refactoring: move produceexp into unit module, for want of a better one. add a bit of test coverage.

https://bugs.eressea.de/view.php?id=2137 - fix learning-by-doing with less than u->number people.

conf/e4/config.json

@@ -29,6 +29,7 @@
         "recruit.allow_merge": true,
         "study.expensivemigrants": true,
         "study.speedup": 2,
+        "study.from_use": 2,
         "world.era": 3,
         "rules.migrants.max": 0,
         "rules.reserve.twophase": true,

src/kernel/config.c

@@ -1599,16 +1599,6 @@ int maintenance_cost(const struct unit *u)
     return u_race(u)->maintenance * u->number;
 }
 
-int produceexp(struct unit *u, skill_t sk, int n)
-{
-    if (global.producexpchance > 0.0F) {
-        if (n == 0 || !playerrace(u_race(u)))
-            return 0;
-        learn_skill(u, sk, global.producexpchance);
-    }
-    return 0;
-}
-
 int lovar(double xpct_x2)
 {
     int n = (int)(xpct_x2 * 500) + 1;

src/kernel/unit.c

@@ -1933,3 +1933,22 @@ bool unit_name_equals_race(const unit *u) {
 bool unit_can_study(const unit *u) {
     return !((u_race(u)->flags & RCF_NOLEARN) || fval(u, UFL_WERE));
 }
+
+static double produceexp_chance(void) {
+    return global.producexpchance;
+}
+
+void produceexp_ex(struct unit *u, skill_t sk, int n, void(*learn)(unit *, skill_t, double))
+{
+    if (n != 0 && playerrace(u_race(u))) {
+        double chance = produceexp_chance();
+        if (chance > 0.0F) {
+            learn(u, sk, (n * chance) / u->number);
+        }
+    }
+}
+
+void produceexp(struct unit *u, skill_t sk, int n)
+{
+    produceexp_ex(u, sk, n, learn_skill);
+}

src/kernel/unit.h

@@ -161,8 +161,9 @@ extern "C" {
     struct skill *unit_skill(const struct unit *u, skill_t id);
     bool has_skill(const unit * u, skill_t sk);
     int effskill(const struct unit *u, skill_t sk, const struct region *r);
-    int produceexp(struct unit *u, skill_t sk, int n);
     int SkillCap(skill_t sk);
+    void produceexp(struct unit *u, skill_t sk, int n);
+    void produceexp_ex(struct unit *u, skill_t sk, int n, void(*learn)(unit *, skill_t, double));
 
     void set_level(struct unit *u, skill_t id, int level);
     int get_level(const struct unit *u, skill_t id);

src/kernel/unit.test.c

@@ -350,6 +350,30 @@ static void test_age_familiar(CuTest *tc) {
     test_cleanup();
 }
 
+static CuTest *g_tc;
+
+static void cb_learn_one(unit *u, skill_t sk, double chance) {
+    CuAssertIntEquals(g_tc, SK_ALCHEMY, sk);
+    CuAssertDblEquals(g_tc, global.producexpchance / u->number, chance, 0.01);
+}
+
+static void cb_learn_two(unit *u, skill_t sk, double chance) {
+    CuAssertIntEquals(g_tc, SK_ALCHEMY, sk);
+    CuAssertDblEquals(g_tc, 2 * global.producexpchance / u->number, chance, 0.01);
+}
+
+static void test_produceexp(CuTest *tc) {
+    unit *u;
+
+    g_tc = tc;
+    test_cleanup();
+    u = test_create_unit(test_create_faction(0), test_create_region(0, 0, 0));
+    global.producexpchance = 1.0;
+    produceexp_ex(u, SK_ALCHEMY, 1, cb_learn_one);
+    produceexp_ex(u, SK_ALCHEMY, 2, cb_learn_two);
+    test_cleanup();
+}
+
 CuSuite *get_unit_suite(void)
 {
     CuSuite *suite = CuSuiteNew();
@@ -368,5 +392,6 @@ CuSuite *get_unit_suite(void)
     SUITE_ADD_TEST(suite, test_skill_hunger);
     SUITE_ADD_TEST(suite, test_skill_familiar);
     SUITE_ADD_TEST(suite, test_age_familiar);
+    SUITE_ADD_TEST(suite, test_produceexp);
     return suite;
 }