From: H.G.Muller <hgm@hgm-xboard.(none)>
Date: Fri, 3 Oct 2014 08:22:51 +0000 (+0200)
Subject: Use '2'-bit of range field to flag hop-friend
X-Git-Url: http://winboard.nl/cgi-bin?p=fairymax.git;a=commitdiff_plain;h=eaf83ea88d9567c38081aae39be668676edce3e2

Use '2'-bit of range field to flag hop-friend

The possibility to 'collide' from the hop platform by first stepping
back a number of squares before starting the second leg is now restricted
to one square, as indicated by the '1'-bit of the range field, for hoppers.
The '2' bit now flags that only a friendly piece can be used as platform;
an enemy counts as empty in the hop test, but because there is an actual
piece there it will terminate the ray (as no hop will reset that then).
---

diff --git a/fairymax.c b/fairymax.c
index 9b3adc7..470c03a 100644
--- a/fairymax.c
+++ b/fairymax.c
@@ -266,14 +266,14 @@ int k,q,l,e,E,z,n;      /* (q,l)=window, e=current eval. score, E=e.p. sqr.*/
        J=f;Z=g;
        if(h){h=0;goto A;}                      /* redo after doing old best*/
       }
-      s=t;v=r^flag>>12;                        /* capt & alternated vector */
+      s=t&&2&~rg|~t&16^k;v=r^flag>>12;         /* platform & toggled vector*/
       if(flag&15^4|u&32||                      /* no double or moved before*/
          p>2&!(flag&S)&&                       /* no P & no virgin jump,   */
          ((b[G=r<0?x&~15:BW-1|x&112]^32)<33    /* no virgin R in corner G, */
          ||b[G^1]|b[G^2]|b[FF=y+v-r])          /* no 2 empty sq. next to R */
         )t+=flag&4;                            /* fake capt. for nonsliding*/
       else if(flag&64)t=flag&128?0:t,flag&=63;else F=y; /* enable e.p.     */
-      if(s&&flag&8&&!(y-=rg*r,t=0)             /* hoppers go to next phase */
+      if(s&&flag&8&&!(y=rg&1?y-r:y,t=0)        /* hoppers go to next phase */
          ||!(flag&S)&&--rg<0)                  /* zig-zag piece? (w. delay)*/
        r=v,flag^=flag>>4&15;                   /* alternate vector & mode  */
      }W(!t);                                   /* if not capt. continue ray*/