produceexp uses a json-configurable constant

make get_param_flt return a double, floats are for wimps.

src/battle.c

@@ -2895,10 +2895,10 @@ static void aftermath(battle * b)
                 if (sh && fval(sh, SF_DAMAGED)) {
                     int n = b->turn - 2;
                     if (n > 0) {
-                        float dmg =
+                        double dmg =
                             get_param_flt(global.parameters, "rules.ship.damage.battleround",
                             0.05F);
-                        damage_ship(sh, dmg * (float)n);
+                        damage_ship(sh, dmg * n);
                         freset(sh, SF_DAMAGED);
                     }
                 }

src/chaos.c

@@ -191,7 +191,7 @@ static void chaos(region * r)
 
                         while (sh) {
                             ship *nsh = sh->next;
-                            float dmg =
+                            double dmg =
                                 get_param_flt(global.parameters, "rules.ship.damage.atlantis",
                                 0.50);
                             damage_ship(sh, dmg);

src/kernel/config.c

@@ -1123,10 +1123,10 @@ void set_basepath(const char *path)
     g_basedir = path;
 }
 
-float get_param_flt(const struct param *p, const char *key, float def)
+double get_param_flt(const struct param *p, const char *key, double def)
 {
     const char *str = get_param(p, key);
-    return str ? (float)atof(str) : def;
+    return str ? atof(str) : def;
 }
 
 void set_param(struct param **p, const char *key, const char *data)

src/kernel/config.h

@@ -284,7 +284,7 @@ extern "C" {
     const char *get_param(const struct param *p, const char *key);
     int get_param_int(const struct param *p, const char *key, int def);
     int check_param(const struct param *p, const char *key, const char *searchvalue);
-    float get_param_flt(const struct param *p, const char *key, float def);
+    double get_param_flt(const struct param *p, const char *key, double def);
     void free_params(struct param **pp);
 
     bool ExpensiveMigrants(void);

src/kernel/unit.c

@@ -1935,7 +1935,7 @@ bool unit_can_study(const unit *u) {
 }
 
 static double produceexp_chance(void) {
-    return global.producexpchance;
+    return get_param_flt(global.parameters, "study.from_use", 1.0 / 3);
 }
 
 void produceexp_ex(struct unit *u, skill_t sk, int n, bool (*learn)(unit *, skill_t, double))

src/kernel/unit.test.c

@@ -354,13 +354,13 @@ static CuTest *g_tc;
 
 static bool 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);
+    CuAssertDblEquals(g_tc, 0.5 / u->number, chance, 0.01);
     return false;
 }
 
 static bool 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);
+    CuAssertDblEquals(g_tc, 2 * 0.5 / u->number, chance, 0.01);
     return false;
 }
 
@@ -370,7 +370,7 @@ static void test_produceexp(CuTest *tc) {
     g_tc = tc;
     test_cleanup();
     u = test_create_unit(test_create_faction(0), test_create_region(0, 0, 0));
-    global.producexpchance = 1.0;
+    set_param(&global.parameters, "study.from_use", "0.5");
     produceexp_ex(u, SK_ALCHEMY, 1, cb_learn_one);
     produceexp_ex(u, SK_ALCHEMY, 2, cb_learn_two);
     test_cleanup();

src/laws.c

@@ -2762,14 +2762,14 @@ void sinkships(struct region * r)
             if (fval(r->terrain, SEA_REGION)) {
                 if (!enoughsailors(sh, crew_skill(sh))) {
                     // ship is at sea, but not enough people to control it
-                    float dmg = get_param_flt(global.parameters,
+                    double dmg = get_param_flt(global.parameters,
                         "rules.ship.damage.nocrewocean",
                         0.30F);
                     damage_ship(sh, dmg);
                 }
             } else if (!ship_owner(sh)) {
                 // any ship lying around without an owner slowly rots
-                float dmg = get_param_flt(global.parameters, "rules.ship.damage.nocrew", 0.05F);
+                double dmg = get_param_flt(global.parameters, "rules.ship.damage.nocrew", 0.05F);
                 damage_ship(sh, dmg);
             }
         }
@@ -3496,7 +3496,7 @@ static int use_item(unit * u, const item_type * itype, int amount, struct order
 
 static double heal_factor(const unit * u)
 {
-    static float elf_regen = -1;
+    static double elf_regen = -1;
     switch (old_race(u_race(u))) {
     case RC_TROLL:
     case RC_DAEMON:

src/monsters.c

@@ -80,7 +80,7 @@ static void give_peasants(unit *u, const item_type *itype, int reduce) {
     unit_addorder(u, parse_order(buf, u->faction->locale));
 }
 
-static float monster_attack_chance(void) {
+static double monster_attack_chance(void) {
     return get_param_flt(global.parameters, "rules.monsters.attack_chance", 0.4f);
 }
 

src/move.c

@@ -704,7 +704,7 @@ static float damage_drift(void)
 {
     static float value = -1.0F;
     if (value < 0) {
-        value = get_param_flt(global.parameters, "rules.ship.damage_drift", 0.02F);
+        value = (float)get_param_flt(global.parameters, "rules.ship.damage_drift", 0.02F);
     }
     return value;
 }
@@ -1955,7 +1955,7 @@ sail(unit * u, order * ord, bool move_on_land, region_list ** routep)
                     ADDMSG(&f->msgs, msg_message("sailnolandingstorm", "ship region", sh, next_point));
                 }
                 else {
-                    float dmg =
+                    double dmg =
                         get_param_flt(global.parameters, "rules.ship.damage.nolanding",
                         0.10F);
                     ADDMSG(&f->msgs, msg_message("sailnolanding", "ship region", sh,

src/randenc.c

@@ -746,7 +746,7 @@ static void move_iceberg(region * r)
 
             for (sh = r->ships; sh; sh = sh->next) {
                 /* Meldung an Kapitän */
-                float dmg =
+                double dmg =
                     get_param_flt(global.parameters, "rules.ship.damage.intoiceberg",
                     0.10F);
                 damage_ship(sh, dmg);
@@ -759,7 +759,7 @@ static void move_iceberg(region * r)
                 translist(&rc->buildings, &r->buildings, rc->buildings);
             }
             while (rc->ships) {
-                float dmg =
+                double dmg =
                     get_param_flt(global.parameters, "rules.ship.damage.withiceberg",
                     0.10F);
                 fset(rc->ships, SF_SELECT);
@@ -893,7 +893,7 @@ static void godcurse(void)
                 ship *sh;
                 for (sh = r->ships; sh;) {
                     ship *shn = sh->next;
-                    float dmg =
+                    double dmg =
                         get_param_flt(global.parameters, "rules.ship.damage.godcurse",
                         0.10F);
                     damage_ship(sh, dmg);