Fix flaws in post

content/posts/2020-11-17-booleans-are-wasted-memory.md

@@ -5,10 +5,8 @@ date: "2020-11-17"
 
 A boolean is either `true` or `false`. That translates to `1` or `0`. If you think that one bit is enough to store this information, you'd be wrong.
 
-In order to keep the binary layout of a program simple and convenient, most languages store information in either 4 bit or 8 bit blocks. If you allocate a `bool` in C, you will get [an integer constant with a value of either 1 or 0](https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdbool.h.html), taking up 4 bits.
+In order to keep the binary layout of a program simple and convenient, most languages store information in 8 bit (1 byte) blocks.
-If you allocate a bool in Rust or (most) other languages that are based on LLVM, [it will take up 1 `i1`, or 8 bit of memory](https://llvm.org/docs/LangRef.html#simple-constants).
+If you allocate a `bool` in Rust or (most) other languages that are based on LLVM, [it will take up 1 `i1`, or 1 byte of memory](https://llvm.org/docs/LangRef.html#simple-constants). If you allocate a boolean value in C, you will get [an integer constant with a value of either 1 or 0](https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdbool.h.html).
-
-## There's a better way
 
 If you find yourself having to store multiple boolean states somewhere, you might simply declare those booleans and call it a day:
 
@@ -18,8 +16,8 @@ If you find yourself having to store multiple boolean states somewhere, you migh
 int main()
 {
     bool can_read = true;
-    bool can_write = false;
+    bool can_write = true;
-    bool can_execute = true;
+    bool can_execute = false;
 
     if (can_read)
         printf("read bit set\n");
@@ -34,6 +32,8 @@ int main()
 }
 ```
 
+## We can do better than this
+
 An alternative approach to store boolean values is to share a "chunk" of bits with other values. This is usually done using bitwise operations:
 
 ```c
@@ -50,8 +50,8 @@ An alternative approach to store boolean values is to share a "chunk" of bits wi
 
 int main()
 {
-    // Set permissions
+    // Allocate 1 byte for permissions
-    int permissions = PERM_READ | PERM_WRITE;
+    char permissions = PERM_READ | PERM_WRITE;
 
     if (permissions & PERM_READ)
         printf("write bit set\n");
@@ -66,9 +66,9 @@ int main()
 }
 ```
 
-This example still wastes 1 bit since we only use 3 out of 4 possible bits of the integer type, but I'm sure you get the point. Whenever you find yourself needing multiple boolean values, think twice if you can use this pattern.
+This example still wastes 5 bits since we only use 3 out of 8 possible bits of the char type, but I'm sure you get the point. Allocating 3 boolean values independently would waste 7 * 3 = 21 bits, so it's a massive improvement. Whenever you find yourself needing multiple boolean values, think twice if you can use this pattern.
 
-Microcontrollers have a very constrainted environment, therefore bitwise operations are essential in those scenarios. 7 wasted bytes are a lot if there are only 4 kb of total memory available. For larger systems we often forget about these constraints, until they add up.
+Microcontrollers have a very constrainted environment, therefore bitwise operations are essential in those scenarios. 7 wasted bits are a lot if there are only 4 kb of total memory available. For larger systems we often forget about these constraints, until they add up.
 
 ## My Plea
 * Be mindful about the software you create.