1 files changed, 37 insertions, 0 deletions
diff --git a/pop.c b/pop.c
new file mode 100644
index 0000000..99ed3d1
--- /dev/null
+++ b/pop.c
@@ -0,0 +1,37 @@
+#include "prv.h"
+#include <stdlib.h>
+
+int pop(const struct lex *l, struct prv *p)
+{
+    size_t n;
+    struct pos *npos = NULL;
+
+    if (!p->n)
+    {
+        fprintf(stderr, "%s: underflow\n", __func__);
+        return -1;
+    }
+    else if (!(n = p->n - 1))
+    {
+        free(p->pos);
+        p->pos = NULL;
+    }
+    else if (!(npos = realloc(p->pos, n * sizeof *npos)))
+    {
+        perror("realloc(3)");
+        return -1;
+    }
+
+    p->pos = npos;
+    p->n = n;
+
+    if (p->n)
+    {
+        const struct pos *old = &p->pos[--p->i];
+
+        if (old->seq->end && old->seq->end(l, p))
+            return -1;
+    }
+
+    return 0;
+}