fix needless-range and clippy::ptr_arg warnings. (#36)

* Fix needless for loop range

* Do not ignore clippy::ptr_arg

src/naive_bayes/bernoulli.rs

@@ -134,8 +134,8 @@ impl<T: RealNumber> BernoulliNBDistribution<T> {
         let mut feature_in_class_counter = vec![vec![T::zero(); n_features]; class_labels.len()];
 
         for (row, class_index) in row_iter(x).zip(indices) {
-            for idx in 0..n_features {
-                feature_in_class_counter[class_index][idx] += row[idx];
+            for (idx, row_i) in row.iter().enumerate().take(n_features) {
+                feature_in_class_counter[class_index][idx] += *row_i;
             }
         }
 

src/naive_bayes/gaussian.rs

@@ -119,9 +119,9 @@ impl<T: RealNumber> GaussianNBDistribution<T> {
             .into_iter()
             .map(|v| {
                 let mut m = M::zeros(v.len(), n_features);
-                for row in 0..v.len() {
-                    for col in 0..n_features {
-                        m.set(row, col, v[row][col]);
+                for (row_i, v_i) in v.iter().enumerate() {
+                    for (col_j, v_i_j) in v_i.iter().enumerate().take(n_features) {
+                        m.set(row_i, col_j, *v_i_j);
                     }
                 }
                 m

src/naive_bayes/multinomial.rs

@@ -122,8 +122,8 @@ impl<T: RealNumber> MultinomialNBDistribution<T> {
         let mut feature_in_class_counter = vec![vec![T::zero(); n_features]; class_labels.len()];
 
         for (row, class_index) in row_iter(x).zip(indices) {
-            for idx in 0..n_features {
-                feature_in_class_counter[class_index][idx] += row[idx];
+            for (idx, row_i) in row.iter().enumerate().take(n_features) {
+                feature_in_class_counter[class_index][idx] += *row_i;
             }
         }