ADD: main

src/field.h

 #ifndef _PHYSIQUE_H_
 #define _PHYSIQUE_H_
+
 #include "../utils/vec2/vec2.h"
 #include "../utils/gfx/gfx.h"
 #include "../utils/utils.h"
 #include <stdio.h>
 
-typedef struct _charge_t {
-	double q;
-	vec2 pos;
-} charge_t;
-
 // Compute E*qP/norm(qP)
 // Return false if norm(qP) < eps
 bool compute_e(charge_t c, vec2 p, double eps, vec2 *e);
@@ -22,11 +18,15 @@ bool compute_total_normalized_e(charge_t *charges, int num_charges, vec2 p, doub
 // starting from pos0.
 // Returns false if pos0 is not a valid position
 // (for example if pos0 is too close to a charge).
-static bool draw_field_line(struct gfx_context_t *ctxt, charge_t *charges, int num_charges, double dx, vec2 pos0, double x0, double x1, double y0, double y1);
+static bool
+draw_field_line(struct gfx_context_t *ctxt, charge_t *charges, int num_charges, double dx, vec2 pos0, double x0,
+				double x1, double y0, double y1);
 
 // Draw all the charges
 // A circle with minus sign for negative charges
 // A circle with a plus sign for positive charges
-static void draw_charges(struct gfx_context_t *context, charge_t *charges, int num_charges, double x0, double x1, double y0, double y1);
+static void
+draw_charges(struct gfx_context_t *context, charge_t *charges, int num_charges, double x0, double x1, double y0,
+			 double y1);
 
 #endif

src/main.c

 #include <stdlib.h>
+#include <time.h>
 #include "draw.h"
+#include "../utils/utils.h"
+
+#define SIDE_LEN 1000
+#define WID SIDE_LEN
+#define HEI WID
+#define NCHARGES 2
+#define DX 0.0005
+#define NPOINTS 32
 
 int main() {
+	srand(time(NULL));
+	charge_t charges[NCHARGES] = {
+			{.q=-0.25, .pos=vec2_create(0.25, 0.5)},
+			{.q=0.25, .pos=vec2_create(0.75, 0.5)},
+	};
+	struct gfx_context_t *ctxt = gfx_create("elec", WID, HEI);
+	draw_charges(ctxt, charges, NCHARGES, 0.0, 1.0, 0.0, 1.0);
+	for (int i = 0; i < NPOINTS; ++i) {
+		vec2 start = vec2_normalize(vec2_create(rand(), rand()));
+		draw_field_line(ctxt, charges, NCHARGES, DX, start, 0.0, 1.0, 0.0, 1.0);
+	}
+	while (gfx_keypressed() != SDLK_ESCAPE) gfx_present(ctxt);
+	gfx_destroy(ctxt);
 	return EXIT_SUCCESS;
 }