Review for changes to specification for Unified NumberFormat

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README.md

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 Intl.NumberFormat Unified API Proposal
 ======================================
 
-## Motivation
+[TC39 Stage 2 Proposal](https://docs.google.com/presentation/d/1_1D15PWniTlbLu1BOU9aDf5H87Ecq85i0CuLl5KA4DE/edit?usp=sharing)
 
-There are many requests for adding number-formatting-related features to ECMA 402.  A few of them include:
+[View Spec](https://tc39-transfer.github.io/proposal-unified-intl-numberformat/)
 
-- tc39/ecma402#200
-- tc39/ecma402#186
-- tc39/ecma402#164
-- tc39/ecma402#163
-- tc39/ecma402#95
-- tc39/ecma402#91
-- tc39/ecma402#37
-- tc39/ecma402#32
+## Background / Motivation
 
-Rather than complicate `Intl` with more subclasses with heavilly overlapping functionality, this proposal is to restructure the spec of `Intl.NumberFormat` to make it more easilly support additional features in a "unified" way.
+There are many requests for adding number-formatting-related features to ECMA-402 (the JavaScript Intl standard library). These include:
+
+- [Expose narrow currency symbol](https://github.com/tc39/ecma402/issues/200) -- Section I
+- [Clarification on behavior of SetNumberFormatDigitOptions](https://github.com/tc39/ecma402/issues/244) -- Section I
+- [Add measure unit formatting](https://github.com/tc39/ecma402/issues/32) -- Section II
+- [Add compact decimal notation](https://github.com/tc39/ecma402/issues/37) -- Section III
+- [Add scientific notation](https://github.com/tc39/ecma402/issues/164) -- Section III
+- [Add currency accounting format](https://github.com/tc39/ecma402/issues/186) -- Section IV
+- [Add option to force sign](https://github.com/tc39/ecma402/issues/163) -- Section IV
+
+These features are important to both end users and to Google.  Since most of these features require carrying along large amounts of locale data for proper i18n support, exposing these features via a JavaScript API reduces bandwidth and lowers the barrier to entry for i18n best practices.
+
+Rather than complicate `Intl` with more constructors with heavilly overlapping functionality, this proposal is to restructure the spec of `Intl.NumberFormat` to make it more easilly support additional features in a "unified" way.
+
+Additional background: [prior discussion](https://github.com/tc39/ecma402/issues/215)
+
+## I. Spec Cleanup
+
+Certain sections of the spec have been refactored with the following objectives:
+
+- Fix https://github.com/tc39/ecma402/issues/238 (currency long name has dependency on plural form, and the currency long name pattern has dependency on currencyWidth).
+- Move pattern resolution out of the constructor to keep all internal fields of NumberFormat locale-agnostic, making it easier to reason about behavior in the format method.
+- Fix https://github.com/tc39-transfer/proposal-unified-intl-numberformat/issues/2, to allow minimumIntegerDigits to control integer digit count when significant digits are used.
+
+In addition, one missing option is added to the existing `currencyDisplay` setting: "narrowSymbol", which uses the CLDR narrow-format symbol:
+
+```javascript
+(100).toLocaleString("en-CA", {
+    style: "currency",
+    currency: "USD",
+    currencyDisplay: "narrowSymbol"
+});
+// ==> "$100" (rather than "US$100")
+```
+
+## II. Units
+
+Units of measurement can be formatted as follows:
+
+```javascript
+(9.81).toLocaleString("en-US", {
+    style: "unit",
+    unit: "acceleration-meter-per-second-squared",
+    unitDisplay: "short"
+});
+// ==> "9.81 m/s²"
+```
+
+The syntax was discussed in #3.
+
+- `style` receives the string value "unit"
+- `unit` receives a string measurement unit identifier, defined in [UTS #35, Part 2, Section 6](http://unicode.org/reports/tr35/tr35-general.html#Unit_Elements).  See also the [full list of unit identifiers](https://unicode.org/repos/cldr/tags/latest/common/validity/unit.xml).
+    - Note: currently this is restricted to single units as listed in the CLDR specification.  If there is sufficient demand, a future proposal could add ways to combine units, such as compound units.  Note that certain compound units, such as "meters per second", are already available as standalone units in CLDR.
+    - Also relecant [CLDR #11271](https://unicode.org/cldr/trac/ticket/11271) about fleshing out some details on unit identifiers in the spec.
+- `unitDisplay`, named after the corresponding setting for currencies, `currencyDisplay`, takes either "narrow", "short", or "long".
+
+## III. Scientific and Compact Notation
+
+Scientific and compact notation are represented by the new option `notation` and can be formatted as follows:
+
+```javascript
+(987654321).toLocaleString("en-US", {
+    notation: "scientific"
+});
+// ==> 9.877E8
+
+(987654321).toLocaleString("en-US", {
+    notation: "engineering"
+});
+// ==> 987.7E6
+
+(987654321).toLocaleString("en-US", {
+    notation: "compact",
+    compactDisplay: "long"
+});
+// ==> 987.7 million
+```
+
+The syntax was discussed in #5.
+
+- `notation` takes either "scientific", "engineering", "compact", or "plain"
+- `compactDisplay`, used only when `notation` is "compact", takes either "short" or "long"
+
+Rounding-related settings (min/max integer/fraction digits) are applied after the number is scaled according to the chosen notation.
+
+Notation styles are allowed to be combined with other options:
+
+```javascript
+(299792458).toLocaleString("en-US", {
+    notation: "scientific",
+    minimumFractionDigits: 2,
+    maximumFractionDigits: 2,
+    style: "unit",
+    unit: "speed-meter-per-second"
+});
+// ==> 3.00E8 m/s
+```
+
+## IV. Sign Display
+
+The sign can be displayed on positive numbers:
+
+```javascript
+(55).toLocaleString("en-US", {
+    signDisplay: "always"
+});
+// ==> +55
+```
+
+Currency accounting sign display is also supported via a new option. In many locales, accounting format means to wrap the number with parentheses instead of
+appending a minus sign.  For example:
+
+```javascript
+(-100).toLocaleString("bn", {
+    style: "currency",
+    currency: "EUR",
+    currencySign: "accounting"
+});
+// ==> (১০০.০০€)
+```
+
+The syntax was discussed in #6:
+
+- `signDisplay`: "auto" (default), "always", "never", "except-zero"
+  - See examples below.
+- `currencySign`: "standard" (default), "accounting"
+  - "accounting" enables the accounting format on currency values, as shown in the example above.  "standard", the default value, disables accounting formats.
+
+Examples of signDisplay choices with Latin digits:
+
+signDisplay | -1  | 0   | 1
+----------- | --- | --- | ---
+auto        | -1  | 0   | 1
+always      | -1  | +0  | +1
+never       | 1   | 0   | 1
+except-zero | -1  | 0   | +1
+
+As usual, this may be combined with other options.
+
+```javascript
+(0.55).toLocaleString("en-US", {
+    style: "percent",
+    signDisplay: "except-zero"
+});
+// ==> +55%
+```
 
-Background: tc39/ecma402#215