This thesis presents a novel application of the technique known as proofs-as-programs.
Proofs-as-programs defines a correspondence between proofs in a constructive logic
and functional programs. By using this correspondence, a functional program may be
represented directly as the proof of a specification and so the program may be analysed within this proof framework. CʸNTHIA is a program editor for the functional
language ML which uses proofs-as-programs to analyse users' programs as they are
written. So that the user requires no knowledge of proof theory, the underlying proof
representation is completely hidden.
The proof framework allows programs written in CʸNTHIA to be checked to be
syntactically correct, well-typed, well-defined and terminating.
CʸNTHIA also embodies the idea of programming by analogy — rather than starting
from scratch, users always begin with an existing function definition. They then apply
a sequence of high-level editing commands which transform this starting definition into
the one required. These commands preserve correctness and also increase programming
efficiency by automating commonly occurring steps.
The design and implementation of CʸNTHIA is described and its role as a novice
programming environment is investigated. Use by experts is possible but only a sub-set of ML is currently supported. Two major trials of CʸNTHIA have shown that
CʸNTHIA is well-suited as a teaching tool. Users of CʸNTHIA make fewer programming errors and the feedback facilities of CʸNTHIA mean that it is easier to
track down the source of errors when they do occur
