/**
* Constructs a new Decls with the specified head and tail.
*
* @requires head.size > 0 && tail.size > 0
* @ensures this.size' = head.size + tail.size && (all i: [0..head.size) | this.decls[i] =
* head.decls[i]) && (all i: [head.size..this.size') | this.decls[i] = tail.decls[i])
* @throws NullPointerException head = null || tail is null
*/
private Decls(Decls head, Decls tail) {
this.decls = new Decl[head.size() + tail.size()];
System.arraycopy(head.decls, 0, decls, 0, head.size());
System.arraycopy(tail.decls, 0, decls, head.size(), tail.size());
}
/**
* Returns the arity of this comprehension expression, which is the sum of the arities of declared
* variables
*
* @return #this.decls
*/
public int arity() {
return decls.size();
}