add new example of simple 'function' overloading using C11 _Generic keyword

21st_century_c/complex.c

@@ -0,0 +1,45 @@
+#include "cplx.h"
+#include <gsl/gsl_blas.h>
+#include <gsl/gsl_complex_math.h>
+
+
+
+gsl_vector_complex *cvec_dot_gslcplx(gsl_vector_complex *v, gsl_complex x) {
+  gsl_vector_complex *out = gsl_vector_complex_alloc(v->size);
+  for (size_t i=0; i < v->size; i++) {
+    gsl_vector_complex_set(out, i, gsl_complex_mul(x, gsl_vector_complex_get(v, i)));
+  }
+  return out;
+}
+
+
+gsl_vector_complex *vec_dot_gslcplx(gsl_vector *v, gsl_complex x) {
+  gsl_vector_complex *out = gsl_vector_complex_alloc(v->size);
+  for (size_t i=0; i < v->size; i++) {
+    gsl_vector_complex_set(out, i, gsl_complex_mul_real(x, gsl_vector_get(v, i)));
+  }
+  return out;
+}
+
+
+gsl_vector_complex *cvec_dot_c(gsl_vector_complex *v, complex double x) {
+  return cvec_dot_gslcplx(v, gsl_cplx_from_c99(x));
+}
+
+
+gsl_vector_complex *vec_dot_c(gsl_vector *v, complex double x) {
+  return vec_dot_gslcplx(v, gsl_cplx_from_c99(x));
+}
+
+
+complex double ddot(complex double x, complex double y) {
+  return x * y;
+}
+
+
+void gsl_vector_complex_print(gsl_vector_complex *v) {
+  for (size_t i = 0; i < v->size; i++) {
+    gsl_complex x = gsl_vector_complex_get(v, i);
+    printf("%4g + %4gi%c", GSL_REAL(x), GSL_IMAG(x), i < v->size-1 ? '\t' : '\n');
+  }
+}

21st_century_c/cplx.h

@@ -0,0 +1,31 @@
+#include <complex.h>
+#include <gsl/gsl_vector.h>
+
+
+
+gsl_vector_complex *cvec_dot_gslcplx(gsl_vector_complex *v, gsl_complex x);
+gsl_vector_complex *vec_dot_gslcplx(gsl_vector *v, gsl_complex x);
+gsl_vector_complex *cvec_dot_c(gsl_vector_complex *v, complex double x);
+gsl_vector_complex *vec_dot_c(gsl_vector *v, complex double x);
+void gsl_vector_complex_print(gsl_vector_complex *v);
+
+#define gsl_cplx_from_c99(x) (gsl_complex){.dat = {creal(x), cimag(x)}}
+
+complex double ddot(complex double x, complex double y);
+
+
+#define dot(x, y) _Generic((x),                                   \
+                    gsl_vector*         : dot_given_vec(y),       \
+                    gsl_vector_complex* : dot_given_cplx_vec(y),  \
+                    default             : ddot)                   \
+                    ((x), (y))
+
+
+#define dot_given_vec(y) _Generic ((y),                    \
+                           gsl_complex : vec_dot_gslcplx,  \
+                           default     : vec_dot_c)
+
+
+#define dot_given_cplx_vec(y) _Generic((y),                      \
+                                gsl_complex : cvec_dot_gslcplx,  \
+                                default     : cvec_dot_c)

21st_century_c/simple_cplx.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include "cplx.h"
+
+
+
+int main() {
+
+  int complex a = 1 + 2I;
+  complex double b = 2 + I;
+  gsl_complex c = gsl_cplx_from_c99(a);
+
+  gsl_vector *v = gsl_vector_alloc(8);
+  for (size_t i = 0; i < v->size; i++) {
+    gsl_vector_set(v, i, i/8.);
+  }
+
+  complex double adotb = dot(a, b);
+  printf("(1+2i) dot (2+i): %g+%gi\n", creal(adotb), cimag(adotb));
+
+  printf("v dot 2:\n");
+  double d = 2;
+  gsl_vector_complex_print(dot(v, d));
+
+  printf("v dot (1+2i)\n");
+  gsl_vector_complex *vc = dot(v, a);
+  gsl_vector_complex_print(vc);
+
+  printf("v dot (1+2i) again\n");
+  gsl_vector_complex_print(dot(v, c));
+
+}