A-M baby

Task/Generator-Exponential/C/generator-exponential-2.c

@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+typedef int (*seq_func)(void *);
+#define SEQ_BASE seq_func f; int output
+
+/* sort of polymorphing data structure */
+typedef struct { SEQ_BASE; } gen_t;
+
+int seq_next(void *state)
+{
+	return ((gen_t*)state)->output = (*(seq_func*)state)(state);
+}
+
+typedef struct {
+	SEQ_BASE;
+	int pos, n;
+} power_gen_t;
+
+int power_next(void *s)
+{
+	return (int)pow(++((power_gen_t*)s)->pos, ((power_gen_t*)s)->n);
+}
+
+void *power_seq(int n)
+{
+	power_gen_t *s = malloc(sizeof(power_gen_t));
+	s->output = -1;
+	s->f = power_next;
+	s->n = n;
+	s->pos = -1;
+	return s;
+}
+
+typedef struct {
+	SEQ_BASE;
+	void *in, *without;
+} filter_gen_t;
+
+int filter_next(void *s)
+{
+	gen_t *in = ((filter_gen_t*)s)->in, *wo = ((filter_gen_t*)s)->without;
+
+	do{
+		seq_next(in);
+		while (wo->output < in->output)
+			seq_next(wo);
+	} while(wo->output == in->output);
+
+	return in->output;
+}
+
+void* filter_seq(gen_t *in, gen_t *without)
+{
+	filter_gen_t *filt = malloc(sizeof(filter_gen_t));
+	filt->in = in;
+	filt->without = without;
+	filt->f = filter_next;
+	filt->output = -1;
+	return filt;
+}
+
+int main()
+{
+	int i;
+	void *s = filter_seq(power_seq(2), power_seq(3));
+
+	for (i = 0; i < 20; i++) seq_next(s);
+	for (i = 0; i < 10; i++)
+		printf("%d\n", seq_next(s));
+
+	return 0;
+}