View Source Mobilizon.Cldr.Number (Mobilizon v5.0.0-beta.1)

Formats numbers and currencies based upon CLDR's decimal formats specification.

The format specification is documentated in Unicode TR35. There are several classes of formatting including non-scientific, scientific, rules based (for spelling and ordinal formats), compact formats that display 1k rather than 1,000 and so on. See Cldr.Number.to_string/2 for specific formatting options.

Non-Scientific Notation Formatting

The following description applies to formats that do not use scientific notation or significant digits:

  • If the number of actual integer digits exceeds the maximum integer digits, then only the least significant digits are shown. For example, 1997 is formatted as "97" if the maximum integer digits is set to 2.

  • If the number of actual integer digits is less than the minimum integer digits, then leading zeros are added. For example, 1997 is formatted as "01997" if the minimum integer digits is set to 5.

  • If the number of actual fraction digits exceeds the maximum fraction digits, then half-even rounding it performed to the maximum fraction digits. For example, 0.125 is formatted as "0.12" if the maximum fraction digits is 2. This behavior can be changed by specifying a rounding increment and a rounding mode.

  • If the number of actual fraction digits is less than the minimum fraction digits, then trailing zeros are added. For example, 0.125 is formatted as "0.1250" if the minimum fraction digits is set to 4.

  • Trailing fractional zeros are not displayed if they occur j positions after the decimal, where j is less than the maximum fraction digits. For example, 0.10004 is formatted as "0.1" if the maximum fraction digits is four or less.

Scientific Notation Formatting

Numbers in scientific notation are expressed as the product of a mantissa and a power of ten, for example, 1234 can be expressed as 1.234 x 10^3. The mantissa is typically in the half-open interval [1.0, 10.0) or sometimes [0.0, 1.0), but it need not be. In a pattern, the exponent character immediately followed by one or more digit characters indicates scientific notation. Example: "0.###E0" formats the number 1234 as "1.234E3".

  • The number of digit characters after the exponent character gives the minimum exponent digit count. There is no maximum. Negative exponents are formatted using the localized minus sign, not the prefix and suffix from the pattern. This allows patterns such as "0.###E0 m/s". To prefix positive exponents with a localized plus sign, specify '+' between the exponent and the digits: "0.###E+0" will produce formats "1E+1", "1E+0", "1E-1", and so on. (In localized patterns, use the localized plus sign rather than '+'.)

  • The minimum number of integer digits is achieved by adjusting the exponent. Example: 0.00123 formatted with "00.###E0" yields "12.3E-4". This only happens if there is no maximum number of integer digits. If there is a maximum, then the minimum number of integer digits is fixed at one.

  • The maximum number of integer digits, if present, specifies the exponent grouping. The most common use of this is to generate engineering notation, in which the exponent is a multiple of three, for example, "##0.###E0". The number 12345 is formatted using "##0.####E0" as "12.345E3".

  • When using scientific notation, the formatter controls the digit counts using significant digits logic. The maximum number of significant digits limits the total number of integer and fraction digits that will be shown in the mantissa; it does not affect parsing. For example, 12345 formatted with "##0.##E0" is "12.3E3". Exponential patterns may not contain grouping separators.

Significant Digits

There are two ways of controlling how many digits are shows: (a) significant digits counts, or (b) integer and fraction digit counts. Integer and fraction digit counts are described above. When a formatter is using significant digits counts, it uses however many integer and fraction digits are required to display the specified number of significant digits. It may ignore min/max integer/fraction digits, or it may use them to the extent possible.

Summary

Functions

parse(string, options \\ [])

Parse a string locale-aware manner and return a number.

resolve_currencies(list, options \\ [])

Resolve curencies from strings within a list.

resolve_currency(string, options \\ [])

Resolve a currency from a string

resolve_per(string, options \\ [])

Resolve and tokenize percent or permille from the beginning and/or the end of a string

resolve_pers(list, options \\ [])

Resolve and tokenize percent and permille sybols from strings within a list.

scan(string, options \\ [])

Scans a string locale-aware manner and returns a list of strings and numbers.

to_approx_string(number, options \\ [])

Formats a number and applies the :approximately format for a locale and number system.

to_at_least_string(number, options \\ [])

Formats a number and applies the :at_least format for a locale and number system.

to_at_most_string(number, options \\ [])

Formats a number and applies the :at_most format for a locale and number system.

to_range_string(range, options \\ [])

Formats the first and last numbers of a range and applies the :range format for a locale and number system.

to_string(number, options \\ default_options())

Returns a number formatted into a string according to a format pattern and options.

to_string!(number, options \\ default_options())

Same as the execution of to_string/2 but raises an exception if an error would be returned.

validate_number_system(locale, number_system)

Return a valid number system from a provided locale and number system name or type.

Functions

Link to this function

parse(string, options \\ [])

View Source

Parse a string locale-aware manner and return a number.

Arguments

  • string is any String.t

  • options is a keyword list of options

Options

Returns

  • A number of the requested or default type or

  • {:error, {exception, error}} if no number could be determined

Notes

This function parses a string to return a number but in a locale-aware manner. It will normalise grouping characters and decimal separators, different forms of the + and - symbols that appear in Unicode and strips any _ characters that might be used for formatting in a string. It then parses the number using the Elixir standard library functions.

Examples 

iex> Mobilizon.Cldr.Number.parse("＋1.000,34", locale: "de")
{:ok, 1000.34}

iex> Mobilizon.Cldr.Number.parse("-1_000_000.34")
{:ok, -1000000.34}

iex> Mobilizon.Cldr.Number.parse("1.000", locale: "de", number: :integer)
{:ok, 1000}

iex> Mobilizon.Cldr.Number.parse("＋1.000,34", locale: "de", number: :integer)
{:error,
  {Cldr.Number.ParseError,
   "The string \"＋1.000,34\" could not be parsed as a number"}}
Link to this function

resolve_currencies(list, options \\ [])

View Source

Resolve curencies from strings within a list.

Arguments

  • list is any list in which currency names and symbols are expected

  • options is a keyword list of options

Options

  • :locale is any valid locale returned by Cldr.known_locale_names/1 or a Cldr.LanguageTag struct returned by Cldr.Locale.new!/2 The default is Mobilizon.Cldr.get_locale()

  • :only is an atom or list of atoms representing the currencies or currency types to be considered for a match. The equates to a list of acceptable currencies for parsing. See the notes below for currency types.

  • :except is an atom or list of atoms representing the currencies or currency types to be not considered for a match. This equates to a list of unacceptable currencies for parsing. See the notes below for currency types.

  • :fuzzy is a float greater than 0.0 and less than or equal to 1.0 which is used as input to String.jaro_distance/2 to determine is the provided currency string is close enough to a known currency string for it to identify definitively a currency code. It is recommended to use numbers greater than 0.8 in order to reduce false positives.

Notes

The :only and :except options accept a list of currency codes and/or currency types. The following types are recognised.

If both :only and :except are specified, the :except entries take priority - that means any entries in :except are removed from the :only entries.

  • :all, the default, considers all currencies

  • :current considers those currencies that have a :to date of nil and which also is a known ISO4217 currency

  • :historic is the opposite of :current

  • :tender considers currencies that are legal tender

  • :unannotated considers currencies that don't have "(some string)" in their names. These are usually financial instruments.

Examples 

iex> Mobilizon.Cldr.Number.scan("100 US dollars")
...> |> Mobilizon.Cldr.Number.resolve_currencies
[100, :USD]

iex> Mobilizon.Cldr.Number.scan("100 eurosports")
...> |> Mobilizon.Cldr.Number.resolve_currencies(fuzzy: 0.75)
[100, :EUR]

iex> Mobilizon.Cldr.Number.scan("100 dollars des États-Unis")
...> |> Mobilizon.Cldr.Number.resolve_currencies(locale: "fr")
[100, :USD]
Link to this function

resolve_currency(string, options \\ [])

View Source

Resolve a currency from a string

Arguments

  • list is any list in which currency names and symbols are expected

  • options is a keyword list of options

Options

  • :locale is any valid locale returned by Cldr.known_locale_names/1 or a Cldr.LanguageTag struct returned by Cldr.Locale.new!/2 The default is Mobilizon.Cldr.get_locale()

  • :only is an atom or list of atoms representing the currencies or currency types to be considered for a match. The equates to a list of acceptable currencies for parsing. See the notes below for currency types.

  • :except is an atom or list of atoms representing the currencies or currency types to be not considered for a match. This equates to a list of unacceptable currencies for parsing. See the notes below for currency types.

  • :fuzzy is a float greater than 0.0 and less than or equal to 1.0 which is used as input to String.jaro_distance/2 to determine is the provided currency string is close enough to a known currency string for it to identify definitively a currency code. It is recommended to use numbers greater than 0.8 in order to reduce false positives.

Returns

  • An ISO4217 currency code as an atom or

  • {:error, {exception, message}}

Notes

The :only and :except options accept a list of currency codes and/or currency types. The following types are recognised.

If both :only and :except are specified, the :except entries take priority - that means any entries in :except are removed from the :only entries.

  • :all, the default, considers all currencies

  • :current considers those currencies that have a :to date of nil and which also is a known ISO4217 currency

  • :historic is the opposite of :current

  • :tender considers currencies that are legal tender

  • :unannotated considers currencies that don't have "(some string)" in their names. These are usually financial instruments.

Examples 

iex> Mobilizon.Cldr.Number.resolve_currency("US dollars")
[:USD]

iex> Mobilizon.Cldr.Number.resolve_currency("100 eurosports", fuzzy: 0.75)
[:EUR]

iex> Mobilizon.Cldr.Number.resolve_currency("dollars des États-Unis", locale: "fr")
[:USD]

iex> Mobilizon.Cldr.Number.resolve_currency("not a known currency", locale: "fr")
{:error,
 {Cldr.UnknownCurrencyError,
  "The currency \"not a known currency\" is unknown or not supported"}}
Link to this function

resolve_per(string, options \\ [])

View Source (since 2.22.0) 
@spec resolve_per(String.t(), Keyword.t()) ::
  Cldr.Number.Parser.per()
  | [Cldr.Number.Parser.per() | String.t()]
  | {:error, {module(), String.t()}}

Resolve and tokenize percent or permille from the beginning and/or the end of a string

Arguments

  • list is any list in which percent and permille symbols are expected

  • options is a keyword list of options

Options

Returns

  • An :percent or permille or

  • {:error, {exception, message}}

Examples 

iex> Mobilizon.Cldr.Number.resolve_per "11%"
["11", :percent]

iex> Mobilizon.Cldr.Number.resolve_per "% of linguists"
[:percent, " of linguists"]

iex> Mobilizon.Cldr.Number.resolve_per "% of linguists %"
[:percent, " of linguists ", :percent]
Link to this function

resolve_pers(list, options \\ [])

View Source (since 2.22.0) 
@spec resolve_pers([String.t(), ...], Keyword.t()) :: [
  Cldr.Number.Parser.per() | String.t()
]

Resolve and tokenize percent and permille sybols from strings within a list.

Percent and permille symbols can be identified at the beginning and/or the end of a string.

Arguments

  • list is any list in which percent and permille symbols are expected

  • options is a keyword list of options

Options

Examples 

iex> Mobilizon.Cldr.Number.scan("100%")
...> |> Mobilizon.Cldr.Number.resolve_pers()
[100, :percent]
Link to this function

scan(string, options \\ [])

View Source

Scans a string locale-aware manner and returns a list of strings and numbers.

Arguments

  • string is any String.t

  • options is a keyword list of options

Options

  • :number is one of :integer, :float, :decimal or nil. The default is nil meaning that the type auto-detected as either an integer or a float.

  • :locale is any locale returned by Cldr.known_locale_names/1 or a Cldr.LanguageTag.t. The default is Mobilizon.Cldr.get_locale/0.

Returns

  • A list of strings and numbers

Notes

Number parsing is performed by Cldr.Number.Parser.parse/2 and any options provided are passed to that function.

Examples 

iex> Mobilizon.Cldr.Number.scan("£1_000_000.34")
["£", 1000000.34]

iex> Mobilizon.Cldr.Number.scan("I want £1_000_000 dollars")
["I want £", 1000000, " dollars"]

iex> Mobilizon.Cldr.Number.scan("The prize is 23")
["The prize is ", 23]

iex> Mobilizon.Cldr.Number.scan("The lottery number is 23 for the next draw")
["The lottery number is ", 23, " for the next draw"]

iex> Mobilizon.Cldr.Number.scan("The loss is -1.000 euros", locale: "de", number: :integer)
["The loss is ", -1000, " euros"]
Link to this function

to_approx_string(number, options \\ [])

View Source 
@spec to_approx_string(number() | Decimal.t(), Keyword.t() | Keyword.t() | map()) ::
  {:ok, String.t()} | {:error, {module(), String.t()}}

Formats a number and applies the :approximately format for a locale and number system.

Arguments

  • number is an integer, float or Decimal to be formatted

  • options is a keyword list defining how the number is to be formatted. See Cldr.Number.to_string/3 for a description of the available options.

Example 

iex> Mobilizon.Cldr.Number.to_approx_string 1234
{:ok, "~1,234"}
Link to this function

to_at_least_string(number, options \\ [])

View Source 
@spec to_at_least_string(number() | Decimal.t(), Keyword.t() | Keyword.t() | map()) ::
  {:ok, String.t()} | {:error, {module(), String.t()}}

Formats a number and applies the :at_least format for a locale and number system.

Arguments

  • number is an integer, float or Decimal to be formatted

  • options is a keyword list defining how the number is to be formatted. See Mobilizon.Cldr.Number.to_string/2 for a description of the available options.

Example 

iex> Mobilizon.Cldr.Number.to_at_least_string 1234
{:ok, "1,234+"}
Link to this function

to_at_most_string(number, options \\ [])

View Source 
@spec to_at_most_string(number() | Decimal.t(), Keyword.t() | Keyword.t() | map()) ::
  {:ok, String.t()} | {:error, {module(), String.t()}}

Formats a number and applies the :at_most format for a locale and number system.

Arguments

  • number is an integer, float or Decimal to be formatted

  • options is a keyword list defining how the number is to be formatted. See Cldr.Number.to_string/3 for a description of the available options.

Example 

iex> Mobilizon.Cldr.Number.to_at_most_string 1234
{:ok, "≤1,234"}
Link to this function

to_range_string(range, options \\ [])

View Source 
@spec to_range_string(Range.t(), Keyword.t() | Keyword.t() | map()) ::
  {:ok, String.t()} | {:error, {module(), String.t()}}

Formats the first and last numbers of a range and applies the :range format for a locale and number system.

Arguments

  • number is an integer, float or Decimal to be formatted

  • options is a keyword list defining how the number is to be formatted. See Cldr.Number.to_string/3 for a description of the available options.

Example 

iex> Mobilizon.Cldr.Number.to_range_string 1234..5678
{:ok, "1,234–5,678"}
Link to this function

to_string(number, options \\ default_options())

View Source 
@spec to_string(number() | Decimal.t(), Keyword.t() | map()) ::
  {:ok, String.t()} | {:error, {atom(), String.t()}}

Returns a number formatted into a string according to a format pattern and options.

Arguments

  • number is an integer, float or Decimal to be formatted

  • options is a keyword list defining how the number is to be formatted.

Options

  • format: the format style or a format string defining how the number is formatted. See Cldr.Number.Format for how format strings can be constructed. See Cldr.Number.Format.format_styles_for/3 to return available format styles for a locale. The default format is :standard.

  • If :format is set to :long or :short then the formatting depends on whether :currency is specified. If not specified then the number is formatted as :decimal_long or :decimal_short. If :currency is specified the number is formatted as :currency_long or :currency_short and :fractional_digits is set to 0 as a default.

  • :format may also be a format defined by CLDR's Rules Based Number Formats (RBNF). Further information is found in the module Cldr.Rbnf. The most commonly used formats in this category are to spell out the number in a the locales language. The applicable formats are :spellout, :spellout_year, :ordinal. A number can also be formatted as roman numbers by using the format :roman or :roman_lower.

  • currency: is the currency for which the number is formatted. For available currencies see Cldr.Currency.known_currencies/0. This option is required if :format is set to :currency. If currency is set and no :format is set, :format will be set to :currency as well.

  • currency_symbol: Allows overriding a currency symbol. The alternatives are:

    • :iso the ISO currency code will be used instead of the default currency symbol.
    • :narrow uses the narrow symbol defined for the locale. The same narrow symbol can be defined for more than one currency and therefore this should be used with care. If no narrow symbol is defined, the standard symbol is used.
    • :symbol uses the standard symbol defined in CLDR. A symbol is unique for each currency and can be safely used.
    • "string" uses string as the currency symbol
    • :standard (the default and recommended) uses the CLDR-defined symbol based upon the currency format for the locale.

  • :cash: a boolean which indicates whether a number being formatted as a :currency is to be considered a cash value or not. Currencies can be rounded differently depending on whether :cash is true or false. *This option is deprecated in favour of currency_digits: :cash.

  • :currency_digits indicates which of the rounding and digits should be used. The options are :accounting which is the default, :cash or :iso

  • :rounding_mode: determines how a number is rounded to meet the precision of the format requested. The available rounding modes are :down, :half_up, :half_even, :ceiling, :floor, :half_down, :up. The default is :half_even.

  • :number_system: determines which of the number systems for a locale should be used to define the separators and digits for the formatted number. If number_system is an atom then number_system is interpreted as a number system. If the :number_system is binary then it is interpreted as a number system name. See Cldr.Number.System.number_system_names_for/2. The default is :default.

  • :locale: determines the locale in which the number is formatted. See Cldr.known_locale_names/0. The default isCldr.get_locale/0 which is the locale currently in affect for this Process and which is set by Cldr.put_locale/1.

  • If :fractional_digits is set to a positive integer value then the number will be rounded to that number of digits and displayed accordingly - overriding settings that would be applied by default. For example, currencies have fractional digits defined reflecting each currencies minor unit. Setting :fractional_digits will override that setting.

  • If :maximum_integer_digits is set to a positive integer value then the number is left truncated before formatting. For example if the number 1234 is formatted with the option maximum_integer_digits: 2, the number is truncated to 34 and formatted.

  • If :round_nearest is set to a positive integer value then the number will be rounded to nearest increment of that value - overriding settings that would be applied by default.

  • :minimum_grouping_digits overrides the CLDR definition of minimum grouping digits. For example in the locale es the number 1234 is formatted by default as 1345 because the locale defines the minimium_grouping_digits as 2. If minimum_grouping_digits: 1 is set as an option the number is formatting as 1.345. The :minimum_grouping_digits is added to the grouping defined by the number format. If the sum of these two digits is greater than the number of digits in the integer (or fractional) part of the number then no grouping is performed.

  • :wrapper is a 2-arity function that will be called for each number component with parameters string and tag where tag is one of :number, :currency_symbol, :currency_space, :literal, :quote, :percent, :permille, :minus or :plus. The function must return a string. The function can be used to wrap format elements in HTML or other tags.

Locale extensions affecting formatting

A locale identifier can specify options that affect number formatting. These options are:

  • nu: defines the number system to be used if none is specified by the :number_system option to to_string/2

This key is part of the u extension and that document should be consulted for details on how to construct a locale identifier with these extensions.

Wrapping format elements

Wrapping elements is particularly useful when formatting a number with a currency symbol and the requirement is to have different HTML formatting applied to the symbol than the number. For example:

iex> Cldr.Number.to_string(100, format: :currency, currency: :USD, wrapper: fn
...>   string, :currency_symbol -> "<span class=\"symbol\">" <> string <> "</span>"
...>   string, :number -> "<span class=\"number\">" <> string <> "</span>"
...>   string, :currency_space -> "<span>" <> string <> "</span>"
...>   string, _other -> string
...> end)
{:ok, "<span class=\"symbol\">$</span><span class=\"number\">100.00</span>"}

It is also possible and recommended to use the Phoenix.HTML.Tag.content_tag/3 function if wrapping HTML tags since these will ensure HTML entities are correctly encoded. For example:

iex> Cldr.Number.to_string(100, format: :currency, currency: :USD, wrapper: fn
...>   string, :currency_symbol -> Phoenix.HTML.Tag.content_tag(:span, string, class: "symbol")
...>   string, :number -> Phoenix.HTML.Tag.content_tag(:span, string, class: "number")
...>   string, :currency_space -> Phoenix.HTML.Tag.content_tag(:span, string)
...>   string, _other -> string
...> end)
{:ok, "<span class=\"symbol\">$</span><span class=\"number\">100.00</span>"}

When formatting a number the format is parsed into format elements that might include a currency symbol, a literal string, inserted text between a currency symbol and the currency amount, a percent sign, the number itself and several other elements. In some cases it is helpful to be apply specific formatting to each element. This can be achieved by specifying a :wrapper option. This option takes a 2-arity function as an argument. For each element of the format the wrapper function is called with two parameters: the format element as a string and an atom representing the element type. The wrapper function is required to return a string that is then inserted in the final formatted number.

Returns

  • {:ok, string} or

  • {:error, {exception, message}}

Examples 

iex> Mobilizon.Cldr.Number.to_string 12345
{:ok, "12,345"}

iex> Mobilizon.Cldr.Number.to_string 12345, locale: "fr"
{:ok, "12 345"}

iex> Mobilizon.Cldr.Number.to_string 1345.32, currency: :EUR, locale: "es", minimum_grouping_digits: 1
{:ok, "1.345,32 €"}

iex> Mobilizon.Cldr.Number.to_string 1345.32, currency: :EUR, locale: "es"
{:ok, "1345,32 €"}

iex> Mobilizon.Cldr.Number.to_string 12345, locale: "fr", currency: "USD"
{:ok, "12 345,00 $US"}

iex> Mobilizon.Cldr.Number.to_string 12345, format: "#E0"
{:ok, "1.2345E4"}

iex> Mobilizon.Cldr.Number.to_string 12345, format: :accounting, currency: "THB"
{:ok, "THB 12,345.00"}

iex> Mobilizon.Cldr.Number.to_string -12345, format: :accounting, currency: "THB"
{:ok, "(THB 12,345.00)"}

iex> Mobilizon.Cldr.Number.to_string 12345, format: :accounting, currency: "THB",
...> locale: "th"
{:ok, "฿12,345.00"}

iex> Mobilizon.Cldr.Number.to_string 12345, format: :accounting, currency: "THB",
...> locale: "th", number_system: :native
{:ok, "฿๑๒,๓๔๕.๐๐"}

iex> Mobilizon.Cldr.Number.to_string 1244.30, format: :long
{:ok, "1 thousand"}

iex> Mobilizon.Cldr.Number.to_string 1244.30, format: :long, currency: "USD"
{:ok, "1,244 US dollars"}

iex> Mobilizon.Cldr.Number.to_string 1244.30, format: :short
{:ok, "1K"}

iex> Mobilizon.Cldr.Number.to_string 1244.30, format: :short, currency: "EUR"
{:ok, "€1K"}

iex> Mobilizon.Cldr.Number.to_string 1234, format: :spellout
{:ok, "one thousand two hundred thirty-four"}

iex> Mobilizon.Cldr.Number.to_string 1234, format: :spellout_verbose
{:ok, "one thousand two hundred and thirty-four"}

iex> Mobilizon.Cldr.Number.to_string 1989, format: :spellout_year
{:ok, "nineteen eighty-nine"}

iex> Mobilizon.Cldr.Number.to_string 123, format: :ordinal
{:ok, "123rd"}

iex> Mobilizon.Cldr.Number.to_string 123, format: :roman
{:ok, "CXXIII"}

iex> Mobilizon.Cldr.Number.to_string 123, locale: "th-u-nu-thai"
{:ok, "๑๒๓"}

Errors

An error tuple {:error, reason} will be returned if an error is detected. The two most likely causes of an error return are:

  • A format cannot be compiled. In this case the error tuple will look like:
    iex> Mobilizon.Cldr.Number.to_string(12345, format: "0#")
    {:error, {Cldr.FormatCompileError,
      "Decimal format compiler: syntax error before: \"#\""}}
  • The format style requested is not defined for the locale and number_system. This happens typically when the number system is :algorithmic rather than the more common :numeric. In this case the error return looks like:
    iex> Mobilizon.Cldr.Number.to_string(1234, locale: "he", number_system: "hebr", format: :percent)
    {:error, {Cldr.UnknownFormatError,
      "The locale :he with number system :hebr does not define a format :percent"}}
Link to this function

to_string!(number, options \\ default_options())

View Source 
@spec to_string!(number() | Decimal.t() | String.t(), Keyword.t() | map()) ::
  String.t() | no_return()

Same as the execution of to_string/2 but raises an exception if an error would be returned.

Arguments

Returns

  • a formatted number as a string or

  • raises an exception

Examples 

iex> Mobilizon.Cldr.Number.to_string! 12345
"12,345"

iex> Mobilizon.Cldr.Number.to_string! 12345, locale: "fr"
"12 345"
Link to this function

validate_number_system(locale, number_system)

View Source 
@spec validate_number_system(
  Cldr.Locale.locale_name() | Cldr.LanguageTag.t(),
  Cldr.Number.System.system_name() | Cldr.Number.System.types()
) :: {:ok, Cldr.Number.System.system_name()} | {:error, {module(), String.t()}}

Return a valid number system from a provided locale and number system name or type.

The number system or number system type must be valid for the given locale. If a number system type is provided, the underlying number system is returned.

Arguments

Examples 

iex> Mobilizon.Cldr.Number.validate_number_system "en", :latn
{:ok, :latn}

iex> Mobilizon.Cldr.Number.validate_number_system "en", :default
{:ok, :latn}

iex> Mobilizon.Cldr.Number.validate_number_system "en", :unknown
{:error,
 {Cldr.UnknownNumberSystemError, "The number system :unknown is unknown"}}

iex> Mobilizon.Cldr.Number.validate_number_system "zz", :default
{:error, {Cldr.InvalidLanguageError, "The language \"zz\" is invalid"}}