New puzzle! Or rather, new-ish, because this one has been lying around

[sgt/puzzles] / loopgen.h

diff --git a/loopgen.h b/loopgen.h
new file mode 100644 (file)
index 0000000..079c87c
--- /dev/null
+++ b/loopgen.h
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+/*
+ * loopgen.h: interface file for loop generation functions for grid.[ch].
+ */
+
+#ifndef _LOOPGEN_H
+#define _LOOPGEN_H
+
+#include "puzzles.h"
+#include "grid.h"
+
+enum face_colour { FACE_WHITE, FACE_GREY, FACE_BLACK };
+
+/* face should be of type grid_face* here. */
+#define FACE_COLOUR(face) \
+    ( (face) == NULL ? FACE_BLACK : \
+         board[(face) - g->faces] )
+
+typedef int (*loopgen_bias_fn_t)(void *ctx, char *board, int face);
+
+/* 'board' should be a char array whose length is the same as
+ * g->num_faces: this will be filled in with FACE_WHITE or FACE_BLACK
+ * after loop generation.
+ *
+ * If 'bias' is non-null, it should be a user-provided function which
+ * rates a half-finished board (i.e. may include some FACE_GREYs) for
+ * desirability; this will cause the loop generator to bias in favour
+ * of loops with a high return value from that function. The 'face'
+ * parameter to the bias function indicates which face of the grid has
+ * been modified since the last call; it is guaranteed that only one
+ * will have been (so that bias functions can work incrementally
+ * rather than re-scanning the whole grid on every call). */
+extern void generate_loop(grid *g, char *board, random_state *rs,
+                          loopgen_bias_fn_t bias, void *biasctx);
+
+#endif