# parseutils

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This module contains helpers for parsing tokens, numbers, integers, floats, identifiers, etc.

To unpack raw bytes look at the streams module.

    let logs = @["2019-01-10: OK_", "2019-01-11: FAIL_", "2019-01: aaaa"]
    var outp: seq[string]

    for log in logs:
      var res: string
      if parseUntil(log, res, ':') == 10: # YYYY-MM-DD == 10
        outp.add(res & " - " & captureBetween(log, ' ', '_'))
    doAssert outp == @["2019-01-10 - OK", "2019-01-11 - FAIL"]

    from strutils import Digits, parseInt

    let
      input1 = "2019 school start"
      input2 = "3 years back"
      startYear = input1[0 .. skipWhile(input1, Digits)-1] # 2019
      yearsBack = input2[0 .. skipWhile(input2, Digits)-1] # 3
      examYear = parseInt(startYear) + parseInt(yearsBack)
    doAssert "Examination is in " & $examYear == "Examination is in 2022"

See also:

- strutils module for combined and identical parsing proc's
- json module for a JSON parser
- parsecfg module for a configuration file parser
- parsecsv module for a simple CSV (comma separated value) parser
- parseopt module for a command line parser
- parsexml module for a XML / HTML parser
- other parsers for other parsers

# Imports

sequtils

# Types

    InterpolatedKind = enum
      ikStr,                    ## ``str`` part of the interpolated string
      ikDollar,                 ## escaped ``$`` part of the interpolated string
      ikVar,                    ## ``var`` part of the interpolated string
      ikExpr                     ## ``expr`` part of the interpolated string

  Describes for `interpolatedFragments` which part of the interpolated string is yielded; for example in "str$$$var${expr}" Source Edit

# Procs

    proc parseBin[T: SomeInteger](s: string; number: var T; start = 0; maxLen = 0): int {...}{.
        noSideEffect.}

  Parses a binary number and stores its value in `number`.

  Returns the number of the parsed characters or 0 in case of an error. If error, the value of `number` is not changed.

  If `maxLen == 0`, the parsing continues until the first non-bin character or to the end of the string. Otherwise, no more than `maxLen` characters are parsed starting from the `start` position.

  It does not check for overflow. If the value represented by the string is too big to fit into `number`, only the value of last fitting characters will be stored in `number` without producing an error.

  Examples:

      var num: int
      doAssert parseBin("0100_1110_0110_1001_1110_1101", num) == 29
      doAssert num == 5138925
      doAssert parseBin("3", num) == 0
      var num8: int8
      doAssert parseBin("0b_0100_1110_0110_1001_1110_1101", num8) == 32
      doAssert num8 == 0b11101101'i8
      doAssert parseBin("0b_0100_1110_0110_1001_1110_1101", num8, 3, 9) == 9
      doAssert num8 == 0b01001110'i8
      var num8u: uint8
      doAssert parseBin("0b_0100_1110_0110_1001_1110_1101", num8u) == 32
      doAssert num8u == 237
      var num64: int64
      doAssert parseBin("0100111001101001111011010100111001101001", num64) == 40
      doAssert num64 == 336784608873'i64

  Source Edit

    proc parseOct[T: SomeInteger](s: string; number: var T; start = 0; maxLen = 0): int {...}{.
        noSideEffect.}

  Parses an octal number and stores its value in `number`.

  Returns the number of the parsed characters or 0 in case of an error. If error, the value of `number` is not changed.

  If `maxLen == 0`, the parsing continues until the first non-oct character or to the end of the string. Otherwise, no more than `maxLen` characters are parsed starting from the `start` position.

  It does not check for overflow. If the value represented by the string is too big to fit into `number`, only the value of last fitting characters will be stored in `number` without producing an error.

  Examples:

      var num: int
      doAssert parseOct("0o23464755", num) == 10
      doAssert num == 5138925
      doAssert parseOct("8", num) == 0
      var num8: int8
      doAssert parseOct("0o_1464_755", num8) == 11
      doAssert num8 == -19
      doAssert parseOct("0o_1464_755", num8, 3, 3) == 3
      doAssert num8 == 102
      var num8u: uint8
      doAssert parseOct("1464755", num8u) == 7
      doAssert num8u == 237
      var num64: int64
      doAssert parseOct("2346475523464755", num64) == 16
      doAssert num64 == 86216859871725'i64

  Source Edit

    proc parseHex[T: SomeInteger](s: string; number: var T; start = 0; maxLen = 0): int {...}{.
        noSideEffect.}

  Parses a hexadecimal number and stores its value in `number`.

  Returns the number of the parsed characters or 0 in case of an error. If error, the value of `number` is not changed.

  If `maxLen == 0`, the parsing continues until the first non-hex character or to the end of the string. Otherwise, no more than `maxLen` characters are parsed starting from the `start` position.

  It does not check for overflow. If the value represented by the string is too big to fit into `number`, only the value of last fitting characters will be stored in `number` without producing an error.

  Examples:

      var num: int
      doAssert parseHex("4E_69_ED", num) == 8
      doAssert num == 5138925
      doAssert parseHex("X", num) == 0
      doAssert parseHex("#ABC", num) == 4
      var num8: int8
      doAssert parseHex("0x_4E_69_ED", num8) == 11
      doAssert num8 == 0xED'i8
      doAssert parseHex("0x_4E_69_ED", num8, 3, 2) == 2
      doAssert num8 == 0x4E'i8
      var num8u: uint8
      doAssert parseHex("0x_4E_69_ED", num8u) == 11
      doAssert num8u == 237
      var num64: int64
      doAssert parseHex("4E69ED4E69ED", num64) == 12
      doAssert num64 == 86216859871725'i64

  Source Edit

    proc parseIdent(s: string; ident: var string; start = 0): int {...}{.raises: [],
        tags: [].}

  Parses an identifier and stores it in `ident`. Returns the number of the parsed characters or 0 in case of an error.

  Examples:

      var res: string
      doAssert parseIdent("Hello World", res, 0) == 5
      doAssert res == "Hello"
      doAssert parseIdent("Hello World", res, 1) == 4
      doAssert res == "ello"
      doAssert parseIdent("Hello World", res, 6) == 5
      doAssert res == "World"

  Source Edit

    proc parseIdent(s: string; start = 0): string {...}{.raises: [], tags: [].}

  Parses an identifier and returns it or an empty string in case of an error.

  Examples:

      doAssert parseIdent("Hello World", 0) == "Hello"
      doAssert parseIdent("Hello World", 1) == "ello"
      doAssert parseIdent("Hello World", 5) == ""
      doAssert parseIdent("Hello World", 6) == "World"

  Source Edit

    proc skipWhitespace(s: string; start = 0): int {...}{.inline, raises: [], tags: [].}

  Skips the whitespace starting at `s[start]`. Returns the number of skipped characters.

  Examples:

      doAssert skipWhitespace("Hello World", 0) == 0
      doAssert skipWhitespace(" Hello World", 0) == 1
      doAssert skipWhitespace("Hello World", 5) == 1
      doAssert skipWhitespace("Hello  World", 5) == 2

  Source Edit

    proc skip(s, token: string; start = 0): int {...}{.inline, raises: [], tags: [].}

  Skips the `token` starting at `s[start]`. Returns the length of `token` or 0 if there was no `token` at `s[start]`.

  Examples:

      doAssert skip("2019-01-22", "2019", 0) == 4
      doAssert skip("2019-01-22", "19", 0) == 0
      doAssert skip("2019-01-22", "19", 2) == 2
      doAssert skip("CAPlow", "CAP", 0) == 3
      doAssert skip("CAPlow", "cap", 0) == 0

  Source Edit

    proc skipIgnoreCase(s, token: string; start = 0): int {...}{.raises: [], tags: [].}

  Same as `skip` but case is ignored for token matching.

  Examples:

      doAssert skipIgnoreCase("CAPlow", "CAP", 0) == 3
      doAssert skipIgnoreCase("CAPlow", "cap", 0) == 3

  Source Edit

    proc skipUntil(s: string; until: set[char]; start = 0): int {...}{.inline,
        raises: [], tags: [].}

  Skips all characters until one char from the set `until` is found or the end is reached. Returns number of characters skipped.

  Examples:

      doAssert skipUntil("Hello World", {'W', 'e'}, 0) == 1
      doAssert skipUntil("Hello World", {'W'}, 0) == 6
      doAssert skipUntil("Hello World", {'W', 'd'}, 0) == 6

  Source Edit

    proc skipUntil(s: string; until: char; start = 0): int {...}{.inline, raises: [],
        tags: [].}

  Skips all characters until the char `until` is found or the end is reached. Returns number of characters skipped.

  Examples:

      doAssert skipUntil("Hello World", 'o', 0) == 4
      doAssert skipUntil("Hello World", 'o', 4) == 0
      doAssert skipUntil("Hello World", 'W', 0) == 6
      doAssert skipUntil("Hello World", 'w', 0) == 11

  Source Edit

    proc skipWhile(s: string; toSkip: set[char]; start = 0): int {...}{.inline,
        raises: [], tags: [].}

  Skips all characters while one char from the set `token` is found. Returns number of characters skipped.

  Examples:

      doAssert skipWhile("Hello World", {'H', 'e'}) == 2
      doAssert skipWhile("Hello World", {'e'}) == 0
      doAssert skipWhile("Hello World", {'W', 'o', 'r'}, 6) == 3

  Source Edit

    proc parseUntil(s: string; token: var string; until: set[char]; start = 0): int {...}{.
        inline, raises: [], tags: [].}

  Parses a token and stores it in `token`. Returns the number of the parsed characters or 0 in case of an error. A token consists of the characters notin `until`.

  Examples:

      var myToken: string
      doAssert parseUntil("Hello World", myToken, {'W', 'o', 'r'}) == 4
      doAssert myToken == "Hell"
      doAssert parseUntil("Hello World", myToken, {'W', 'r'}) == 6
      doAssert myToken == "Hello "
      doAssert parseUntil("Hello World", myToken, {'W', 'r'}, 3) == 3
      doAssert myToken == "lo "

  Source Edit

    proc parseUntil(s: string; token: var string; until: char; start = 0): int {...}{.
        inline, raises: [], tags: [].}

  Parses a token and stores it in `token`. Returns the number of the parsed characters or 0 in case of an error. A token consists of any character that is not the `until` character.

  Examples:

      var myToken: string
      doAssert parseUntil("Hello World", myToken, 'W') == 6
      doAssert myToken == "Hello "
      doAssert parseUntil("Hello World", myToken, 'o') == 4
      doAssert myToken == "Hell"
      doAssert parseUntil("Hello World", myToken, 'o', 2) == 2
      doAssert myToken == "ll"

  Source Edit

    proc parseUntil(s: string; token: var string; until: string; start = 0): int {...}{.
        inline, raises: [], tags: [].}

  Parses a token and stores it in `token`. Returns the number of the parsed characters or 0 in case of an error. A token consists of any character that comes before the `until` token.

  Examples:

      var myToken: string
      doAssert parseUntil("Hello World", myToken, "Wor") == 6
      doAssert myToken == "Hello "
      doAssert parseUntil("Hello World", myToken, "Wor", 2) == 4
      doAssert myToken == "llo "

  Source Edit

    proc parseWhile(s: string; token: var string; validChars: set[char]; start = 0): int {...}{.
        inline, raises: [], tags: [].}

  Parses a token and stores it in `token`. Returns the number of the parsed characters or 0 in case of an error. A token consists of the characters in `validChars`.

  Examples:

      var myToken: string
      doAssert parseWhile("Hello World", myToken, {'W', 'o', 'r'}, 0) == 0
      doAssert myToken.len() == 0
      doAssert parseWhile("Hello World", myToken, {'W', 'o', 'r'}, 6) == 3
      doAssert myToken == "Wor"

  Source Edit

    proc captureBetween(s: string; first: char; second = '\x00'; start = 0): string {...}{.
        raises: [], tags: [].}

  Finds the first occurrence of `first`, then returns everything from there up to `second` (if `second` is '0', then `first` is used).

  Examples:

      doAssert captureBetween("Hello World", 'e') == "llo World"
      doAssert captureBetween("Hello World", 'e', 'r') == "llo Wo"
      doAssert captureBetween("Hello World", 'l', start = 6) == "d"

  Source Edit

    proc parseBiggestInt(s: string; number: var BiggestInt; start = 0): int {...}{.
        gcsafe, extern: "npuParseBiggestInt", noSideEffect, raises: [ValueError],
        tags: [].}

  Parses an integer starting at `start` and stores the value into `number`. Result is the number of processed chars or 0 if there is no integer. `ValueError` is raised if the parsed integer is out of the valid range.

  Examples:

      var res: BiggestInt
      doAssert parseBiggestInt("9223372036854775807", res, 0) == 19
      doAssert res == 9223372036854775807'i64

  Source Edit

    proc parseInt(s: string; number: var int; start = 0): int {...}{.gcsafe,
        extern: "npuParseInt", noSideEffect, raises: [ValueError], tags: [].}

  Parses an integer starting at `start` and stores the value into `number`. Result is the number of processed chars or 0 if there is no integer. `ValueError` is raised if the parsed integer is out of the valid range.

  Examples:

      var res: int
      doAssert parseInt("2019", res, 0) == 4
      doAssert res == 2019
      doAssert parseInt("2019", res, 2) == 2
      doAssert res == 19

  Source Edit

    proc parseSaturatedNatural(s: string; b: var int; start = 0): int {...}{.raises: [],
        tags: [].}

  Parses a natural number into `b`. This cannot raise an overflow error. `high(int)` is returned for an overflow. The number of processed character is returned. This is usually what you really want to use instead of parseInt.

  Examples:

      var res = 0
      discard parseSaturatedNatural("848", res)
      doAssert res == 848

  Source Edit

    proc parseBiggestUInt(s: string; number: var BiggestUInt; start = 0): int {...}{.
        gcsafe, extern: "npuParseBiggestUInt", noSideEffect, raises: [ValueError],
        tags: [].}

  Parses an unsigned integer starting at `start` and stores the value into `number`. `ValueError` is raised if the parsed integer is out of the valid range.

  Examples:

      var res: BiggestUInt
      doAssert parseBiggestUInt("12", res, 0) == 2
      doAssert res == 12
      doAssert parseBiggestUInt("1111111111111111111", res, 0) == 19
      doAssert res == 1111111111111111111'u64

  Source Edit

    proc parseUInt(s: string; number: var uint; start = 0): int {...}{.gcsafe,
        extern: "npuParseUInt", noSideEffect, raises: [ValueError], tags: [].}

  Parses an unsigned integer starting at `start` and stores the value into `number`. `ValueError` is raised if the parsed integer is out of the valid range.

  Examples:

      var res: uint
      doAssert parseUInt("3450", res) == 4
      doAssert res == 3450
      doAssert parseUInt("3450", res, 2) == 2
      doAssert res == 50

  Source Edit

    proc parseBiggestFloat(s: string; number: var BiggestFloat; start = 0): int {...}{.
        magic: "ParseBiggestFloat", importc: "nimParseBiggestFloat", noSideEffect.}

  Parses a float starting at `start` and stores the value into `number`. Result is the number of processed chars or 0 if a parsing error occurred. Source Edit

    proc parseFloat(s: string; number: var float; start = 0): int {...}{.gcsafe,
        extern: "npuParseFloat", noSideEffect, raises: [], tags: [].}

  Parses a float starting at `start` and stores the value into `number`. Result is the number of processed chars or 0 if there occurred a parsing error.

  Examples:

      var res: float
      doAssert parseFloat("32", res, 0) == 2
      doAssert res == 32.0
      doAssert parseFloat("32.57", res, 0) == 5
      doAssert res == 32.57
      doAssert parseFloat("32.57", res, 3) == 2
      doAssert res == 57.0

  Source Edit

# Iterators

    iterator interpolatedFragments(s: string): tuple[kind: InterpolatedKind,
        value: string] {...}{.raises: [ValueError], tags: [].}

  Tokenizes the string `s` into substrings for interpolation purposes.

  Examples:

      var outp: seq[tuple[kind: InterpolatedKind, value: string]]
      for k, v in interpolatedFragments("  $this is ${an  example}  $$"):
        outp.add (k, v)
      doAssert outp ==
          @[(ikStr, "  "), (ikVar, "this"), (ikStr, " is "), (ikExpr, "an  example"),
            (ikStr, "  "), (ikDollar, "$")]

  Source Edit