@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
final int pl = post.length;
for (int p = 0; p < pl; p++) {
sb.append(LET).append(" (: post-group :) ").append(post[p]);
sb.append(' ').append(ASSIGN).append(' ').append(preExpr[p]).append(' ');
}
sb.append(GROUP).append(' ').append(BY);
final int sl = specs.length;
for (int s = 0; s < sl; s++) sb.append(s == 0 ? " " : SEP).append(specs[s]);
return sb.toString();
}
@Override
StringBuilder toString(final StringBuilder sb, final String ind) {
final int s = Integer.bitCount(used);
for (int i = 0, j = 0; i < s; i++, j++) {
while ((used & 1 << j) == 0) j++;
final int e = i == s - 1 ? 2 : 0;
sb.append(ind).append(ENDS[e]).append(String.format("%x", j)).append('\n');
kids[j].toString(sb, ind + ENDS[e + 1]);
}
return sb;
}