New option RAILWAYS

With RAILWAYS, highway-like sectors double as rail.  They need to be
at least 5% efficient to be operational, and then they additionally
extend rail into adjacent sectors that are at least 60% efficient.

New opt_RAILWAYS, SCT_HAS_RAIL(), sct_rail_track().  Update
sector_mcost(), bp_neighbors(), lnd_mar_one_sector() for RAILWAYS
mobility rules.  Update sinfra(), spyline(), satdisp_sect() to show
rail track instead of rail infrastructure for RAILWAYS.

New virtual sector selector track, implemented by nsc_sct_track().

include/econfig-spec.h

@@ -177,6 +177,8 @@ EMPCF_OPT("NO_PLAGUE", opt_NO_PLAGUE,
     "Disable plague")
 EMPCF_OPT("PINPOINTMISSILE", opt_PINPOINTMISSILE,
     "Enable marine missiles")
+EMPCF_OPT("RAILWAYS", opt_RAILWAYS,
+    "Highways double as rail")
 EMPCF_OPT("RES_POP", opt_RES_POP,
     "Population is limited by research")
 EMPCF_OPT("SAIL", opt_SAIL,

include/sect.h

@@ -183,6 +183,11 @@ extern struct dchrstr bigcity_dchr;
 
 #define FORTEFF 5		/* forts must be 5% efficient to fire. */
 
+/* Can trains enter sector SP? */
+#define SCT_HAS_RAIL(sp)					\
+    (opt_RAILWAYS ? sct_rail_track((sp)) != 0			\
+     : intrchr[INT_RAIL].in_enable && (sp)->sct_rail != 0)
+
 #define MOB_MOVE    0
 #define MOB_MARCH   1
 #define MOB_RAIL    2
@@ -218,5 +223,6 @@ struct sctintrins {
 extern struct sctintrins intrchr[INT_DEF + 2];
 
 extern int fort_fire(struct sctstr *);
+extern int sct_rail_track(struct sctstr *);
 
 #endif

info/Options.t

@@ -41,6 +41,7 @@ MARKET:         Time-delay market and trade.
 LOANS:          Allows S&L type interaction between countries.
 LANDSPIES:      Creates land unit style spies.
 NO_FORT_FIRE:   Forts cannot fire.
+RAILWAYS	Highways double as rail
 TECH_POP:       Technology costs more to make as your civilian population
                  grows past 50,000 civilians.
 TREATIES:       Sign treaties with your friends and enemies, and breaking of

info/Railroad.t

@@ -0,0 +1,27 @@
+.TH Concept "Railroad"
+.NA Railroad "How railroads work"
+.LV Expert
+Trains are land units with capability \*Qtrain\*U.  They can't be
+loaded on land units, but they can be loaded on ships, subject to the
+usual restrictions for non-light and heavy land units.
+.s1
+Unlike other units, trains can enter a sector only if it has
+(operational) railroad track.
+.s1
+If option RAILWAYS is disabled, a sector has railroad track as long as
+its rail infrastructure efficiency is non-zero.  Train mobility cost
+depends on rail infrastructure efficiency (see \*Qinfo Mobility\*U).
+Spy and satellite reports show approximate rail infrastructure
+efficiency in column \*Qrl eff\*U.
+.s1
+If option RAILWAYS is enabled, all highway-like sectors are railways,
+and the track is operational as long as the sector is at least 5%
+efficient.  A sector is highway-like if its mobility cost at 100% is
+zero (column mob cost in \*Qshow sect s\*u).  Operational railways
+additionally extend track into adjacent sectors that are at least 60%
+efficient and owned by the same nation.  Sector selector track gives
+the number of operational railways within one sector range.  Spy and
+satellite reports show the presence of track in column \*Qrl eff\*U.
+To visualize your railway network, try \*Qsect # ?track#0\*U.
+.s1
+.SA "LandUnits"

info/Unit-types.t

@@ -193,6 +193,7 @@ the unit can fire 'general unit flak' (see "info Flak")
 the unit is a spy
 .L train
 the unit is a train, and can't be loaded on land units
+(see "info Railroad")
 .L heavy
 the unit cannot be carried on land units or ships, not even supply ships
 .in
@@ -235,4 +236,3 @@ marines 1                  5f 10s xlight light marine
 .FI
 .s1
 .SA "land, LandUnits"
-

src/lib/commands/sinf.c

@@ -73,6 +73,9 @@ sinfra(void)
 	pr("%4d%% ", sect.sct_effic);
 	pr("%4d%% ", sect.sct_road);
 	prmobcost(&sect, MOB_MOVE);
+	if (opt_RAILWAYS)
+	    pr(sct_rail_track(&sect) ? "  yes " : "   no ");
+	else
 	    pr("%4d%% ", sect.sct_rail);
 	prmobcost(&sect, MOB_RAIL);
 	pr("%4d%% ", SCT_DEFENSE(&sect));

src/lib/commands/spy.c

@@ -189,7 +189,7 @@ spy_report(struct sctstr *sp)
        sp->sct_oldown,
        roundintby((int)sp->sct_effic, 10),
        roundintby((int)sp->sct_road, 10),
-       roundintby((int)sp->sct_rail, 10),
+       opt_RAILWAYS ? !!sct_rail_track(sp) : roundintby(sp->sct_rail, 10),
        roundintby((int)sp->sct_defense, 10),
        roundintby(sp->sct_item[I_CIVIL], 10),
        roundintby(sp->sct_item[I_MILIT], 10),

src/lib/common/move.c

@@ -33,8 +33,10 @@
 
 #include <config.h>
 
+#include "file.h"
 #include "misc.h"
 #include "nat.h"
+#include "optlist.h"
 #include "path.h"
 #include "sect.h"
 #include "xy.h"
@@ -48,6 +50,12 @@ sector_mcost(struct sctstr *sp, int mobtype)
     if (base < 0)
 	return -1.0;
 
+    if (mobtype == MOB_RAIL && opt_RAILWAYS) {
+	if (!SCT_HAS_RAIL(sp))
+	    return -1;
+	mobtype = MOB_MARCH;
+    }
+
     /* linear function in eff, d_mob0 at 0%, d_mob1 at 100% */
     base += (dchr[sp->sct_type].d_mob1 - base) * sp->sct_effic / 100;
     if (CANT_HAPPEN(base < 0))
@@ -83,3 +91,33 @@ speed_factor(double effspd, int tech)
 {
     return 480.0 / (effspd + techfact(tech, effspd));
 }
+
+/* Minimal efficiency for railway and railway extension (opt_RAILWAYS) */
+#define SCT_RAIL_EFF 5
+#define SCT_RAIL_EXT_EFF 60
+
+/* Is sector SP a railway? */
+#define SCT_IS_RAILWAY(sp) \
+    (dchr[(sp)->sct_type].d_mob1 == 0 && (sp)->sct_effic >= SCT_RAIL_EFF)
+/* May sector SP have a railway extension? */
+#define SCT_MAY_HAVE_RAIL_EXT(sp) \
+    ((sp)->sct_effic >= SCT_RAIL_EXT_EFF)
+/* Does railway sector SP extend railway track into sector TOSP? */
+#define SCT_EXTENDS_RAIL(sp, tosp) \
+    ((sp)->sct_own == (tosp)->sct_own && SCT_MAY_HAVE_RAIL_EXT(tosp))
+
+int
+sct_rail_track(struct sctstr *sp)
+{
+    int i, res;
+    struct sctstr *nsp;
+
+    res = !!SCT_IS_RAILWAY(sp);
+    for (i = DIR_FIRST; i <= DIR_LAST; i++) {
+	nsp = getsectp(sp->sct_x + diroff[i][0],
+		       sp->sct_y + diroff[i][1]);
+	if (SCT_IS_RAILWAY(nsp) && SCT_EXTENDS_RAIL(nsp, sp))
+	    res++;
+    }
+    return res;
+}

src/lib/common/nsc.c

@@ -49,6 +49,7 @@
 static void *nsc_ver(struct valstr *, struct natstr *, void *);
 static void *nsc_ver_maxnoc(struct valstr *, struct natstr *, void *);
 static void *nsc_sct_terr(struct valstr *, struct natstr *, void *);
+static void *nsc_sct_track(struct valstr *, struct natstr *, void *);
 static void *nsc_cargo_nplane(struct valstr *, struct natstr *, void *);
 static void *nsc_cargo_nchopper(struct valstr *, struct natstr *, void *);
 static void *nsc_cargo_nxlight(struct valstr *, struct natstr *, void *);
@@ -160,6 +161,7 @@ struct castr sect_ca[] = {
     {"uran", fldoff(sct_uran), NSC_UCHAR, 0, NULL, EF_BAD, 0},
     {"oldown", fldoff(sct_oldown), NSC_NATID, 0, NULL, EF_NATION, 0},
     {"off", fldoff(sct_off), NSC_UCHAR, 0, NULL, EF_BAD, 0},
+    {"track", 0, NSC_LONG, 0, nsc_sct_track, EF_BAD, NSC_EXTRA},
     NSC_IVEC(fldoff(sct_item), ""),
     NSC_IVEC(fldoff(sct_dist), "_dist"),
     NSC_IVEC(fldoff(sct_del), "_del"),
@@ -772,6 +774,13 @@ nsc_sct_terr(struct valstr *val, struct natstr *np, void *ptr)
     return ptr;
 }
 
+static void *
+nsc_sct_track(struct valstr *val, struct natstr *np, void *ptr)
+{
+    val->val_as.lng = sct_rail_track(ptr);
+    return NULL;
+}
+
 static void *
 nsc_cargo_nplane(struct valstr *val, struct natstr *np, void *ptr)
 {

src/lib/common/path.c

@@ -218,8 +218,7 @@ bp_neighbors(struct as_coord c, struct as_coord *cp, void *pp)
 	   move through it.  We calculate it later. */
 	if (dchr[sp->sct_type].d_mob0 < 0)
 	    continue;
-	if (bp->bp_mobtype == MOB_RAIL
+	if (bp->bp_mobtype == MOB_RAIL && !SCT_HAS_RAIL(sp))
-	    && (!intrchr[INT_RAIL].in_enable || sp->sct_rail == 0))
 	    continue;
 	if (sp->sct_own != from->sct_own)
 	    continue;

src/lib/global/options.c

@@ -57,6 +57,7 @@ int opt_NOMOBCOST = 1;
 int opt_NO_FORT_FIRE = 0;
 int opt_NO_PLAGUE = 1;
 int opt_PINPOINTMISSILE = 1;
+int opt_RAILWAYS = 0;
 int opt_RES_POP = 0;
 int opt_SAIL = 1;
 int opt_SLOW_WAR = 0;

src/lib/subs/lndsub.c

@@ -915,7 +915,7 @@ lnd_mar_one_sector(struct emp_qelem *list, int dir, natid actor,
 		continue;
 	    }
 	}
-	if ((!intrchr[INT_RAIL].in_enable || sect.sct_rail == 0)
+	if (!SCT_HAS_RAIL(&sect)
 	    && lnd_mobtype(&llp->unit.land) == MOB_RAIL) {
 	    if (together) {
 		pr("no rail system in %s\n", xyas(newx, newy, actor));

src/lib/subs/satmap.c

@@ -265,7 +265,7 @@ satdisp_sect(struct sctstr *sp, int acc)
        dchr[sp->sct_type].d_mnem,
        sp->sct_own, roundintby((int)sp->sct_effic, acc / 2),
        roundintby((int)sp->sct_road, acc / 2),
-       roundintby((int)sp->sct_rail, acc / 2),
+       opt_RAILWAYS ? !!sct_rail_track(sp) : roundintby(sp->sct_rail, acc / 2),
        roundintby((int)sp->sct_defense, acc / 2),
        roundintby(sp->sct_item[I_CIVIL], acc),
        roundintby(sp->sct_item[I_MILIT], acc),