self)))

Note

• The signature of the reducer must be Fn(A0, A1, A2, ..., B0, B1, B2, ...) -> ( B0, B1, B2 ... ). Where (A0, A1, A2, ...) are the output of the first parser, and (B0, B1, B2, ...) are the output of the following parser.

• For single-value-output ( which's output is (T,) ), returning either T or (T,) is permitted.

let digit_parser =
    ('0'..='9').into_parser().map(|val: char| -> i32 { val as i32 - '0' as i32 });
let alphabet_parser =
    ('a'..='z').into_parser().map(|val: char| -> i32 { val as i32 - 'a' as i32 });
let reduced_right =
    alphabet_parser.reduce_right(digit_parser, |lhs: i32, rhs: i32| -> i32 { rhs * 10 + lhs });

let res = rp::parse(&reduced_right, "123456dcba".chars());
assert_eq!(res.output.unwrap(), (3654321,));
assert_eq!(res.it.collect::<String>(), "cba");

Output: Output of Self

reduce_with: reduce the output of the parser with initial value

With given input string self self self ... and the reducer f, the output will be calculated as f( f( f(init,self), self), self), ...

The signature of the reducer must be Fn(Init, A0, A1, A2, ...) -> Init. Where (A0, A1, A2, ...) are the output of Self.

Output: Init

let digit_parser =
    ('0'..='9').into_parser().map(|val: char| -> i32 { val as i32 - '0' as i32 });
let number_parser =
    digit_parser.reduce_with(0, |acc, rhs| acc * 10 + rhs);

let res = rp::parse(&number_parser, "123456abc".chars());
assert_eq!(res.output.unwrap(), (123456,));
assert_eq!(res.it.collect::<String>(), "abc");

reduce_right_with: reduce the output of the parser with initial value

With given input string self self self ... and the reducer f, the output will be calculated as f(self, f(self, f(self, f( ... f(self,init)))

The signature of the reducer must be Fn(A0, A1, A2, ..., Init) -> Init. Where (A0, A1, A2, ...) are the output of Self.

Output: Init

Example

let digit_parser =
    ('0'..='9').into_parser().map(|val: char| -> i32 { val as i32 - '0' as i32 });
let number_rev_parser =
    digit_parser.reduce_right_with(0, |lhs, acc| acc * 10 + lhs);

let res = rp::parse(&number_rev_parser, "123456abc".chars());
assert_eq!(res.output.unwrap(), (654321,));
assert_eq!(res.it.collect::<String>(), "abc");

Others

Trivial, but useful parsers

constant: This parser will always succeed, and return the constant value

let parser = rp::constant( (1, 2, 3) );

Output: the Tuple value you provided

end: success if it reached to the end of input

let end_parser = rp::end();

Output: ()

fail: This parser will always fail

let parser = rp::fail();

Output: ()

void: ignore the output of the parser

Force the output to be (). It internally calls match_pattern(...) instead of parse(...). This is useful when you only want to check if the pattern is matched or not. For more information, see match_pattern(...) above.

let expensive_parser = 'a'.map(|_| -> i32 {
    // some expensive operations for data extracting...
    panic!("This should not be called");
});
let expensive_parser = expensive_parser.void();

// ignore the output of parser
// this internally calls 'match_pattern(...)' instead of 'parse(...)'
let res = rp::parse(&expensive_parser, "abcd".chars());
assert_eq!(res.output.unwrap(), ());
assert_eq!(res.it.collect::<String>(), "bcd");

Output: ()

output: Change Parser's Output to (output,)

let digit_parser = ('0'..='9').output(2024);

let res = rp::parse(&digit_parser, "123456hello_world".chars());
assert_eq!(res.output.unwrap(), (2024,));
assert_eq!(res.it.collect::<String>(), "23456hello_world");

Output: (T,) where T is the type of the value you provided.

string, vec: captures the matched range into String or Vec<T>

Note

string can be only used for std::str::Chars, and vec can be only used for ExactSizeIterator.

let digits_parser = ('0'..='9').repeat(0..).string();

let res = rp::parse(&digits_parser, "123456hello_world".chars());
assert_eq!(res.output.unwrap(), ("123456".to_string(),));
assert_eq!(res.it.collect::<String>(), "hello_world");

Output: (String,) or (Vec<Iterator::Item>,)

not_consume: check if the pattern is matched or not, without consuming the input

let digit_parser = ('0'..='9').not_consume();

let res = rp::parse(&digit_parser, "12345".chars());
assert_eq!(res.output.unwrap(), ('1',));
assert_eq!(res.it.collect::<String>(), "12345"); // iterator is not consumed

Output: Output of Self