Segfault by running function twice

[Jeremy Cowgar]

I have created a function to compute the Levenshtein distance between
two strings, however, if I run it twice in the same application I get a
seg fault. You can call it on any combination of strings and it works,
but call it twice and you get a Segfault on the 2nd call of the
function. Can anyone look at this? I am not seeing an obvious problem in
the function but I certainly could be overlooking something.

Thanks! Jeremy

--------

Section Header

    + name := LEVENSHTEIN;

Section Private

    - levenshtein (s,t:ABSTRACT_STRING) :INTEGER <-
    // Compute the difference (edit distance) between two strings. The
distance
    // is the minimum number of edits necessary to transform `s` into
`t`. For
    // instance: Cat to Hat requires changing C to H, 1 edit. Dog to Mop
    // requires D to change to M, and g to change to p, 2 edits. Saturday to
    // Sunday delete "at" in Saturday (2 edits) and change the r to n
and you
    // have Sunday, 3 edits.
    (
        + n, m, a, b, c, cost : INTEGER;
        + d : FAST_ARRAY2[INTEGER];

        n := t.count + 1;
        m := s.count + 1;

        d := FAST_ARRAY2[INTEGER].create (m, n);

        0.to m do { i:INTEGER;
            d.put i to (i,0);
        };

        0.to n do { j:INTEGER;
            d.put j to (0,j);
        };

        1.to m do { i:INTEGER;
            1.to n do { j:INTEGER;
                ( (s.item i) = (t.item j)).if { cost := 0 } else { cost
:= 1 };
                a := d.item (i-1, j) + 1;
                b := d.item (i, j-1) + 1;
                c := d.item (i-1, j-1) + cost;

                d.put ((a.min b).min c) to (i,j);
            };
        };

        d.item (m,n)
    );

    - say_distance (a,b:ABSTRACT_STRING) <-
    (
        ("Distance between " + a + " and " + b + " is: " +
levenshtein(a,b).to_string + "\n").print;
    );

Section Public

    - main <-
    (
        //say_distance("Dog", "Mop"); // 2
        //say_distance("Cat", "Hat"); // 1
        say_distance("Saturday", "Sunday");  // 3
    );