@spec ascii_char(t(), [range()]) :: t()

Defines a single ASCII codepoint in the given ranges.

ranges is a list containing one of:

• a min..max range expressing supported codepoints
• a codepoint integer expressing a supported codepoint
• {:not, min..max} expressing not supported codepoints
• {:not, codepoint} expressing a not supported codepoint

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :digit_and_lowercase,
            empty()
            |> ascii_char([?0..?9])
            |> ascii_char([?a..?z])
end

MyParser.digit_and_lowercase("1a")
#=> {:ok, [?1, ?a], "", %{}, {1, 0}, 2}

MyParser.digit_and_lowercase("a1")
#=> {:error, "expected ASCII character in the range '0' to '9', followed by ASCII character in the range 'a' to 'z'", "a1", %{}, {1, 0}, 0}

@spec ascii_string(t(), [range()], pos_integer() | [min_and_max()]) :: t()

Defines an ASCII string combinator with an exact length or min and max length.

The ranges specify the allowed characters in the ASCII string. See ascii_char/2 for more information.

If you want a string of unknown size, use ascii_string(ranges, min: 1). If you want a literal string, use string/2.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :two_lowercase_letters, ascii_string([?a..?z], 2)
end

MyParser.two_lowercase_letters("abc")
#=> {:ok, ["ab"], "c", %{}, {1, 0}, 2}

@spec byte_offset(t(), t()) :: t()

Puts the result of the given combinator as the first element of a tuple with the byte_offset as second element.

byte_offset is a non-negative integer.

@spec choice(t(), [t(), ...], opts()) :: t()

Chooses one of the given combinators.

Expects at least two choices.

Beware! Char combinators

Note both utf8_char/2 and ascii_char/2 allow multiple ranges to be given. Therefore, instead this:

choice([
  ascii_char([?a..?z]),
  ascii_char([?A..?Z]),
])

One should simply prefer:

ascii_char([?a..?z, ?A..?Z])

As the latter is compiled more efficiently by NimbleParsec.

Beware! Always successful combinators

If a combinator that always succeeds is given as a choice, that choice will always succeed which may lead to unused function warnings since any further choice won't ever be attempted. For example, because repeat/2 always succeeds, the string/2 combinator below it won't ever run:

choice([
  repeat(ascii_char([?0..?9])),
  string("OK")
])

Instead of repeat/2, you may want to use times/3 with the flags :min and :max.

Beware! Overlapping choices

In case choices overlap, there is no guarantee which error will be the one effectively returned. For example, imagine this choice:

choice([
  string("<abc>foo</abc>"),
  string("<abc>")
]

ß Since both choices can be activated for an input starting with "abc", NimbleParsec guarantees it will return the error from one of them, but not which.

@spec concat(t(), t()) :: t()

Concatenates two combinators.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :digit_upper_lower_plus,
            concat(
              concat(ascii_char([?0..?9]), ascii_char([?A..?Z])),
              concat(ascii_char([?a..?z]), ascii_char([?+..?+]))
            )
end

MyParser.digit_upper_lower_plus("1Az+")
#=> {:ok, [?1, ?A, ?z, ?+], "", %{}, {1, 0}, 4}

@spec debug(t(), t()) :: t()

Inspects the combinator state given to to_debug with the given opts.

Defines a combinator with the given name and opts.

It is similar to defparsec/3 except it does not define an entry-point parsing function, just the combinator function to be used with parsec/2.

Defines a combinator with the given name and opts.

It is similar to defparsecp/3 except it does not define an entry-point parsing function, just the combinator function to be used with parsec/2.

Defines a parser (and a combinator) with the given name and opts.

The parser is a function that receives two arguments, the binary to be parsed and a set of options. You can consult the documentation of the generated parser function for more information.

This function will also define a combinator that can be used as parsec(name) when building other parsers. See parsec/2 for more information on invoking compiled combinators.

Beware!

defparsec/3 is executed during compilation. This means you can't invoke a function defined in the same module. The following will error because the date function has not yet been defined:

defmodule MyParser do
  import NimbleParsec

  def date do
    integer(4)
    |> ignore(string("-"))
    |> integer(2)
    |> ignore(string("-"))
    |> integer(2)
  end

  defparsec :date, date()
end

This can be solved in different ways. You may simply compose a long parser using variables. For example:

defmodule MyParser do
  import NimbleParsec

  date =
    integer(4)
    |> ignore(string("-"))
    |> integer(2)
    |> ignore(string("-"))
    |> integer(2)

  defparsec :date, date
end

Alternatively, you may define a Helpers module with many convenience combinators, and then invoke them in your parser module:

defmodule MyParser.Helpers do
  import NimbleParsec

  def date do
    integer(4)
    |> ignore(string("-"))
    |> integer(2)
    |> ignore(string("-"))
    |> integer(2)
  end
end

defmodule MyParser do
  import NimbleParsec
  import MyParser.Helpers

  defparsec :date, date()
end

The approach of using helper modules is the favorite way of composing parsers in NimbleParsec.

Options

• :inline - when true, inlines clauses that work as redirection for other clauses. Settings this may improve runtime performance at the cost of increased compilation time and bytecode size

• :debug - when true, writes generated clauses to :stderr for debugging

• :export_combinator - make the underlying combinator function public so it can be used as part of parsec/1 from other modules

• :export_metadata - export metadata necessary to use this parser combinator to generate inputs

Defines a private parser (and a combinator) with the given name and opts.

The same as defparsec/3 but the parsing function is private.

@spec duplicate(t(), t(), non_neg_integer()) :: t()

Duplicates the combinator to_duplicate n times.

@spec empty() :: t()

Returns an empty combinator.

An empty combinator cannot be compiled on its own.

@spec eos(t()) :: t()

Defines an end of string combinator.

The end of string does not produce a token and can be parsed multiple times. This function is useful to avoid having to check for an empty remainder after a successful parse.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :letter_pairs, utf8_string([], 2) |> repeat() |> eos()
end

MyParser.letter_pairs("hi")
#=> {:ok, ["hi"], "", %{}, {1, 0}, 2}

MyParser.letter_pairs("hello")
#=> {:error, "expected end of string", "o", %{}, {1, 0}, 4}

@spec eventually(t(), t()) :: t()

Marks the given combinator should appear eventually.

Any other data before the combinator appears is discarded. If the combinator never appears, then it is an error.

Note: this can be potentially a very expensive operation as it executes the given combinator byte by byte until finding an eventual match or ultimately failing. For example, if you are looking for an integer, it is preferrable to discard everything that is not an integer

ignore(ascii_string([not: ?0..?9]))

rather than eventually look for an integer

eventually(ascii_string([?0..?9]))

Examples

defmodule MyParser do
  import NimbleParsec

  hour = integer(min: 1, max: 2)
  defparsec :extract_hour, eventually(hour)
end

MyParser.extract_hour("let's meet at 12?")
#=> {:ok, [12], "?", %{}, {1, 0}, 16}

Generate a random binary from the given parsec.

Let's see an example:

import NimbleParsec
generate(choice([string("foo"), string("bar")]))

The command above will return either "foo" or "bar". generate/1 is often used with pre-defined parsecs. In this case, the :export_metadata flag must be set:

defmodule SomeModule do
  import NimbleParsec
  defparsec :parse,
            choice([string("foo"), string("bar")]),
            export_metadata: true
end

# Reference the parsec and generate from it
NimbleParsec.parsec({SomeModule, :parse})
|> NimbleParsec.generate()
|> IO.puts()

generate/1 can often run forever for recursive algorithms. Read the notes below and make use of the gen_weight and gen_times option to certain parsecs to control the recursion depth.

Notes

Overall, there is no guarantee over the generated output, except that it will generate a binary that is parseable by the parsec itself, but even this guarantee may be broken by parsers that have custom validations. Keep in mind the following:

• generate/1 is not compatible with NimbleParsec's dumped via mix nimble_parsec.compile;

• parsec/2 requires the referenced parsec to set export_metadata: true on its definition;

• choice/2 will be generated evenly. You can pass :gen_weights as a list of positive integer weights to balance your choices. This is particularly important for recursive algorithms;

• repeat/2 and repeat_while/3 will repeat between 0 and 3 times unless a :gen_times option is given to these operations. times/3 without a :max will also additionally repeat between 0 and 3 times unless :gen_times is given. The :gen_times option can either be an integer as the number of times to repeat or a range where a random value in the range will be picked;

• eventually/2 always generates the eventually parsec immediately;

• lookahead/2 and lookahead_not/2 are simply discarded;

• Validations done in any of the traverse definitions are not taken into account by the generator. Therefore, if a parsec does validations, the generator may generate binaries invalid to said parsec;

@spec ignore(t(), t()) :: t()

Ignores the output of combinator given in to_ignore.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :ignorable, string("T") |> ignore() |> integer(2)
end

MyParser.ignorable("T12")
#=> {:ok, [12], "", %{}, {1, 0}, 2}

@spec integer(t(), pos_integer() | [min_and_max()]) :: t()

Defines an integer combinator with of exact length or min and max length.

If you want an integer of unknown size, use integer(min: 1).

This combinator does not parse the sign and is always on base 10.

Examples

With exact length:

defmodule MyParser do
  import NimbleParsec

  defparsec :two_digits_integer, integer(2)
end

MyParser.two_digits_integer("123")
#=> {:ok, [12], "3", %{}, {1, 0}, 2}

MyParser.two_digits_integer("1a3")
#=> {:error, "expected ASCII character in the range '0' to '9', followed by ASCII character in the range '0' to '9'", "1a3", %{}, {1, 0}, 0}

With min and max:

defmodule MyParser do
  import NimbleParsec

  defparsec :two_digits_integer, integer(min: 2, max: 4)
end

MyParser.two_digits_integer("123")
#=> {:ok, [123], "", %{}, {1, 0}, 2}

MyParser.two_digits_integer("1a3")
#=> {:error, "expected ASCII character in the range '0' to '9', followed by ASCII character in the range '0' to '9'", "1a3", %{}, {1, 0}, 0}

If the size of the integer has a min and max close to each other, such as from 2 to 4 or from 1 to 2, using choice may emit more efficient code:

choice([integer(4), integer(3), integer(2)])

Note you should start from bigger to smaller.

@spec label(t(), t(), String.t()) :: t()

Adds a label to the combinator to be used in error reports.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :digit_and_lowercase,
            empty()
            |> ascii_char([?0..?9])
            |> ascii_char([?a..?z])
            |> label("digit followed by lowercase letter")
end

MyParser.digit_and_lowercase("1a")
#=> {:ok, [?1, ?a], "", %{}, {1, 0}, 2}

MyParser.digit_and_lowercase("a1")
#=> {:error, "expected a digit followed by lowercase letter", "a1", %{}, {1, 0}, 0}

@spec line(t(), t()) :: t()

Puts the result of the given combinator as the first element of a tuple with the line as second element.

line is a tuple where the first element is the current line and the second element is the byte offset immediately after the newline.

@spec lookahead(t(), t()) :: t()

Checks if a combinator is ahead.

If it succeeds, it continues as usual, otherwise it aborts the closest choice/2, repeat/2, etc. If there is no closest operation to abort, then it errors.

Note a lookahead never changes the accumulated output nor the context.

Examples

For example, imagine you want to parse a language that has the keywords "if" and "while" and identifiers made of any letters or number, where keywords and identifiers can be separated by a single white space:

defmodule IfWhileLang do
  import NimbleParsec

  keyword =
    choice([
      string("if") |> replace(:if),
      string("while") |> replace(:while)
    ])

  identifier =
    ascii_string([?a..?z, ?A..?Z, ?0..?9], min: 1)

  defparsec :expr, repeat(choice([keyword, identifier]) |> optional(string(" ")))
end

The issue with the implementation above is that the following will parse:

IfWhileLang.expr("iffy")
{:ok, [:if, "fy"], "", %{}, {1, 0}, 4}

However, "iffy" should be treated as a full identifier. We could solve this by inverting the order of keyword and identifier in :expr but that means "if" itself will be considered an identifier and not a keyword. To solve this, we need lookaheads.

One option is to check that after the keyword we either have an empty string OR the end of the string:

keyword =
  choice([
    string("if") |> replace(:if),
    string("while") |> replace(:while)
  ])
  |> lookahead(choice([string(" "), eos()]))

However, in this case, a negative lookahead may be clearer, and we can assert that we don't have any identifier character after the keyword:

keyword =
  choice([
    string("if") |> replace(:if),
    string("while") |> replace(:while)
  ])
  |> lookahead_not(ascii_char([?a..?z, ?A..?Z, ?0..?9]))

Now we get the desired result back:

IfWhileLang.expr("iffy")
#=> {:ok, ["iffy"], "", %{}, {1, 0}, 4}

IfWhileLang.expr("if fy")
#=> {:ok, [:if, " ", "fy"], "", %{}, {1, 0}, 5}

@spec lookahead_not(t(), t()) :: t()

Checks if a combinator is not ahead.

If it succeeds, it aborts the closest choice/2, repeat/2, etc. Otherwise it continues as usual. If there is no closest operation to abort, then it errors.

Note a lookahead never changes the accumulated output nor the context.

For an example, see lookahead/2.

@spec map(t(), t(), call()) :: t()

Maps over the combinator results with the remote or local function in call.

call is either a {module, function, args} representing a remote call, a {function, args} representing a local call or an atom function representing {function, []}.

Each parser result will be invoked individually for the call. Each result be prepended to the given args. The args will be injected at the compile site and therefore must be escapable via Macro.escape/1.

See post_traverse/3 for a low level version of this function.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :letters_to_string_chars,
            ascii_char([?a..?z])
            |> ascii_char([?a..?z])
            |> ascii_char([?a..?z])
            |> map({Integer, :to_string, []})
end

MyParser.letters_to_string_chars("abc")
#=> {:ok, ["97", "98", "99"], "", %{}, {1, 0}, 3}

@spec optional(t(), t()) :: t()

Marks the given combinator as optional.

It is equivalent to choice([optional, empty()]).

@spec parsec(t(), name :: atom()) :: t()

@spec parsec(
  t(),
  {module(), function_name :: atom()}
) :: t()

Invokes an already compiled combinator with name name in the same module.

Every parser defined via defparsec/3 or defparsecp/3 can be used as combinators. However, the defparsec/3 and defparsecp/3 functions also define an entry-point parsing function, as implied by their names. If you want to define a combinator with the sole purpose of using it in combinator, use defcombinatorp/3 instead.

Use cases

parsec/2 is useful to implement recursive definitions.

Note while parsec/2 can be used to compose smaller combinators, the preferred mechanism for doing composition is via regular functions and not via parsec/2. Let's see a practical example. Imagine that you have this module:

defmodule MyParser do
  import NimbleParsec

  date =
    integer(4)
    |> ignore(string("-"))
    |> integer(2)
    |> ignore(string("-"))
    |> integer(2)

  time =
    integer(2)
    |> ignore(string(":"))
    |> integer(2)
    |> ignore(string(":"))
    |> integer(2)
    |> optional(string("Z"))

  defparsec :datetime, date |> ignore(string("T")) |> concat(time), debug: true
end

Now imagine that you want to break date and time apart into helper functions, as you use them in other occasions. Generally speaking, you should NOT do this:

defmodule MyParser do
  import NimbleParsec

  defcombinatorp :date,
                 integer(4)
                 |> ignore(string("-"))
                 |> integer(2)
                 |> ignore(string("-"))
                 |> integer(2)

  defcombinatorp :time,
                 integer(2)
                 |> ignore(string(":"))
                 |> integer(2)
                 |> ignore(string(":"))
                 |> integer(2)
                 |> optional(string("Z"))

  defparsec :datetime,
            parsec(:date) |> ignore(string("T")) |> concat(parsec(:time))
end

The reason why the above is not recommended is because each parsec/2 combinator ends-up adding a stacktrace entry during parsing, which affects the ability of NimbleParsec to optimize code. If the goal is to compose combinators, you can do so with modules and functions:

defmodule MyParser.Helpers do
  import NimbleParsec

  def date do
    integer(4)
    |> ignore(string("-"))
    |> integer(2)
    |> ignore(string("-"))
    |> integer(2)
  end

  def time do
    integer(2)
    |> ignore(string(":"))
    |> integer(2)
    |> ignore(string(":"))
    |> integer(2)
    |> optional(string("Z"))
  end
end

defmodule MyParser do
  import NimbleParsec
  import MyParser.Helpers

  defparsec :datetime,
            date() |> ignore(string("T")) |> concat(time())
end

The implementation above will be able to compile to the most efficient format as possible without forcing new stacktrace entries.

The only situation where you should use parsec/2 for composition is when a large parser is used over and over again in a way compilation times are high. In this sense, you can use parsec/2 to improve compilation time at the cost of runtime performance. By using parsec/2, the tree size built at compile time will be reduced although runtime performance is degraded as parsec introduces a stacktrace entry.

Remote combinators

You can also reference combinators in other modules by passing a tuple with the module name and a function to parsec/2 as follows:

defmodule RemoteCombinatorModule do
  defcombinator :upcase_unicode, utf8_char([...long, list, of, unicode, chars...])
end

defmodule LocalModule do
  # Parsec that depends on `:upcase_A`
  defparsec :parsec_name,
            ...
            |> ascii_char([?a..?Z])
            |> parsec({RemoteCombinatorModule, :upcase_unicode})
end

Remote combinators are useful when breaking the compilation of large modules apart in order to use Elixir's ability to compile modules in parallel.

Examples

A good example of using parsec is with recursive parsers. A limited but recursive XML parser could be written as follows:

defmodule SimpleXML do
  import NimbleParsec

  tag = ascii_string([?a..?z, ?A..?Z], min: 1)
  text = ascii_string([not: ?<], min: 1)

  opening_tag =
    ignore(string("<"))
    |> concat(tag)
    |> ignore(string(">"))

  closing_tag =
    ignore(string("</"))
    |> concat(tag)
    |> ignore(string(">"))

  defparsec :xml,
            opening_tag
            |> repeat(lookahead_not(string("</")) |> choice([parsec(:xml), text]))
            |> concat(closing_tag)
            |> wrap()
end

SimpleXML.xml("<foo>bar</foo>")
#=> {:ok, [["foo", "bar", "foo"]], "", %{}, {1, 0}, 14}

In the example above, defparsec/3 has defined the entry-point parsing function as well as a combinator which we have invoked with parsec(:xml).

In many cases, however, you want to define recursive combinators without the entry-point parsing function. We can do this by replacing defparsec/3 by defcombinatorp:

defcombinatorp :xml,
               opening_tag
               |> repeat(lookahead_not(string("</")) |> choice([parsec(:xml), text]))
               |> concat(closing_tag)
               |> wrap()

When using defcombinatorp, you can no longer invoke SimpleXML.xml(xml) as there is no associated parsing function. You can only access the combinator above via parsec/2.

@spec post_traverse(t(), t(), call()) :: t()

Traverses the combinator results with the remote or local function call.

call is either a {module, function, args} representing a remote call, a {function, args} representing a local call or an atom function representing {function, []}.

The function given in call will receive 5 additional arguments. The rest of the parsed binary, the parser results to be post_traversed, the parser context, the current line and the current offset will be prepended to the given args. The args will be injected at the compile site and therefore must be escapable via Macro.escape/1.

The line and offset will represent the location after the combinators. To retrieve the position before the combinators, use pre_traverse/3.

The call must return a tuple {rest, acc, context} with list of results to be added to the accumulator as first argument and a context as second argument. It may also return {:error, reason} to stop processing. Notice the received results are in reverse order and must be returned in reverse order too.

The number of elements returned does not need to be the same as the number of elements given.

This is a low-level function for changing the parsed result. On top of this function, other functions are built, such as map/3 if you want to map over each individual element and not worry about ordering, reduce/3 to reduce all elements into a single one, replace/3 if you want to replace the parsed result by a single value and ignore/2 if you want to ignore the parsed result.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :letters_to_chars,
            ascii_char([?a..?z])
            |> ascii_char([?a..?z])
            |> ascii_char([?a..?z])
            |> post_traverse({:join_and_wrap, ["-"]})

  defp join_and_wrap(rest, args, context, _line, _offset, joiner) do
    {rest, args |> Enum.join(joiner) |> List.wrap(), context}
  end
end

MyParser.letters_to_chars("abc")
#=> {:ok, ["99-98-97"], "", %{}, {1, 0}, 3}

@spec pre_traverse(t(), t(), call()) :: t()

The same as post_traverse/3 but receives the line and offset from before the wrapped combinators.

post_traverse/3 should be preferred as it keeps less stack information. Use pre_traverse/3 only if you have to access the line and offset from before the given combinators.

@spec quoted_post_traverse(t(), t(), mfargs()) :: t()

Invokes call to emit the AST that post traverses the to_post_traverse combinator results.

This is similar to post_traverse/3. In post_traverse/3, call is invoked to process the combinator results. In here, it is invoked to emit AST that in its turn will process the combinator results. The invoked function must return the same types as post_traverse/3.

call is a {module, function, args} and it will receive 5 additional arguments. The AST representation of the rest of the parsed binary, the parser results, context, line and offset will be prepended to args. call is invoked at compile time and is useful in combinators that avoid injecting runtime dependencies.

The line and offset will represent the location after the combinators. To retrieve the position before the combinators, use quoted_pre_traverse/3.

This function must be used only when you want to emit code that has no runtime dependencies in other modules. In most cases, using post_traverse/3 is better, since it doesn't work on ASTs and instead works at runtime.

@spec quoted_pre_traverse(t(), t(), mfargs()) :: t()

The same as quoted_post_traverse/3 but receives the line and offset from before the wrapped combinators.

quoted_post_traverse/3 should be preferred as it keeps less stack information. Use quoted_pre_traverse/3 only if you have to access the line and offset from before the given combinators.

@spec quoted_repeat_while(t(), t(), mfargs(), opts()) :: t()

Invokes while to emit the AST that will repeat to_repeat while the AST code returns {:cont, context}.

In case repetition should stop, while must return {:halt, context}.

while is a {module, function, args} and it will receive 4 additional arguments. The AST representations of the binary to be parsed, context, line and offset will be prepended to args. while is invoked at compile time and is useful in combinators that avoid injecting runtime dependencies.

@spec reduce(t(), t(), call()) :: t()

Reduces over the combinator results with the remote or local function in call.

call is either a {module, function, args} representing a remote call, a {function, args} representing a local call or an atom function representing {function, []}.

The parser results to be reduced will be prepended to the given args. The args will be injected at the compile site and therefore must be escapable via Macro.escape/1.

See post_traverse/3 for a low level version of this function.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :letters_to_reduced_chars,
            ascii_char([?a..?z])
            |> ascii_char([?a..?z])
            |> ascii_char([?a..?z])
            |> reduce({Enum, :join, ["-"]})
end

MyParser.letters_to_reduced_chars("abc")
#=> {:ok, ["97-98-99"], "", %{}, {1, 0}, 3}

@spec repeat(t(), t(), opts()) :: t()

Allow the combinator given on to_repeat to appear zero or more times.

Beware! Since repeat/2 allows zero entries, it cannot be used inside choice/2, because it will always succeed and may lead to unused function warnings since any further choice won't ever be attempted. For example, because repeat/2 always succeeds, the string/2 combinator below it won't ever run:

choice([
  repeat(ascii_char([?a..?z])),
  string("OK")
])

Instead of repeat/2, you may want to use times/3 with the flags :min and :max.

Also beware! If you attempt to repeat a combinator that can match nothing, like optional/2, repeat/2 will not terminate. For example, consider this combinator:

 repeat(optional(utf8_char([?a])))

This combinator will never terminate because repeat/2 chooses the empty option of optional/2 every time. Since the goal of the parser above is to parse 0 or more ?a characters, it can be represented by repeat(utf8_char([?a])), because repeat/2 allows 0 or more matches.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :repeat_lower, repeat(ascii_char([?a..?z]))
end

MyParser.repeat_lower("abcd")
#=> {:ok, [?a, ?b, ?c, ?d], "", %{}, {1, 0}, 4}

MyParser.repeat_lower("1234")
#=> {:ok, [], "1234", %{}, {1, 0}, 0}

@spec repeat_while(t(), t(), call(), opts()) :: t()

Repeats while the given remote or local function while returns {:cont, context}.

If the combinator to_repeat stops matching, then the whole repeat loop stops successfully, hence it is important to assert the terminated value after repeating.

In case repetition should stop, while must return {:halt, context}.

while is either a {module, function, args} representing a remote call, a {function, args} representing a local call or an atom function representing {function, []}.

The function given in while will receive 4 additional arguments. The rest of the binary to be parsed, the parser context, the current line and the current offset will be prepended to the given args. The args will be injected at the compile site and therefore must be escapable via Macro.escape/1.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :string_with_quotes,
            ascii_char([?"])
            |> repeat_while(
              choice([
                ~S(\") |> string() |> replace(?"),
                utf8_char([])
              ]),
              {:not_quote, []}
            )
            |> ascii_char([?"])
            |> reduce({List, :to_string, []})

  defp not_quote(<<?", _::binary>>, context, _, _), do: {:halt, context}
  defp not_quote(_, context, _, _), do: {:cont, context}
end

MyParser.string_with_quotes(~S("string with quotes \" inside"))
{:ok, ["\"string with quotes \" inside\""], "", %{}, {1, 0}, 30}

Note you can use lookahead/2 and lookahead_not/2 with repeat/2 (instead of repeat_while/3) to write a combinator that repeats while a combinator matches (or does not match). For example, the same combinator above could be written as:

defmodule MyParser do
  import NimbleParsec

  defparsec :string_with_quotes,
            ascii_char([?"])
            |> repeat(
              lookahead_not(ascii_char([?"]))
              |> choice([
                ~S(\") |> string() |> replace(?"),
                utf8_char([])
              ])
            )
            |> ascii_char([?"])
            |> reduce({List, :to_string, []})
end

MyParser.string_with_quotes(~S("string with quotes \" inside"))
{:ok, ["\"string with quotes \" inside\""], "", %{}, {1, 0}, 30}

However, repeat_while is still useful when the condition to repeat comes from the context passed around.

@spec replace(t(), t(), term()) :: t()

Replaces the output of combinator given in to_replace by a single value.

The value will be injected at the compile site and therefore must be escapable via Macro.escape/1.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :replaceable, string("T") |> replace("OTHER") |> integer(2, 2)
end

MyParser.replaceable("T12")
#=> {:ok, ["OTHER", 12], "", %{}, {1, 0}, 2}

@spec string(t(), binary()) :: t()

Defines a string binary value.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :string_t, string("T")
end

MyParser.string_t("T")
#=> {:ok, ["T"], "", %{}, {1, 0}, 1}

MyParser.string_t("not T")
#=> {:error, "expected a string \"T\"", "not T", %{}, {1, 0}, 0}

@spec tag(t(), t(), term()) :: t()

Tags the result of the given combinator in to_tag in a tuple with tag as first element.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :integer, integer(min: 1) |> tag(:integer)
end

MyParser.integer("1234")
#=> {:ok, [integer: [1234]], "", %{}, {1, 0}, 4}

Notice, however, that the integer result is wrapped in a list, because the parser is expected to emit multiple tokens. When you are sure that only a single token is emitted, you should use unwrap_and_tag/3.

@spec times(t(), t(), pos_integer() | [min_and_max()]) :: t()

Allow the combinator given on to_repeat to appear at least, at most or exactly a given amount of times.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :minimum_lower, times(ascii_char([?a..?z]), min: 2)
end

MyParser.minimum_lower("abcd")
#=> {:ok, [?a, ?b, ?c, ?d], "", %{}, {1, 0}, 4}

MyParser.minimum_lower("ab12")
#=> {:ok, [?a, ?b], "12", %{}, {1, 0}, 2}

MyParser.minimum_lower("a123")
#=> {:ok, [], "a123", %{}, {1, 0}, 0}

@spec unwrap_and_tag(t(), t(), term()) :: t()

Unwraps and tags the result of the given combinator in to_tag in a tuple with tag as first element.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :integer, integer(min: 1) |> unwrap_and_tag(:integer)
end

MyParser.integer("1234")
#=> {:ok, [integer: 1234], "", %{}, {1, 0}, 4}

In case the combinator emits greater than one token, an error will be raised. See tag/3 for more information.

@spec utf8_char(t(), [range()]) :: t()

Defines a single UTF-8 codepoint in the given ranges.

ranges is a list containing one of:

• a min..max range expressing supported codepoints
• a codepoint integer expressing a supported codepoint
• {:not, min..max} expressing not supported codepoints
• {:not, codepoint} expressing a not supported codepoint

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :digit_and_utf8,
            empty()
            |> utf8_char([?0..?9])
            |> utf8_char([])
end

MyParser.digit_and_utf8("1é")
#=> {:ok, [?1, ?é], "", %{}, {1, 0}, 2}

MyParser.digit_and_utf8("a1")
#=> {:error, "expected utf8 codepoint in the range '0' to '9', followed by utf8 codepoint", "a1", %{}, {1, 0}, 0}

@spec utf8_string(t(), [range()], pos_integer() | [min_and_max()]) :: t()

Defines an UTF8 string combinator with of exact length or min and max codepoint length.

The ranges specify the allowed characters in the UTF8 string. See utf8_char/2 for more information.

If you want a string of unknown size, use utf8_string(ranges, min: 1). If you want a literal string, use string/2.

Note that the combinator matches on codepoints, not graphemes. Therefore results may vary depending on whether the input is in nfc or nfd normalized form.

Examples

defmodule MyParser do
  import NimbleParsec

  defparsec :two_letters, utf8_string([], 2)
end

MyParser.two_letters("áé")
#=> {:ok, ["áé"], "", %{}, {1, 0}, 3}

@spec wrap(t(), t()) :: t()

Wraps the results of the given combinator in to_wrap in a list.