This combinator repeatedly parses a given parser n or more times, collecting the results into a list.

Parses a given parser, p, repeatedly until it fails. If p failed having consumed input, this combinator fails. Otherwise when p fails without consuming input, this combinator will return all of the results, x1 through xm (with m >= n), in a list: [x1, .., xm]. If p was not successful at least n times, this combinator fails.

Examples

>>> let p = manyN 2 (string "ab")
>>> parse @String p ""
Failure ..
>>> parse @String p "ab"
Failure ..
>>> parse @String p "abababab"
Success ["ab", "ab", "ab", "ab"]
>>> parse @String p "aba"
Failure ..

Notes

• many p == many 0 p and some p == many 1 p.

Since: 0.1.0.0

This combinator repeatedly parses a given parser zero or more times, ignoring the results.

Parses a given parser, p, repeatedly until it fails. If p failed having consumed input, this combinator fails. Otherwise when p fails without consuming input, this combinator will succeed.

Examples

>>> let p = skipMany (string "ab")
>>> parse @String p ""
Success ()
>>> parse @String p "ab"
Success ()
>>> parse @String p "abababab"
Success ()
>>> parse @String p "aba"
Failure ..

Since: 0.1.0.0

This combinator repeatedly parses a given parser one or more times, ignoring the results.

Parses a given parser, p, repeatedly until it fails. If p failed having consumed input, this combinator fails. Otherwise when p fails without consuming input, this combinator will succeed. The parser p must succeed at least once.

Examples

>>> let p = skipSome (string "ab")
>>> parse @String p ""
Failure ..
>>> parse @String p "ab"
Success ()
>>> parse @String p "abababab"
Success ()
>>> parse @String p "aba"
Failure ..

Since: 0.1.0.0

This combinator repeatedly parses a given parser n or more times, ignoring the results.

Parses a given parser, p, repeatedly until it fails. If p failed having consumed input, this combinator fails. Otherwise when p fails without consuming input, this combinator will succeed. The parser p must succeed at least n times.

Examples

>>> let p = skipManyN 2 (string "ab")
>>> parse @String p ""
Failure ..
>>> parse @String p "ab"
Failure ..
>>> parse @String p "abababab"
Success ()
>>> parse @String p "aba"
Failure ..

Since: 0.1.0.0

This combinator repeatedly parses a given parser zero or more times, returning how many times it succeeded.

Parses a given parser, p, repeatedly until it fails. If p failed having consumed input, this combinator fails. Otherwise when p fails without consuming input, this combinator will succeed. The number of times p succeeded is returned as the result.

Examples

>>> let p = count (string "ab")
>>> parse @String p ""
Success 0
>>> parse @String p "ab"
Success 1
>>> parse @String p "abababab"
Success 4
>>> parse @String p "aba"
Failure ..

Since: 0.1.0.0

This combinator repeatedly parses a given parser one or more times, returning how many times it succeeded.

Parses a given parser, p, repeatedly until it fails. If p failed having consumed input, this combinator fails. Otherwise when p fails without consuming input, this combinator will succeed. The number of times p succeeded is returned as the result.

The parser p must succeed at least once.

Examples

>>> let p = count1 (string "ab")
>>> parse @String p ""
Failure ..
>>> parse @String p "ab"
Success 1
>>> parse @String p "abababab"
Success 4
>>> parse @String p "aba"
Failure ..

Since: 0.1.0.0

This combinator repeatedly parses a given parser zero or more times, until the end parser succeeds, collecting the results into a list.

First tries to parse end, if it fails without consuming input, then parses p, which must succeed. This repeats until end succeeds. When end does succeed, this combinator will return all of the results generated by p, x1 through xn (with n >= 0), in a list: [x1, .., xn]. If end could be parsed immediately, the empty list is returned.

Examples

>>> let comment = string "--" *> manyUntil item endOfLine
>>> parse @String p "--hello world"
Failure ..
>>> parse @String p "--hello world\n"
Success ['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']
>>> parse @String p "--\n"
Success Nil

Since: 0.1.0.0

This combinator repeatedly parses a given parser one or more times, until the end parser succeeds, collecting the results into a list.

First ensures that trying to parse end fails, then tries to parse p. If it succeeds then it will repeatedly: try to parse end, if it fails without consuming input, then parses p, which must succeed. When end does succeed, this combinator will return all of the results generated by p, x1 through xn (with n >= 1), in a list: [x1, .., xn].

The parser p must succeed at least once before end succeeds.

Examples

>>> let comment = string "--" *> someUntil item endOfLine
>>> parse @String p "--hello world"
Failure ..
>>> parse @String p "--hello world\n"
Success ['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']
>>> parse @String p "--\n"
Failure ..
>>> parse @String p "--a\n"
Success ['a']

Since: 0.1.0.0

This combinator repeatedly parses a given parser zero or more times, until the end parser succeeds, discarding any results from p.

Behaves like manyTill, except the results of parsing p are ignored.

First tries to parse end, if it fails without consuming input, then parses p, which must succeed. This repeats until end succeeds. When end does succeed (even of the first try), this combinator will discard any results generated by p.

This combinator repeatedly parses a given parser one or more times, until the end parser succeeds, discarding any results from p, and returns unit.

Behaves like someTill, except the results of parsing p are ignored.

First ensures that trying to parse end fails, then tries to parse p. If it succeeds then it will repeatedly: try to parse end, if it fails without consuming input, then parses p, which must succeed. When end does succeed, this combinator will discard any results generated by p, returning unit.

The parser p must succeed at least once before end succeeds.

This combinator tries to parse p, wrapping its result in a Just if it succeeds, or returns Nothing if it fails.

Tries to parse p. If p succeeded, producing x, then Just x is returned. Otherwise, if p failed without consuming input, then Nothing is returned instead.

Examples

>>> let p = option (string "abc")
>>> parse @String p ""
Success Nothing
>>> parse @String p "abc"
Success (Just "abc")
>>> parse @String p "ab"
Failure ..

Since: 0.1.0.0

This combinator will parse p if possible, otherwise will do nothing.

Tries to parse p. If p succeeds, or fails without consuming input then this combinator is successful. Otherwise, if p failed having consumed input, this combinator fails.

Examples

>>> let p = optional (string "abc")
>>> parse @String p ""
Success ()
>>> parse @String p "abc"
Success ()
>>> parse @String p "ab"
Failure ..

Since: 0.1.0.0

This combinator will parse p if possible, otherwise will do nothing.

Tries to parse p. If p succeeds, or fails without consuming input then this combinator is successful and returns x. Otherwise, if p failed having consumed input, this combinator fails.

Examples

>>> let p = optionalAs 7 (string "abc")
>>> parse @String p ""
Success 7
>>> parse @String p "abc"
Success 7
>>> parse @String p "ab"
Failure ..

Since: 0.1.0.0

This combinator can eliminate a Maybe from the result of the parser p.

First parse p, if it succeeds returning Just x, then return x. However, if p fails, or returned Nothing, then this combinator fails.

Examples

decide (option p) = p

This combinator parses q depending only if p returns a Nothing.

First parses p. If p returned Just x, then x is returned. Otherwise, if p returned Nothing then q is parsed, producing y, and y is returned. If p or q fails, the combinator fails.

Examples

Since: 0.1.0.0

This combinator parses zero or more occurrences of p, separated by sep.

Behaves just like sepBy1, except does not require an initial p, returning the empty list instead.

Examples

>>> ...
>>> let args = sepBy int (string ", ")
>>> parse @String args "7, 3, 2"
Success [7, 3, 2]
>>> parse @String args ""
Success []
>>> parse @String args "1"
Success [1]
>>> parse @String args "1, 2, "
Failure ..

Since: 0.1.0.0

This combinator parses one or more occurrences of p, separated by sep.

First parses a p. Then parses sep followed by p until there are no more seps. The results of the p's, x1 through xn, are returned as [x1, .., xn]. If p or sep fails having consumed input, the whole parser fails.

Requires at least one p to have been parsed.

Examples

>>> ...
>>> let args = sepBy1 int (string ", ")
>>> parse @String args "7, 3, 2"
Success [7, 3, 2]
>>> parse @String args ""
Failure ..
>>> parse @String args "1"
Success [1]
>>> parse @String args "1, 2, "
Failure ..

Since: 0.1.0.0

This combinator parses zero or more occurrences of p, separated and optionally ended by sep.

Behaves just like sepEndBy1, except does not require an initial p, returning the empty list instead.

Examples

>>> ...
>>> let args = sepEndBy int (string ";\n")
>>> parse @String args "7;\n3;\n2"
Success [7, 3, 2]
>>> parse @String args ""
Success Nil
>>> parse @String args "1"
Success [1]
>>> parse @String args "1;\n2;\n"
Success [1, 2]

Since: 0.1.0.0

This combinator parses one or more occurrences of p, separated and optionally ended by sep.

First parses a p. Then parses sep followed by p until there are no more: if a final sep exists, this is parsed. The results of the p's, x1 through xn, are returned as [x1, .., xn]. If p or sep fails having consumed input, the whole parser fails.

Requires at least one p to have been parsed.

Examples

>>> ...
>>> let args = sepEndBy1 int (string ";\n")
>>> parse @String args "7;\n3;\n2"
Success [7, 3, 2]
>>> parse @String args ""
Failure ..
>>> parse @String args "1"
Success [1]
>>> parse @String args "1;\n2;\n"
Success [1, 2]

Since: 0.1.0.0

This combinator parses zero or more occurrences of p, separated and ended by sep.

Behaves just like endBy1, except does not require an initial p and sep, returning the empty list instead.

Examples

>>> ...
>>> let args = endBy int (string ";\n")
>>> parse @String args "7;\n3;\n2"
Failure ..
>>> parse @String args ""
Success Nil
>>> parse @String args "1;\n"
Success [1]
>>> parse @String args "1;\n2;\n"
Success [1, 2]

Since: 0.1.0.0

This combinator parses one or more occurrences of p, separated and ended by sep.

Parses p followed by sep one or more times. The results of the p's, x1 through xn, are returned as [x1, .., xn]. If p or sep fails having consumed input, the whole parser fails.

Requires at least one p to have been parsed.

Examples

>>> ...
>>> let args = endBy1 int (string ";\n")
>>> parse @String args "7;\n3;\n2"
Failure ..
>>> parse @String args ""
Failure ..
>>> parse @String args "1;\n"
Success [1]
>>> parse @String args "1;\n2;\n"
Success [1, 2]

Since: 0.1.0.0

This combinator tries to parse each of the parsers ps in order, until one of them succeeds.

Finds the first parser in ps which succeeds, returning its result. If Nothing of the parsers succeed, then this combinator fails. If a parser fails having consumed input, this combinator fails immediately.

Examples

>>> let p = choice [string "abc", string "ab", string "bc", string "d"]
>>> parse @String p "abc"
Success "abc"
>>> parse @String p "ab"
Failure ..
>>> parse @String p "bc"
Success "bc"
>>> parse @String p "x"
Failure ..

Since: 0.1.0.0

Evaluate each monadic action in the structure from left to right, and collect the results. For a version that ignores the results see sequence_.

Examples

>>> sequence $ Right [1,2,3,4]
[Right 1,Right 2,Right 3,Right 4]

>>> sequence $ [Right 1,Right 2,Right 3,Right 4]
Right [1,2,3,4]

>>> sequence $ Left [1,2,3,4]
Left [1,2,3,4]

>>> sequence $ [Left 0, Right 1,Right 2,Right 3,Right 4]
Left 0

Map each element of a structure to an action, evaluate these actions from left to right, and collect the results. For a version that ignores the results see traverse_.

Examples

>>> traverse Just [1,2,3,4]
Just [1,2,3,4]

>>> traverse id [Right 1, Right 2, Right 3, Right 4]
Right [1,2,3,4]

>>> traverse (const Nothing) [1,2,3,4]
Nothing

>>> traverse (\x -> if odd x then Just x else Nothing)  [1,2,3,4]
Nothing

>>> traverse id [Right 1, Right 2, Right 3, Right 4, Left 0]
Left 0

This combinator will parse each of ps in order, discarding the results.

Given the parsers ps, consisting of p1 through pn, parses each in order. If they all succeed, this combinator succeeds. If any of the parsers fail, then the whole combinator fails.

Examples

>>> let p = skip [char'a', item, char 'c']
>>> parse @String p "abc"
Success ()
>>> parse @String p "ab"
Failure ..

Since: 0.1.0.0

This combinator parses exactly n occurrences of p, returning these n results in a list.

Parses p repeatedly up to n times. If p fails before n is reached, then this combinator fails. It is not required for p to fail after the nth parse. The results produced by p, x1 through xn, are returned as [x1, .., xn].

Examples

>>> let p = exactly 3 item
>>> parse @String p "ab"
Failure ..
>>> parse @String p "abc"
Success ['a', 'b', 'c']
>>> parse @String p "abcd"
Success ['a', 'b', 'c']

Since: 0.1.0.0

This combinator parses between min and max occurrences of p, returning these n results in a list.

Parses p repeatedly a minimum of min times and up to max times both inclusive. If p fails before min is reached, then this combinator fails. It is not required for p to fail after the max^th^ parse. The results produced by p, xmin through xmax, are returned as [xmin, .., xmax].

Examples

>>> let p = range 3 5 item
>>> parse @String p "ab"
Failure ..
>>> parse @String p "abc"
Success ['a', 'b', 'c']
>>> parse @String p "abcd"
Success ['a', 'b', 'c', 'd']
>>> parse @String p "abcde"
Success ['a', 'b', 'c', 'd', 'e']
>>> parse @String p "abcdef"
Success ['a', 'b', 'c', 'd', 'e']

Since: 0.1.0.0

This combinator parses between min and max occurrences of p but ignoring the results.

Parses p repeatedly a minimum of min times and up to max times both inclusive. If p fails before min is reached, then this combinator fails. It is not required for p to fail after the maxth parse. The results are discarded and () is returned instead.

Examples

>>> let p = range_ 3 5 item
>>> parse @String p "ab"
Failure ..
>>> parse @String p "abc"
Success ()
>>> parse @String p "abcd"
Success ()
>>> parse @String p "abcde"
Success ()
>>> parse @String p "abcdef"
Success ()

Since: 0.1.0.0

This combinator parses between min and max occurrences of p, returning the number of successes.

Parses p repeatedly a minimum of min times and up to max times both inclusive. If p fails before min is reached, then this combinator fails. It is not required for p to fail after the maxth parse. The results are discarded and the number of successful parses of p, n, is returned instead, such that min <= n <= max.

Examples

>>> let p = count 3 5 item
>>> parse @String p "ab"
Failure ..
>>> parse @String p "abc"
Success 3
>>> parse @String p "abcd"
Success 4
>>> parse @String p "abcde"
Success 5
>>> parse @String p "abcdef"
Success 5

Since: 0.1.0.0

This combinator parses one of thenP or elseP depending on the result of parsing condP.

This is a lifted if-statement. First, parse condP: if it is successful and returns True, then parse thenP; else, if it returned False, parse elseP; or, if condP failed then fail. If either of thenP or elseP fail, then this combinator also fails.

Most useful in conjunction with Registers, as this allows for decisions to be made based on state.

Examples

>>> ifP (pure True) p _ == p
>>> ifP (pure False) _ p == p

Since: 0.1.0.0

This combinator conditionally parses thenP depending on the result of parsing condP.

This is a lifted if-statement. First, parse condP: if it is successful and returns True, then parse thenP; else, if it returned False do nothing; or, if condP failed then fail. If thenP fails, then this combinator also fails.

Most useful in conjunction with Registers, as this allows for decisions to be made based on state.

Examples

>>> when (pure True) p == p
>>> when (pure False) _ == unit

Since: 0.1.0.0

This combinator verfies that the given parser returns True, or else fails.

First, parse p; if it succeeds then, so long at returns True, this guard p succeeds. Otherwise, if p either fails, or returns False, guard p will fail.

Examples

>>> guard (pure True) == unit
>>> guard (pure False) == empty
>>> when (not <$> p) empty == guard p

Since: 0.1.0.0

This combinator repeatedly parses p so long as it returns True.

This is a lifted while-loop. First, parse p: if it is successful and returns True, then repeat; else if it returned False stop; or, if it failed then this combinator fails.

Most useful in conjunction with Registers, as this allows for decisions to be made based on state. In particular, this can be used to define the forP combinator.

Since: 0.1.0.0