adde Makefile

tortoise/Makefile

@@ -0,0 +1,20 @@
+# Basic Makefile for the tortoise package.
+
+CFLAGS =
+LIBS =
+
+.PHONY: clean build run
+
+build: tortoise
+
+clean:
+	rm -f tortoise tortoise.o
+
+run: tortoise
+	./tortoise
+
+tortoise: tortoise.o
+	gcc $< -o $@ $(LIBS)
+
+tortoise.o: tortoise.c
+	gcc -c $< -o $@ $(CFLAGS)

tortoise/core.c

@@ -1,45 +0,0 @@
-/* Simple backend for a Logo like tortoise drawer. */
-
-#include <stdlib.h>
-#include <stdio.h>
-#include <unistd.h>
-
-static const int WIDTH = 10;
-static const int HEIGHT = 10;
-
-static FILE*
-start_gnuplot() {
-  FILE* output;
-  int pipes[2];
-  pid_t pid;
-
-  pipe(pipes);
-  pid = fork();
-
-  if (!pid) {
-    dup2 (pipes[0], STDIN_FILENO);
-    execlp ("gnuplot", NULL);
-    return; /* Not reached. */
-  }
-
-  output = fdopen(pipes[1], "w");
-
-  fprintf (output, "set multiplot\n");
-  fprintf (output, "set parametric\n");
-  fprintf (output, "set xrange [-%d:%d]\n", WIDTH, WIDTH);
-  fprintf (output, "set yrange [-%d:%d]\n", HEIGHT, HEIGHT);
-  fprintf (output, "set size ratio -1\n");
-  fprintf (output, "unset xtics\n");
-  fprintf (output, "unset ytics\n");
-  fflush (output);
-
-  return output;
- }
-
-static FILE* global_output;
-
-int main(int argc, char *argv[]) {
-  global_output = start_gnuplot();
-
-  return EXIT_SUCCESS;
-}

tortoise/tortoise.c

@@ -3,9 +3,14 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <math.h>
 
 static const int WIDTH = 10;
 static const int HEIGHT = 10;
+static double x, y;
+static double direction;
+static int pendown;
+
 
 static FILE*
 start_gnuplot() {
@@ -38,8 +43,46 @@ start_gnuplot() {
 
 static FILE* global_output;
 
+static void tortoise_reset () {
+  x = y = 0.0;
+  direction = 0.0;
+  pendown = 1;
+
+  fprintf(global_output, "clear\n");
+  fflush(global_output);
+}
+
+
 int main(int argc, char *argv[]) {
   global_output = start_gnuplot();
-
+  tortoise_reset ();
   return EXIT_SUCCESS;
 }
+
+static void draw_line(FILE *output, double x1, double y1, double x2,
+                      double y2) {
+  fprintf(output, "plot [0:1] %f + %f * t, %f + %f * t notitle\n",
+	  x1, x2 -x1, y1, y2 -y1);
+  fflush(output);
+}
+
+static void tortoise_pendown() {
+  pendown = 1;
+}
+
+static void tortoise_penup() {
+  pendown = 0;
+}
+
+static void tortoise_move(double length) {
+  double newX, newY;
+
+  newX = x + length * cos (direction);
+  newY = y + length * sin (direction);
+
+  if (pendown)
+    draw_line(global_output, x, y, newX, newY);
+
+  x = newX;
+  y = newY;
+}