Number and Currency Localization and Formatting
CLDR defines many different ways to format a number for different uses and defines a set of formats categorised by common pupose to make it easier to express the same intent across many different locales that represent many different territories, cultures, number systems and scripts.
See Cldr.Number, Cldr.Number.to_string/2 and Cldr.Number.to_number_system/2.
Public API
The primary api for number formatting is Cldr.Number.to_string/2. It provides the ability to format numbers in a standard way for configured locales. It also provides the means for format numbers as a currency, as a short form (like 1k instead of 1,000). Additionally it provides formats to spell a number in works, format it as roman numerals and output an ordinal number. Some examples illustrate:
iex> Cldr.Number.to_string 12345
{:ok, "12,345"}
iex> Cldr.Number.to_string 12345, locale: "fr"
{:ok, "12 345"}
iex> Cldr.Number.to_string 12345, locale: "fr", currency: "USD"
{:ok, "12 345,00 $US"}
iex(4)> Cldr.Number.to_string 12345, format: "#E0"
{:ok, "1.2345E4"}
iex> Cldr.Number.to_string 12345, format: :accounting, currency: "THB"
{:ok, "THB12,345.00"}
iex> Cldr.Number.to_string -12345, format: :accounting, currency: "THB"
{:ok, "(THB12,345.00)"}
iex> Cldr.Number.to_string 12345, format: :accounting, currency: "THB", locale: "th"
{:ok, "THB12,345.00"}
iex> Cldr.Number.to_string 12345, format: :accounting, currency: "THB", locale: "th", number_system: :native
{:ok, "THB๑๒,๓๔๕.๐๐"}
iex> Cldr.Number.to_string 1244.30, format: :long
{:ok, "1 thousand"}
iex> Cldr.Number.to_string 1244.30, format: :long, currency: "USD"
{:ok, "1,244.30 US dollars"}
iex> Cldr.Number.to_string 1244.30, format: :short
{:ok, "1K"}
iex> Cldr.Number.to_string 1244.30, format: :short, currency: "EUR"
{:ok, "€1.24K"}
iex> Cldr.Number.to_string 1234, format: :spellout
{:ok, "one thousand two hundred thirty-four"}
iex> Cldr.Number.to_string 1234, format: :spellout_verbose
{:ok, "one thousand two hundred and thirty-four"}
iex> Cldr.Number.to_string 123, format: :ordinal
{:ok, "123rd"}
iex> Cldr.Number.to_string 123, format: :roman
{:ok, "CXXIII"}Standard Formatting Styles
Cldr supports the styles of formatting defined by CLDR being:
:standardwhich formats a number if a decimal format commonly used in many locales. This is the default format.
iex> Cldr.Number.to_string 1234, format: :standard
{:ok, "1,234"}:currencywhich formats a number according to the format or a particular currency adjusted for rounding, number of decimal digits after the fraction, whether the currency is accounting or cash rounded and using the appropriate locale-specific currency symbol. This format also requires that the option:currencybe specified. Note that for currency formatting the defined rounding and fractional digits defined for the currency is used. The boolean parameter:cashcan also be specified to indicate if this is a cash amount. Some currencies, like the Swiss Franc and Australian Dollar have a smallest cash amount that is 0.05 of the Franc of Dollar and hence rouding has to take that into account.
iex> Cldr.Number.to_string 1234.31, format: :currency, currency: :CHF
{:ok, "CHF1,234.31"}
iex> Cldr.Number.to_string 1234.31, format: :currency, currency: :CHF, cash: true
{:ok, "CHF1,234.30"}:accountingwhich formats a positive number likestandardbut which usually wraps a negative number in(). The:accountingformat also requires that the:currencyoption be specified.
iex> Cldr.Number.to_string 1234, format: :accounting, currency: :THB
{:ok, "THB1,234.00"}
iex> Cldr.Number.to_string -1234, format: :accounting, currency: :THB
{:ok, "(THB1,234.00)"}:percentwhich multiplies a number by 100 and includes a locale-specific percent symbol. Usually%.
iex> Cldr.Number.to_string 0.09, format: :percent
{:ok, "9%"}:permille(aka ‘basis points’) which multiples a number by 1,000 and includes a locale specific permille symbol. Usually‰. Note that many (most?) locales don’t provide a:permilleformat definition. The alternative is to specify a format string as in the example below.
iex> Cldr.Number.to_string 0.56, format: "#‰"
{:ok, "560‰"}
iex> Cldr.Number.to_string 0.56, format: :permille
{:error,
{Cldr.UnknownFormatError,
"The locale \"en\" with number system :default does not define a format :permille."}}:scientificwhich formats a number as a mantissa and base-10 exponent.
iex> Cldr.Number.to_string 124.56, format: :scientific
{:ok, "1.2456E2"}See Cldr.Number.Formatter.Decimal.
Short and Long Formats
Cldr also supports formats that minimise publishing space or which attempt to make large number more human-readable.
:shortwhich presents a number or currency in a narrow space.
iex> Cldr.Number.to_string 12456.56, format: :short
{:ok, "12K"}
iex> Cldr.Number.to_string 12456.56, format: :short, currency: :USD
{:ok, "$12K"}:longwhich presents numbers in a sentence form adjusted for plurality and locale. For example,1,0000would be formatted as1 thousand. This is not the same as spelling out the number which is part of the Unicode CLDR Rules-Based Number Formatting. SeeCldr.Rbnf.
iex> Cldr.Number.to_string 12456.56, format: :long
{:ok, "12 thousand"}
iex> Cldr.Number.to_string 12456.56, format: :long, currency: :USD
{:ok, "12,457 US dollars"}See Cldr.Number.Formatter.Short and Cldr.Number.Formatter.Currency.
User-Specified Number Formats
User-defined decimal formats are also supported using the formats described by Unicode technical report TR35.
The formats described therein are supported by Cldr with some minor omissions and variations. Some examples of number formats are:
| Pattern | Currency | Text |
|---|---|---|
| #,##0.## | n/a | 1 234,57 |
| #,##0.### | n/a | 1 234,567 |
| ###0.##### | n/a | 1234,567 |
| ###0.0000# | n/a | 1234,5670 |
| 00000.0000 | n/a | 01234,5670 |
| 00 | n/a | 12 |
| #,##0.00 ¤ | EUR | 1 234,57 € |
See Cldr.Number and Cldr.Number.Formatter.Decimal.
Number Pattern Character Definitions
The folllowing table describes the symbols used in a number format string and is extracted from TR35
| Symbol | Location | Localized Replacement | Meaning |
|---|---|---|---|
| 0 | Number | digit | Digit |
| 1 .. 9 | Number | digit | ‘1’ through ‘9’ indicate rounding |
| @ | Number | digit | Significant digit |
| # | Number | digit, nothing | Digit, omit leading/trailing zeros |
| . | Number | decimal symbol | Decimal or monetary decimal separator |
| - | Number | minus sign | Minus sign[1] |
| , | Number | grouping separator | Decimal/monetary grouping separator[2] |
| E | Number | exponent | Separates mantissa and exponent for scientific formatting |
| + | Exponent | plus sign | Prefix positive exponent with plus sign |
| % | Pre/Suffix | percent sign | Multiply by 100 and show as a percentage |
| ‰ | Pre/Suffix | per mille | Multiply by 1000 and show as per mille (aka “basis points”) |
| ; | Subpattern | syntax only | Separates positive and negative subpatterns |
| ¤ | Pre/Suffix | currency symbol | Currency symbol[3] |
| * | Pre/Suffix | padding character | Pad escape, precedes padding character |
| ‘ | Pre/Suffix | syntax only | To quote special chars. eg ‘#’ |
Notes
[1] The pattern ‘-‘0.0 is not the same as the pattern -0.0. In the former case, the minus sign is a literal. In the latter case, it is a special symbol, which is replaced by the localised minus symbol, and can also be replaced by the plus symbol for a format like +12%.
[2] May occur in both the integer part and the fractional part. The position determines the grouping.
[3] Any sequence is replaced by the localized currency symbol for the currency being formatted, as in the table below. If present in a pattern, the monetary decimal separator and grouping separators (if available) are used instead of the numeric ones. If data is unavailable for a given sequence in a given locale, the display may fall back to ¤ or ¤¤.
| No. | Replacement Example |
|---|---|
| ¤ | Standard currency symbol as in C$12.00 |
| ¤¤ | ISO currency symbol as in CAD 12.00 |
| ¤¤¤ | Appropriate currency display name based upon locale and plural rules |
| ¤¤¤¤ | Narrow currency symbol as in $12.00 |
Rule Based Number Formats
CLDR provides an additional mechanism for the formatting of numbers. This approach can be used to format numbers in locale-specific words, or to format numbers in a number system that does not use the decimal digits 0 through 9 such as Chinese and Hebrew.
Formatting numbers as words, ordinals and roman numerals
- As words. For example, formatting 123 into “one hundred and twenty-three” for the “en” locale. The applicable format types are
:spelloutand:spellout_verbose.
iex> Cldr.Number.to_string 123, format: :spellout
{:ok, "one hundred twenty-three"}
iex> Cldr.Number.to_string 123, format: :spellout_verbose
{:ok, "one hundred and twenty-three"}- As a year. In many languages the written form of a year is different to that used for an arbitrary number. For example, formatting 1989 would result in “nineteen eighty-nine”. The applicable format type is
:spellout_year.
iex> Cldr.Number.to_string 2017, format: :spellout_year
{:ok, "twenty seventeen"}- As an ordinal. For example, formatting 123 into “123rd”. The applicable format types are
:ordinal,:spellout_ordinaland:spellout_ordinal_verbose.
iex> Cldr.Number.to_string 123, format: :ordinal
{:ok, "123rd"}
iex> Cldr.Number.to_string 123, format: :spellout_ordinal
{:ok, "one hundred twenty-third"}
iex> Cldr.Number.to_string 123, format: :spellout_ordinal_verbose
{:ok, "one hundred and twenty-third"}
iex> Cldr.Number.to_string 123, format: :ordinal, locale: "fr"
{:ok, "123e"}
iex> Cldr.Number.to_string 123, format: :ordinal, locale: "zh"
{:ok, "第123"}- As Roman numerals. For example, formatting 123 into “CXXIII”. The applicable formats are
:romanor:roman_lower. Note that roman number formatting is only supported for numbers between 1 and 5,000.
iex> Cldr.Number.to_string 123, format: :roman
{:ok, "CXXIII"}
iex(49)> Cldr.Number.to_string 123, format: :roman_lower
{:ok, "cxxiii"}Representing numbers in non-latin number systems
Some number systems, such as Hebrew and Chinese, do not use the digits 0 through 9 in the their native number system. RBNF defines rules for these and other number systems that can provide number system conversion. Cldr.Number.to_string/2 does not support number systems without digits defined therefore another mechanism is requires to output numbers in these algorithmic number systems. To support number system conversion, the function Cldr.Number.to_number_system/2 is provided. Note that no formatting is supported, this is a number system conversion only.
For example, to output a number in the :hans numbering system (Chinese) and the Hebrew number system:
iex> Cldr.Number.to_number_system 123, :hans
{:ok, "一百二十三"}
iex(56)> Cldr.Number.to_number_system 123, :hebr
{:ok, "ק׳"}Cldr.Number.to_number_system/2 supports the conversion between numeric number systems (those with digits 0 through 9) in addition to algorithmic number systems (those supported by rules-based number formatting). For example, outputting to the :thai number system:
iex> Cldr.Number.to_number_system 123, :thai
{:ok, "๑๒๓"}The known number systems in Cldr can be returned by the function Cldr.Number.System.known_number_systems/0:
iex> Cldr.Number.System.known_number_systems
[:adlm, :ahom, :arab, :arabext, :armn, :armnlow, :bali, :beng, :bhks, :brah,
:cakm, :cham, :cyrl, :deva, :ethi, :fullwide, :geor, :grek, :greklow, :gujr,
:guru, :hanidays, :hanidec, :hans, :hansfin, :hant, :hantfin, :hebr, :hmng,
:java, :jpan, :jpanfin, :kali, :khmr, :knda, :lana, :lanatham, :laoo, :latn,
:lepc, :limb, :mathbold, :mathdbl, :mathmono, :mathsanb, :mathsans, :mlym,
:modi, :mong, :mroo, ...]RBNF rules defined in CLDR
There are also many additional methods more specialised to a specific locale that cater for languages with more complex gender and grammar requirements. Since these rules are specialised to a locale it is not possible to standarise the public API more than described in this section.
The full set of RBNF formats is accessable through the modules Cldr.Rbnf.Ordinal, Cldr.Rbnf.Spellout and Cldr.Rbnf.NumberSystem.
Each of these modules has a set of functions that are generated at compile time that implement the relevant RBNF rules. The available rules for a given locale can be retrieved by calling Cldr.Rbnf.Spellout.rule_set(locale) or the same function on the other modules. For example:
iex> Cldr.Rbnf.Ordinal.rule_sets "en"
[:digits_ordinal]
iex> Cldr.Rbnf.Spellout.rule_sets "fr"
[:spellout_ordinal_masculine_plural, :spellout_ordinal_masculine,
:spellout_ordinal_feminine_plural, :spellout_ordinal_feminine,
:spellout_numbering_year, :spellout_numbering, :spellout_cardinal_masculine,
:spellout_cardinal_feminine]These rule-based formats are invoked directly on the required module passing the number and locale. For example:
iex> Cldr.Rbnf.Spellout.spellout_numbering_year 1989, "fr"
"dix-neuf-cent quatre-vingt-neuf"
iex> Cldr.Rbnf.Spellout.spellout_numbering_year 1989, "en"
"nineteen eighty-nine"
iex> Cldr.Rbnf.Ordinal.digits_ordinal 1989, "en"
"1,989th"RBNF Rules with Float numbers
RBNF is primarily oriented towards positive integer numbers. Whilst the standard caters for negative numbers and fractional numbers the implementation of the rules is incomplete. Use with care.