finished ch6

data_types.md

@@ -916,4 +916,36 @@ if you want nothing to happen from the ignore all then return a unit type from t
 
 for example the arm _ => () does this, this should not be used in the case of a match trying to return something
 
-# If Let
+# Concise Flow Control with if let
+
+This is a concise way of handling the  case where there is only 1 arm and the rest are ignored using _ 
+
+this would look like 
+```rust
+    let config_max = Some(3u8); // Option<u8> is the value owned by the variable
+    match config_max {
+        Some(max) => println!("The maximum is configured to be {max}"),
+        _ => (), // annoying boilerplate
+    }
+```
+
+here is how to remove the boilerplate with a if let
+this behaves just like the match above
+```rust
+    let config_max = Some(3u8);
+    if let Some(max) = config_max {
+        println!("The maximum is configured to be {max}");
+    }
+```
+
+if let is separated by an =
+the max binds to the value in option u8 then max can be used in the body of the if let
+
+the block doesn't run if the pattern doesn't match exactly
+this reduces the amount of typing and boilerplate but you lose the exhaustive nature of match which is enforced
+
+if let is a good refactor to when conciseness is preferred and working module/function is "done"
+
+should be used when only matching against one pattern and only EVER ONE pattern
+
+good to get rid of too verbose code