ece150: add pointers part 2

docs/ce1/ece150.md

@@ -18,7 +18,7 @@ Binary numbers are prefixed with `0b`.
 To convert from **binary to decimal**, each digit should be treated as a power of two much like in the base 10 system.
 
 !!! example
-    $$
+    $$0
     \text{0b1011}=1\times2^3 + 0\times2^2+1\times2^1+1\times2^0=11
     $$
 
@@ -201,6 +201,39 @@ If deleting arrays, `delete[]` should be used instead.
 !!! warning
     Statically allocated memory **cannot be deallocated** manually as it is done so by the compiler, so differentiating the two is generally a good idea.
 
+### Vectors at home
+
+Dynamic allocation can be used to mimick an `std::vector` by creating a new array whenever an element would be full and doubling its size, copying all elements over.
+
+!!! example
+    Sample implementation:
+    
+    ```cpp
+    std::size_t capacity{10};
+    double *data{new double[capacity]};
+    std::size_t els{0};
+    
+    while (true) {
+      double x{};
+      std::cin >> x;
+      
+      ++els;
+      if (els == capacity) {
+        std::size_t old_capacity{capacity};
+        double *old_data{data};
+        capacity *= 2;
+        data = new double[capacity];
+        
+        for (int i{}; i < old_capacity; ++i) {
+          data[i] = old_data[i];
+        }
+        
+        delete[] old_data;
+        old_data = nullptr;
+      }
+    }
+    ```
+
 ### Wild pointers
 
 A wild pointer is any uninitialised pointer. Its behaviour is undefined. Accessing unallocated memory results in a **segmentation fault**, causing the OS to terminate the program.
@@ -266,3 +299,44 @@ The memory at the location of the pointer can be accessed by setting the pointer
 ```cpp
 *var = 100;
 ```
+
+The `const` modifier only makes constant the value immediately after `const`, meaning that the expression after it cannot be used as an lvalue.
+
+!!! example
+    ```cpp
+    int* const p_x{&x};
+    
+    p_x = &y;  // not allowed
+    *p_x = y;  // allowed
+    ```
+    
+    ```cpp
+    int const *p_x{&x};
+    
+    p_x = &y;  // allowed
+    *p_x = y;  // not allowed
+    ```
+    
+    ```cpp
+    int const * const p_x{&x};
+    
+    p_x = &y;  // not allowed
+    *p_x = y;  // not allowed
+    ```
+
+Pointers to `const` values must also be `const`.
+
+!!! example
+    BAD:
+    ```cpp
+    const int x = 2;
+    int *p_x{&x};
+    ```
+    
+    GOOD:
+    ```cpp
+    const int x = 2;
+    int const *p_x{&x};
+    ```
+    
+