Every application of the second rule doubles the depth of TEMP list (with respect to its length after the previous application of the rule).
the number of derivation steps for generating each È is always twice the number of steps for generating its predecessor, and for every sentential form of length Ê any partial derivation tree's depth is bounded by an exponential function of  The grammar of figure 2 is an © ¤ k grammar (viewing CAT as the category) but it does not satisfy the other constraints.