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A definite clause grammar (DCG) is a way of expressing grammar, either for natural or formal languages, in a logic programming language such as Prolog. It is closely related to the concept of attribute grammars / affix grammars. DCGs are usually associated with Prolog, but similar languages such as Mercury also include DCGs.
A simple parse tree. A parse tree is made up of nodes and branches. [4] In the picture the parse tree is the entire structure, starting from S and ending in each of the leaf nodes (John, ball, the, hit). In a parse tree, each node is either a root node, a branch node, or a leaf node. In the above example, S is a root node, NP and VP are branch ...
The Reed–Kellogg system was developed by Alonzo Reed and Brainerd Kellogg for teaching grammar to students through visualization. [1] It lost some support in the 1970s in the US, but has spread to Europe. [2] It is considered "traditional" in comparison to the parse trees of academic linguists. [3]
The phrase grammar of most programming languages can be specified using a Type-2 grammar, i.e., they are context-free grammars, [8] though the overall syntax is context-sensitive (due to variable declarations and nested scopes), hence Type-1. However, there are exceptions, and for some languages the phrase grammar is Type-0 (Turing-complete).
A simple tail recursive parser can be written much like a recursive descent parser. The typical algorithm for parsing a grammar like this using an abstract syntax tree is: Parse the next level of the grammar and get its output tree, designate it the first tree, F; While there is terminating token, T, that can be put as the parent of this node:
In practice, fully checking and completing the parsing of natural language corpora is a labour-intensive project that can take teams of graduate linguists several years. The level of annotation detail and the breadth of the linguistic sample determine the difficulty of the task and the length of time required to build a treebank.
Generalized phrase structure grammar (GPSG) is a framework for describing the syntax and semantics of natural languages. It is a type of constraint-based phrase structure grammar . Constraint based grammars are based around defining certain syntactic processes as ungrammatical for a given language and assuming everything not thus dismissed is ...
Formally, the reference context-free grammar of the language is ambiguous, meaning there is more than one correct parse tree. In many programming languages, one may write conditionally executed code in two forms: the if-then form, or the if-then-else form. (The else clause is optional.): if a then s if b then s1 else s2