# between

The`between`

filter consists of the single word `between`

followed by two
set filters enclosed in parentheses:
between-filter:= 'between' '('set-filter1set-filter2')'set-filter1:=set-filterset-filter2:=set-filter

The `between`

filter represents squares that are between some line segment (horizontal, vertical or diagonal) whose endpoints are in *set-filter1* and *set-filter2*.

More formally, the `between`

filter is a set filter whose associated set in a position is the set of squares between the sets associated to *set-filter1* and *set-filter2*. That is, square *s* is a member of the set associated with a `between`

filter in a position if there are squares *t1, t2* in the sets associated with *set-filter1, setfilter2* respectively such that *s* is between *t1* and *t2*. A square *s* is *between squares t1 and t2* if

*s*is neither*t1*nor*t2*- There is basic direction
*d*such that, beginning at square*t1*and traversing a path of squares in the direction*d*, the square*s*will be traversed.

`between (K h1-8)`

= [f1,g1,f2,g3]

Of the h-file squares, only e1-h1 and e1-h4 form a line (direction).

Only the squares `between`

the endpoints of each line are part of the set.

D. Hlebec

1/2 prize, Berger 170 MT

2015

piece $x in [Aa] piece $y in [Aa] countsquares 6 [Aa] on between ($x $y)

This matches any line, orthogonal or diagonal, that has 8 pieces. One of the matches is the stalemate above.

Examples