Eliminating C/C++ implicit conversions (algorithm-archivists#987)

SConstruct

@@ -60,7 +60,7 @@ for language, tools in languages_to_import.items():
 
 Export('env')
 
-env['CCFLAGS'] = '-Wall -Wextra -Werror -pedantic'
+env['CCFLAGS'] = '-Wall -Wextra -Werror -pedantic -Wconversion'
 env['CFLAGS'] = '-std=gnu99'
 env['CXXFLAGS'] = '-std=c++17 -Wold-style-cast'
 env['ASFLAGS'] = '--64'

contents/IFS/code/c/IFS.c

@@ -29,18 +29,18 @@ void chaos_game(struct point *in, size_t in_n, struct point *out,
 }
 
 int main() {
-    const int point_count = 10000;
+    const size_t point_count = 10000;
 
     struct point shape_points [3] = {{0.0,0.0}, {0.5,sqrt(0.75)}, {1.0,0.0}};
     struct point out_points[point_count];
 
-    srand(time(NULL));
+    srand((unsigned int)time(NULL));
 
     chaos_game(shape_points, 3, out_points, point_count);
 
     FILE *fp = fopen("sierpinksi.dat", "w+");
 
-    for (int i = 0; i < point_count; ++i) {
+    for (size_t i = 0; i < point_count; ++i) {
         fprintf(fp, "%f\t%f\n", out_points[i].x, out_points[i].y);
     }
 

contents/approximate_counting/code/c/approximate_counting.c

@@ -40,7 +40,7 @@ double increment(double v, double a)
 // It returns n(v, a), the approximate count
 double approximate_count(size_t n_items, double a)
 {
-    int v = 0;
+    double v = 0;
     for (size_t i = 0; i < n_items; ++i) {
         v = increment(v, a);
     }
@@ -61,9 +61,10 @@ void test_approximation_count(size_t n_trials, size_t n_items, double a,
     for (size_t i = 0; i < n_trials; ++i) {
         sum += approximate_count(n_items, a);
     }
-    double avg = sum / n_trials;
+    double avg = sum / (double)n_trials;
 
-    if (fabs((avg - n_items) / n_items) < threshold){
+    double items = (double)n_items;
+    if (fabs((avg - items) / items) < threshold){
         printf("passed\n");
     }
     else{
@@ -73,7 +74,7 @@ void test_approximation_count(size_t n_trials, size_t n_items, double a,
 
 int main()
 {
-    srand(time(NULL));
+    srand((unsigned int)time(NULL));
 
     printf("[#]\nCounting Tests, 100 trials\n");
     printf("[#]\ntesting 1,000, a = 30, 10%% error\n");

contents/cooley_tukey/code/c/fft.c

@@ -11,7 +11,7 @@ void fft(double complex *x, size_t n) {
     memset(y, 0, sizeof(y));
     fftw_plan p;
 
-    p = fftw_plan_dft_1d(n, (fftw_complex*)x, (fftw_complex*)y,
+    p = fftw_plan_dft_1d((int)n, (fftw_complex*)x, (fftw_complex*)y,
                          FFTW_FORWARD, FFTW_ESTIMATE);
 
     fftw_execute(p);
@@ -27,7 +27,7 @@ void dft(double complex *X, const size_t N) {
     for (size_t i = 0; i < N; ++i) {
         tmp[i] = 0;
         for (size_t j = 0; j < N; ++j) {
-            tmp[i] += X[j] * cexp(-2.0 * M_PI * I * j * i / N);
+            tmp[i] += X[j] * cexp(-2.0 * M_PI * I * (double)j * (double)i / (double)N);
         }
     }
 
@@ -49,7 +49,7 @@ void cooley_tukey(double complex *X, const size_t N) {
         cooley_tukey(X + N / 2, N / 2);
 
         for (size_t i = 0; i < N / 2; ++i) {
-            X[i + N / 2] = X[i] - cexp(-2.0 * I * M_PI * i / N) * X[i + N / 2];
+            X[i + N / 2] = X[i] - cexp(-2.0 * I * M_PI * (double)i / (double)N) * X[i + N / 2];
             X[i] -= (X[i + N / 2]-X[i]);
         }
     }
@@ -58,7 +58,7 @@ void cooley_tukey(double complex *X, const size_t N) {
 void bit_reverse(double complex *X, size_t N) {
     for (size_t i = 0; i < N; ++i) {
         size_t n = i;
-        int a = i;
+        size_t a = i;
         int count = (int)log2((double)N) - 1;
 
         n >>= 1;
@@ -67,7 +67,7 @@ void bit_reverse(double complex *X, size_t N) {
             count--;
             n >>= 1;
         }
-        n = (a << count) & ((1 << (int)log2((double)N)) - 1);
+        n = (a << count) & (size_t)((1 << (size_t)log2((double)N)) - 1);
 
         if (n > i) {
             double complex tmp = X[i];
@@ -81,8 +81,8 @@ void iterative_cooley_tukey(double complex *X, size_t N) {
     bit_reverse(X, N);
 
     for (int i = 1; i <= log2((double)N); ++i) {
-        size_t stride = pow(2, i);
-        double complex w = cexp(-2.0 * I * M_PI / stride);
+        size_t stride = (size_t)pow(2, i);
+        double complex w = cexp(-2.0 * I * M_PI / (double)stride);
         for (size_t j = 0; j < N; j += stride) {
             double complex v = 1.0;
             for (size_t k = 0; k < stride / 2; ++k) {
@@ -105,7 +105,7 @@ void approx(double complex *X, double complex *Y, size_t N) {
 }
 
 int main() {
-    srand(time(NULL));
+    srand((unsigned int)time(NULL));
     double complex x[64], y[64], z[64];
     for (size_t i = 0; i < 64; ++i) {
         x[i] = rand() / (double) RAND_MAX;

contents/cooley_tukey/code/cpp/fft.cpp

@@ -55,7 +55,7 @@ void cooley_tukey(Iter first, Iter last) {
 
     // now combine each of those halves with the butterflies
     for (int k = 0; k < size / 2; ++k) {
-      auto w = std::exp(complex(0, -2.0 * pi * k / size));
+      auto w = std::exp(complex(0, -2.0 * pi * k / static_cast<double>(size)));
 
       auto& bottom = first[k];
       auto& top = first[k + size / 2];
@@ -78,7 +78,7 @@ void sort_by_bit_reverse(Iter first, Iter last) {
     b = (((b & 0xcccccccc) >> 2) | ((b & 0x33333333) << 2));
     b = (((b & 0xf0f0f0f0) >> 4) | ((b & 0x0f0f0f0f) << 4));
     b = (((b & 0xff00ff00) >> 8) | ((b & 0x00ff00ff) << 8));
-    b = ((b >> 16) | (b << 16)) >> (32 - std::uint32_t(log2(size)));
+    b = ((b >> 16) | (b << 16)) >> (32 - std::uint32_t(log2(static_cast<double>(size))));
     if (b > i) {
       swap(first[b], first[i]);
     }

contents/forward_euler_method/code/c/euler.c

@@ -13,7 +13,7 @@ void solve_euler(double timestep, double *result, size_t n) {
 int check_result(double *result, size_t n, double threshold, double timestep) {
     int is_approx = 1;
     for (size_t i = 0; i < n; ++i) {
-        double solution = exp(-3.0 * i * timestep);
+        double solution = exp(-3.0 * (double)i * timestep);
         if (fabs(result[i] - solution) > threshold) {
             printf("%f    %f\n", result[i], solution);
             is_approx = 0;

contents/forward_euler_method/code/cpp/euler.cpp

@@ -27,7 +27,7 @@ template <typename Iter>
 bool check_result(Iter first, Iter last, double threshold, double timestep) {
   auto it = first;
   for (size_t idx = 0; it != last; ++idx, ++it) {
-    double solution = std::exp(-3.0 * idx * timestep);
+    double solution = std::exp(-3.0 * static_cast<double>(idx) * timestep);
     if (std::abs(*it - solution) > threshold) {
       std::cout << "We found a value outside the threshold; the " << idx
                 << "-th value was " << *it << ", but the expected solution was "

contents/gaussian_elimination/code/cpp/gaussian_elimination.cpp

@@ -7,12 +7,12 @@
 
 void gaussianElimination(std::vector<std::vector<double> > &eqns) {
   // 'eqns' is the matrix, 'rows' is no. of vars
-  int rows = eqns.size(), cols = eqns[0].size();
+  std::size_t rows = eqns.size(), cols = eqns[0].size();
 
-  for (int i = 0; i < rows - 1; i++) {
-    int pivot = i;
+  for (std::size_t i = 0; i < rows - 1; i++) {
+      std::size_t pivot = i;
 
-    for (int j = i + 1; j < rows; j++) {
+    for (std::size_t j = i + 1; j < rows; j++) {
       if (fabs(eqns[j][i]) > fabs(eqns[pivot][i])) pivot = j;
     }
 
@@ -22,10 +22,10 @@ void gaussianElimination(std::vector<std::vector<double> > &eqns) {
     if (i != pivot)  // Swapping the rows if new row with higher maxVals is found
       std::swap(eqns[pivot], eqns[i]);  // C++ swap function
 
-    for (int j = i + 1; j < rows; j++) {
+    for (std::size_t j = i + 1; j < rows; j++) {
       double scale = eqns[j][i] / eqns[i][i];
 
-      for (int k = i + 1; k < cols; k++)   // k doesn't start at 0, since
+      for (std::size_t k = i + 1; k < cols; k++)   // k doesn't start at 0, since
         eqns[j][k] -= scale * eqns[i][k];  // values before from 0 to i
                                            // are already 0
       eqns[j][i] = 0.0;
@@ -35,17 +35,17 @@ void gaussianElimination(std::vector<std::vector<double> > &eqns) {
 
 void gaussJordan(std::vector<std::vector<double> > &eqns) {
   // 'eqns' is the (Row-echelon) matrix, 'rows' is no. of vars
-  int rows = eqns.size();
+  std::size_t rows = eqns.size();
 
-  for (int i = rows - 1; i >= 0; i--) {
+  for (std::size_t i = rows - 1; i < rows; i--) {
 
     if (eqns[i][i] != 0) {
 
       eqns[i][rows] /= eqns[i][i];
       eqns[i][i] = 1;  // We know that the only entry in this row is 1
 
       // subtracting rows from below
-      for (int j = i - 1; j >= 0; j--) {
+      for (std::size_t j = i - 1; j < i; j--) {
         eqns[j][rows] -= eqns[j][i] * eqns[i][rows];
         eqns[j][i] = 0;  // We also set all the other values in row to 0 directly
       }
@@ -55,13 +55,13 @@ void gaussJordan(std::vector<std::vector<double> > &eqns) {
 
 std::vector<double> backSubs(const std::vector<std::vector<double> > &eqns) {
   // 'eqns' is matrix, 'rows' is no. of variables
-  int rows = eqns.size();
+  std::size_t rows = eqns.size();
 
   std::vector<double> ans(rows);
-  for (int i = rows - 1; i >= 0; i--) {
+  for (std::size_t i = rows - 1; i < rows; i--) {
     double sum = 0.0;
 
-    for (int j = i + 1; j < rows; j++) sum += eqns[i][j] * ans[j];
+    for (std::size_t j = i + 1; j < rows; j++) sum += eqns[i][j] * ans[j];
 
     if (eqns[i][i] != 0)
       ans[i] = (eqns[i][rows] - sum) / eqns[i][i];

contents/graham_scan/code/c/graham.c

@@ -36,8 +36,8 @@ void polar_angles_sort(struct point *points, struct point origin, size_t size) {
 
     double pivot_angle = polar_angle(origin, points[size / 2]);
 
-    int i = 0;
-    int j = size - 1;
+    size_t i = 0;
+    size_t j = size - 1;
     while (1) {
         while (polar_angle(origin, points[i]) < pivot_angle) {
             i++;

contents/huffman_encoding/code/c/huffman.c

@@ -23,8 +23,8 @@ struct codebook {
 
 struct heap {
     struct tree** data;
-    int length;
-    int capacity;
+    size_t length;
+    size_t capacity;
 };
 
 bool is_leaf(const struct tree* t) {
@@ -39,21 +39,21 @@ void swap(struct tree** lhs, struct tree** rhs) {
 
 /* The two concat functions are horribly inefficient */
 void concat(char** dst, const char* src) {
-    int dst_len = strlen(*dst);
-    int src_len = strlen(src);
+    size_t dst_len = strlen(*dst);
+    size_t src_len = strlen(src);
     *dst = realloc(*dst, src_len + dst_len + 1);
     strcat(*dst, src);
 }
 
 void concat_char(char** dst, char c) {
-    int len = strlen(*dst);
+    size_t len = strlen(*dst);
     *dst = realloc(*dst, len + 2);
     (*dst)[len] = c;
     (*dst)[len + 1] = '\0';
 }
 
 char* duplicate(const char* src) {
-    int length = strlen(src);
+    size_t length = strlen(src);
     char* dst = malloc(length + 1);
     memcpy(dst, src, length + 1);
     return dst;
@@ -66,9 +66,9 @@ void heap_push(struct heap* heap, struct tree* value) {
     }
     heap->data[heap->length++] = value;
 
-    int index = heap->length - 1;
+    size_t index = heap->length - 1;
     while (index) {
-        int parent_index = (index - 1) / 2;
+        size_t parent_index = (index - 1) / 2;
         if (heap->data[parent_index]->count <= heap->data[index]->count) {
             break;
         }
@@ -86,11 +86,11 @@ struct tree* heap_pop(struct heap* heap) {
     struct tree* result = heap->data[0];
     swap(&heap->data[0], &heap->data[--heap->length]);
 
-    int index = 0;
+    size_t index = 0;
     for (;;) {
-        int target = index;
-        int left = 2 * index + 1;
-        int right = left + 1;
+        size_t target = index;
+        size_t left = 2 * index + 1;
+        size_t right = left + 1;
 
         if (left < heap->length &&
                 heap->data[left]->count < heap->data[target]->count) {

contents/monte_carlo_integration/code/c/monte_carlo.c

@@ -24,7 +24,7 @@ double monte_carlo(unsigned int samples) {
 }
 
 int main() {
-    srand(time(NULL));
+    srand((unsigned int)time(NULL));
 
     double estimate = monte_carlo(1000000);
 

contents/split-operator_method/code/c/split_op.c

@@ -34,10 +34,10 @@ void fft(double complex *x, size_t n, bool inverse) {
     fftw_plan p;
 
     if (inverse) {
-        p = fftw_plan_dft_1d(n, (fftw_complex*)x, (fftw_complex*)y,
+        p = fftw_plan_dft_1d((int)n, (fftw_complex*)x, (fftw_complex*)y,
                              FFTW_BACKWARD, FFTW_ESTIMATE);
     } else {
-        p = fftw_plan_dft_1d(n, (fftw_complex*)x, (fftw_complex*)y,
+        p = fftw_plan_dft_1d((int)n, (fftw_complex*)x, (fftw_complex*)y,
                              FFTW_FORWARD, FFTW_ESTIMATE);
     }
 
@@ -63,9 +63,9 @@ void init_params(struct params *par, double xmax, unsigned int res, double dt,
     par->im_time = im;
 
     for (size_t i = 0; i < res; ++i) {
-        par->x[i] = xmax / res - xmax + i * (2.0 * xmax / res);
+        par->x[i] = xmax / res - xmax + (double)i * (2.0 * xmax / res);
         if (i < res / 2) {
-            par->k[i] = i * M_PI / xmax;
+            par->k[i] = (double)i * M_PI / xmax;
         } else {
             par->k[i] = ((double)i - res) * M_PI / xmax;
         }

contents/split-operator_method/code/cpp/split_op.cpp

@@ -28,9 +28,9 @@ struct Params {
         im_time = im;
 
         for (size_t i = 0; i < res; ++i) {
-            x.emplace_back(xmax / res - xmax + i * (2.0 * xmax / res));
+            x.emplace_back(xmax / res - xmax + static_cast<double>(i) * (2.0 * xmax / res));
             if (i < res / 2) {
-                k.push_back(i * M_PI / xmax);
+                k.push_back(static_cast<double>(i) * M_PI / xmax);
             } else {
                 k.push_back((static_cast<double>(i) - res) * M_PI / xmax);
             }
@@ -85,7 +85,7 @@ void fft(vector_complex &x, bool inverse) {
 
     fftw_complex *in = reinterpret_cast<fftw_complex*>(x.data());
     fftw_complex *out = reinterpret_cast<fftw_complex*>(y.data());
-    p = fftw_plan_dft_1d(x.size(), in, out,
+    p = fftw_plan_dft_1d(static_cast<int>(x.size()), in, out,
                          (inverse ? FFTW_BACKWARD : FFTW_FORWARD), FFTW_ESTIMATE);
 
     fftw_execute(p);

contents/stable_marriage_problem/code/c/stable_marriage.c

@@ -5,15 +5,15 @@
 #include <time.h>
 
 struct person {
-    int id;
+    size_t id;
     struct person *partner;
     size_t *prefers;
     size_t index;
 };
 
 void shuffle(size_t *array, size_t size) {
     for (size_t i = size - 1; i > 0; --i) {
-        size_t j = rand() % (i + 1);
+        size_t j = (size_t)rand() % (i + 1);
         size_t tmp = array[i];
         array[i] = array[j];
         array[j] = tmp;
@@ -82,7 +82,7 @@ void free_group(struct person *group, size_t size) {
 }
 
 int main() {
-    srand(time(NULL));
+    srand((unsigned int)time(NULL));
 
     struct person men[5], women[5];
 
@@ -114,7 +114,7 @@ int main() {
     printf("\n");
 
     for (size_t i = 0; i < 5; ++i) {
-        printf("the partner of man %zu is woman %d\n", i, men[i].partner->id);
+        printf("the partner of man %zu is woman %ld\n", i, men[i].partner->id);
     }
 
     free_group(men, 5);