additions to the api. kinda drafting out what I think might be needed to the user to specify crossover and mutation behavior

inc/genetic.h

@@ -1,4 +1,5 @@
 #include <vector>
+#include <span>
 
 namespace genetic {
 
@@ -8,20 +9,27 @@ template <class T> struct Strategy {
   int num_retries; // Number of times worker threads will try to grab work pool
                    // lock before sleeping
   int batch_size;  // Number of cells a worker thread tries to evaluate in a row
-                   // before locking the pool again. 1 tends to be fine
+                   // before locking the pool again.
   int num_cells;   // Size of the population pool
   int num_generations; // Number of times (epochs) to run the algorithm
   bool test_all; // Sets whether or not every cell is tested every generation
   float test_chance; // Chance to test any given cell's fitness. Relevant only
                      // if test_all is false.
+  bool enable_crossover; // Cells that score well in the evaluation stage
+                         // produce children that replace low-scoring cells
+  bool enable_crossover_mutation;  // Mutations can occur after crossover
+  float crossover_mutation_chance; // Chance to mutate a child cell
+  int crossover_parent_num;        // Number of unique high-scoring parents in a
+                                   // crossover call.
+  int crossover_children_num;      // Number of children produced in a crossover
+  bool enable_mutation;  // Cells may be mutated before fitness evaluation
+  float mutation_chance; // Chance to mutate cells before fitness evaluation
 
   // User defined functions
   T (*make_default_cell)();
+  void (*mutate)(T &cell);
+  void (*crossover)(const std::span<T> &parents, std::span<T> &out_children);
   float (*fitness)(const T &cell);
-  void (*mutate)(const T &cell, T *out);
-  void (*crossover)(const T &a, const T &b, T *out);
-
-  float mutation_chance_per_gen;
 };
 
 template <class T> struct Stats {