move difficulty-to-stdev logic to lib

1 files changed, 37 insertions, 1 deletions

diff --git a/comp.c b/comp.c
index 012eea1..6b4ec26 100644
--- a/comp.c
+++ b/comp.c
@@ -9,6 +9,42 @@
 
 double horizontal_stdev = 16, vertical_stdev = 16;
 
+#define NUM_DIFF_PRESETS (sizeof(DIFF_PRESETS) / sizeof(*DIFF_PRESETS))
+static struct { int diff; double stdev; } DIFF_PRESETS[] = {
+	{ 0, 66.80}, // 10
+	{ 8, 40.24}, // 20
+	{16, 28.14}, // 30
+	{24, 21.35}, // 40
+	{32, 17.20}, // 50
+	{40, 14.34}, // 60
+	{48, 12.15}, // 70
+	{56, 10.36}, // 80
+	{64,  8.83}, // 90
+	{72,  7.48}, // 100
+	{80,  6.32}, // 110
+	{88,  5.34}, // 120
+	{99,  0.00}, // 167
+};
+
+// optional function to set stdevs using precomputed 0-99 difficulty values.
+// fixed-step interpolation is done between presets.
+void comp_set_difficulty(int diff)
+{
+	if (diff < DIFF_PRESETS[0].diff)
+		diff = DIFF_PRESETS[0].diff;
+	else if (diff > DIFF_PRESETS[NUM_DIFF_PRESETS - 1].diff)
+		diff = DIFF_PRESETS[NUM_DIFF_PRESETS - 1].diff;
+
+	size_t ind = 1;
+	while (ind < NUM_DIFF_PRESETS - 1 && DIFF_PRESETS[ind].diff <= diff)
+		ind++;
+
+	double step = (DIFF_PRESETS[ind - 1].stdev - DIFF_PRESETS[ind].stdev) /
+		(DIFF_PRESETS[ind].diff - DIFF_PRESETS[ind - 1].diff);
+	horizontal_stdev = vertical_stdev = DIFF_PRESETS[ind - 1].stdev -
+		((diff - DIFF_PRESETS[ind - 1].diff) * step);
+}
+
 static double drand()
 {
 	return (double)rand() / RAND_MAX;
@@ -63,7 +99,7 @@ static struct pcoords throw_dart(struct pcoords target, struct ccoords *cc)
 	return cart_to_pol(*cc);
 }
 
-struct segment next_dart(int rem, int darts_in_hand)
+static struct segment next_dart(int rem, int darts_in_hand)
 {
 	char *c = NULL;
 	if (rem <= NUM_CHECKOUTS)