Prior work on combining language modeling and unsupervised tree learning typically embed soft, tree-like structures as hidden layers of a deep network (Cho et al., 2014;Chung et al., 2017;Shen et al., 2018Shen et al., , 2019.
buys and blunsom (2018) make Markov assumptions and perform exact marginalization over latent dependency 22 Many prior works that induce trees directly from words often employ additional heuristics based on punctuation (Seginer, 2007;Ponvert et al., 2011;Spitkovsky et al., 2013;Parikh et al., 2014), as punctuation (e.g.