Denotational semantics is now used widely for the formal definition of programming languages but there is a lack of appropriate tools to support language development. General purpose language implementation systems are oriented to syntax with poor support for semantics. Specialised denotational semantics based systems correspond closely to the formalism but are rendered inflexible for language experimentation by their monolithic multiple stages Exploratory language development with formal definitions is better served by a unitary notation, encompassing syntax and semantics, which is close to but simpler than denotational semantics. Interactive implementation of the notation then facilitates language investigation through the direct execution of a formal definition as an interpreter for the defined language. This thesis presents Navel, a run-time typed, applicative order, pure functional programming language with integrated context free grammar rules. Navel has been used to develop prot...

syntax of Gull Figure 2. A Gull Program countdown and ML-Yacc. These programs are similar to the well-known Unix tools, enabling a system builder to handle complex languages. Since the purpose here is to study semantics, the central definition of syntax is the abstract syntax, and an associated concrete syntax is provided in such a way as to make the scanning and parsing simple. Although ML-Lex and ML-Yacc are used for the ML version, the Prolog version relies on a hand-built scanner and parser.

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