... symbol.¹

By using this predicate for the remaining chain of the substitution node we prevent spurious ambiguities that would otherwise occur: adjoining at a node after or before a substitution results in the same derived tree. This parser never adjoins at substitution nodes: the same effect is obtained by adjoining at the root node of the tree to be substituted.

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... nodes.²

By using the predicate hc_na for the chain of the auxiliary tree we generally forbid adjunctions at foot nodes in order to prevent massive undesired ambiguities.

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... bound³

This is the case because one of the extreme positions E0,E is always the same as one of the resulting positions P0,P, as we are parsing either to the left or to the right from a given source. Therefore we have at most c ^. n⁷ instantiations.

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