[libra framework] Update comments in LBR module, use create_from_raw

Closes: aptos-labs#6065

language/stdlib/modules/LBR.move

@@ -18,18 +18,19 @@ module LBR {
     use 0x1::CoreAddresses;
     use 0x1::Errors;
     use 0x1::FixedPoint32::{Self, FixedPoint32};
-    use 0x1::Libra::{Self, Libra,
-    // RegisterNewCurrency
-    };
+    use 0x1::Libra::{Self, Libra};
     use 0x1::LibraTimestamp;
 
     /// The type tag representing the `LBR` currency on-chain.
     resource struct LBR { }
 
     /// A `ReserveComponent` holds one part of the on-chain reserve that backs
     /// `LBR` coins. Each `ReserveComponent` holds both the backing currency
-    /// itself, along with the ratio of the backing currency to the `LBR` coin.
-    /// For example, if `Coin1` makes up 1/2 of an `LBR`, then the `ratio` field would be 0.5.
+    /// itself, along with the ratio between this coin and the `LBR`.
+    /// For example, if every `LBR` coin is made up of 100 `Coin1`'s and
+    /// `1/100`'th of a `Coin2`, then the `ratio` fields of
+    /// `ReserveComponent<Coin1>` and `ReserveComponent<Coin2>` would be `100`
+    /// and `0.01` respectively.
     resource struct ReserveComponent<CoinType> {
         /// Specifies the relative ratio between the `CoinType` and `LBR` (i.e., how
         /// many `CoinType`s make up one `LBR`).
@@ -46,8 +47,8 @@ module LBR {
     /// coins, and also each reserve component that holds the backing for these coins on-chain.
     /// A crucial invariant of this on-chain reserve is that for each component
     /// `c_i`, `c_i.value/c_i.ratio >= LBR.market_cap`.
-    /// e.g., if `coin1.ratio = 1/2` and `coin2.ratio = 1/2` and `LBR.market_cap ==
-    /// 100`, then `coin1.value >= 50`, and `coin2.value >= 50`.
+    /// e.g., if `coin1.ratio = 100` and `coin2.ratio = 1/100` and `LBR.market_cap ==
+    /// 100`, then `coin1.value >= 10_000`, and `coin2.value >= 1`.
     resource struct Reserve {
         /// The mint capability allowing minting of `LBR` coins.
         mint_cap: Libra::MintCapability<LBR>,
@@ -113,11 +114,11 @@ module LBR {
         AccountLimits::publish_unrestricted_limits<LBR>(lr_account);
         let preburn_cap = Libra::create_preburn<LBR>(tc_account);
         let coin1 = ReserveComponent<Coin1> {
-            ratio: FixedPoint32::create_from_rational(1, 2),
+            ratio: FixedPoint32::create_from_raw_value(2147483648), // 2^31 = 1/2
             backing: Libra::zero<Coin1>(),
         };
         let coin2 = ReserveComponent<Coin2> {
-            ratio: FixedPoint32::create_from_rational(1, 2),
+            ratio: FixedPoint32::create_from_raw_value(2147483648), // 2^31 = 1/2
             backing: Libra::zero<Coin2>(),
         };
         move_to(lr_account, Reserve { mint_cap, burn_cap, preburn_cap, coin1, coin2 });

language/stdlib/modules/doc/LBR.md

@@ -73,8 +73,11 @@ The type tag representing the <code><a href="#0x1_LBR">LBR</a></code> currency o
 
 A <code><a href="#0x1_LBR_ReserveComponent">ReserveComponent</a></code> holds one part of the on-chain reserve that backs
 <code><a href="#0x1_LBR">LBR</a></code> coins. Each <code><a href="#0x1_LBR_ReserveComponent">ReserveComponent</a></code> holds both the backing currency
-itself, along with the ratio of the backing currency to the <code><a href="#0x1_LBR">LBR</a></code> coin.
-For example, if <code><a href="Coin1.md#0x1_Coin1">Coin1</a></code> makes up 1/2 of an <code><a href="#0x1_LBR">LBR</a></code>, then the <code>ratio</code> field would be 0.5.
+itself, along with the ratio between this coin and the <code><a href="#0x1_LBR">LBR</a></code>.
+For example, if every <code><a href="#0x1_LBR">LBR</a></code> coin is made up of 100 <code><a href="Coin1.md#0x1_Coin1">Coin1</a></code>'s and
+<code>1/100</code>'th of a <code><a href="Coin2.md#0x1_Coin2">Coin2</a></code>, then the <code>ratio</code> fields of
+<code><a href="#0x1_LBR_ReserveComponent">ReserveComponent</a>&lt;<a href="Coin1.md#0x1_Coin1">Coin1</a>&gt;</code> and <code><a href="#0x1_LBR_ReserveComponent">ReserveComponent</a>&lt;<a href="Coin2.md#0x1_Coin2">Coin2</a>&gt;</code> would be <code>100</code>
+and <code>0.01</code> respectively.
 
 
 <pre><code><b>resource</b> <b>struct</b> <a href="#0x1_LBR_ReserveComponent">ReserveComponent</a>&lt;CoinType&gt;
@@ -113,8 +116,8 @@ The on-chain reserve for the <code><a href="#0x1_LBR">LBR</a></code> holds both
 coins, and also each reserve component that holds the backing for these coins on-chain.
 A crucial invariant of this on-chain reserve is that for each component
 <code>c_i</code>, <code>c_i.value/c_i.ratio &gt;= <a href="#0x1_LBR">LBR</a>.market_cap</code>.
-e.g., if <code>coin1.ratio = 1/2</code> and <code>coin2.ratio = 1/2</code> and <code><a href="#0x1_LBR">LBR</a>.market_cap ==
-100</code>, then <code>coin1.value &gt;= 50</code>, and <code>coin2.value &gt;= 50</code>.
+e.g., if <code>coin1.ratio = 100</code> and <code>coin2.ratio = 1/100</code> and <code><a href="#0x1_LBR">LBR</a>.market_cap ==
+100</code>, then <code>coin1.value &gt;= 10_000</code>, and <code>coin2.value &gt;= 1</code>.
 
 
 <pre><code><b>resource</b> <b>struct</b> <a href="#0x1_LBR_Reserve">Reserve</a>
@@ -268,11 +271,11 @@ restrictions are enforced in the <code><a href="Libra.md#0x1_Libra_register_curr
     <a href="AccountLimits.md#0x1_AccountLimits_publish_unrestricted_limits">AccountLimits::publish_unrestricted_limits</a>&lt;<a href="#0x1_LBR">LBR</a>&gt;(lr_account);
     <b>let</b> preburn_cap = <a href="Libra.md#0x1_Libra_create_preburn">Libra::create_preburn</a>&lt;<a href="#0x1_LBR">LBR</a>&gt;(tc_account);
     <b>let</b> coin1 = <a href="#0x1_LBR_ReserveComponent">ReserveComponent</a>&lt;<a href="Coin1.md#0x1_Coin1">Coin1</a>&gt; {
-        ratio: <a href="FixedPoint32.md#0x1_FixedPoint32_create_from_rational">FixedPoint32::create_from_rational</a>(1, 2),
+        ratio: <a href="FixedPoint32.md#0x1_FixedPoint32_create_from_raw_value">FixedPoint32::create_from_raw_value</a>(2147483648), // 2^31 = 1/2
         backing: <a href="Libra.md#0x1_Libra_zero">Libra::zero</a>&lt;<a href="Coin1.md#0x1_Coin1">Coin1</a>&gt;(),
     };
     <b>let</b> coin2 = <a href="#0x1_LBR_ReserveComponent">ReserveComponent</a>&lt;<a href="Coin2.md#0x1_Coin2">Coin2</a>&gt; {
-        ratio: <a href="FixedPoint32.md#0x1_FixedPoint32_create_from_rational">FixedPoint32::create_from_rational</a>(1, 2),
+        ratio: <a href="FixedPoint32.md#0x1_FixedPoint32_create_from_raw_value">FixedPoint32::create_from_raw_value</a>(2147483648), // 2^31 = 1/2
         backing: <a href="Libra.md#0x1_Libra_zero">Libra::zero</a>&lt;<a href="Coin2.md#0x1_Coin2">Coin2</a>&gt;(),
     };
     move_to(lr_account, <a href="#0x1_LBR_Reserve">Reserve</a> { mint_cap, burn_cap, preburn_cap, coin1, coin2 });