From a6cc4056ab01c2cb652c35763fd9aa2632b04692 Mon Sep 17 00:00:00 2001
From: DanArmor <39347109+DanArmor@users.noreply.github.com>
Date: Thu, 5 Oct 2023 02:49:55 +0300
Subject: [PATCH 1/4] feat: ability to inverse weights of WalkerTableBuilder

---
 CHANGELOG.md   |  6 ++++++
 Cargo.lock     |  2 +-
 Cargo.toml     |  4 ++--
 src/builder.rs | 14 ++++++++++++++
 src/util.rs    |  1 -
 5 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bac5768..f706da2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Change Log
 
+## 0.4.2 - 2023-10-2
+
+### Changes
+
+- [#5](https://github.com/ichi-h/weighted_rand/pull/5) Thanks [@DanArmor](https://github.com/DanArmor)! - fix: return 1 for gcd_for_slice if all elements are 0.0
+
 ## 0.4.1 - 2023-7-3
 
 ### Changes
diff --git a/Cargo.lock b/Cargo.lock
index 8ff6801..f927bb3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -628,7 +628,7 @@ dependencies = [
 
 [[package]]
 name = "weighted_rand"
-version = "0.4.1"
+version = "0.4.2"
 dependencies = [
  "criterion",
  "rand",
diff --git a/Cargo.toml b/Cargo.toml
index 083e471..8632bab 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "weighted_rand"
-version = "0.4.1"
+version = "0.4.2"
 authors = ["Ichi <ichi.h3@gmail.com>"]
 description = "A weighted random sampling crate using Walker's Alias Method."
 documentation = "https://docs.rs/weighted_rand"
@@ -14,7 +14,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-serde = { version="1.0", features = ["derive"] }
+serde = { version = "1.0", features = ["derive"] }
 rand = "0.8"
 
 [dev-dependencies]
diff --git a/src/builder.rs b/src/builder.rs
index 5280c0b..c9450f2 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -86,6 +86,20 @@ impl WalkerTableBuilder {
         WalkerTable::new(aliases, probs)
     }
 
+    pub fn inverse(self) -> WalkerTableBuilder {
+        let min_value = match self.index_weights.iter().min() {
+            Some(v) => *v,
+            None => 0
+        };
+        let max_value = match self.index_weights.iter().max() {
+            Some(v) => *v,
+            None => 0
+        };
+        Self {
+            index_weights: self.index_weights.into_iter().map(|x| max_value + min_value - x).collect()
+        } 
+    }
+
     /// Calculates the sum of `index_weights`.
     fn sum(&self) -> u32 {
         self.index_weights.iter().fold(0, |acc, cur| acc + cur)
diff --git a/src/util.rs b/src/util.rs
index f454393..bbe7d14 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -14,7 +14,6 @@ pub mod math {
             return 0;
         }
 
-        let first = slice[0];
         let mut iter = slice.iter().skip_while(|x| x == &&0);
         let first = match iter.next() {
             Some(v) => *v,

From df6b5934bf412c95df383dba66c780858dcf4331 Mon Sep 17 00:00:00 2001
From: DanArmor <39347109+DanArmor@users.noreply.github.com>
Date: Sun, 8 Oct 2023 22:24:55 +0300
Subject: [PATCH 2/4] fix: prevented overflow

---
 src/builder.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/builder.rs b/src/builder.rs
index c9450f2..9d0bcad 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -96,7 +96,7 @@ impl WalkerTableBuilder {
             None => 0
         };
         Self {
-            index_weights: self.index_weights.into_iter().map(|x| max_value + min_value - x).collect()
+            index_weights: self.index_weights.into_iter().map(|x| max_value - x + min_value).collect()
         } 
     }
 

From 0269f87232fbc4dd4374cd20a175ce0c4ab71f99 Mon Sep 17 00:00:00 2001
From: DanArmor <39347109+DanArmor@users.noreply.github.com>
Date: Sun, 8 Oct 2023 22:28:28 +0300
Subject: [PATCH 3/4] docs: added comment for inverse

---
 src/builder.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/builder.rs b/src/builder.rs
index 9d0bcad..1069035 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -86,6 +86,7 @@ impl WalkerTableBuilder {
         WalkerTable::new(aliases, probs)
     }
 
+    /// Inverses given weights
     pub fn inverse(self) -> WalkerTableBuilder {
         let min_value = match self.index_weights.iter().min() {
             Some(v) => *v,

From 298aef5e69908efd5fed3be05713f4f04aef4e08 Mon Sep 17 00:00:00 2001
From: DanArmor <39347109+DanArmor@users.noreply.github.com>
Date: Sun, 8 Oct 2023 22:51:22 +0300
Subject: [PATCH 4/4] fix: min and max values during inverse

fix: min and max values during inverse
---
 src/builder.rs | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/builder.rs b/src/builder.rs
index 1069035..6ff57a9 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -90,15 +90,27 @@ impl WalkerTableBuilder {
     pub fn inverse(self) -> WalkerTableBuilder {
         let min_value = match self.index_weights.iter().min() {
             Some(v) => *v,
-            None => 0
+            None => 0,
         };
         let max_value = match self.index_weights.iter().max() {
             Some(v) => *v,
-            None => 0
+            None => 0,
         };
         Self {
-            index_weights: self.index_weights.into_iter().map(|x| max_value - x + min_value).collect()
-        } 
+            index_weights: self
+                .index_weights
+                .into_iter()
+                .map(|x| {
+                    if x == max_value {
+                        min_value
+                    } else if x == min_value {
+                        max_value
+                    } else {
+                        max_value - x
+                    }
+                })
+                .collect(),
+        }
     }
 
     /// Calculates the sum of `index_weights`.