When is a function a fold or an unfold?
نویسندگان
چکیده
We give a necessary and sufficient condition for when a set-theoretic function can be written using the recursion operator fold, and a dual condition for the recursion operator unfold. The conditions are simple, practically useful, and generic in the underlying datatype.
منابع مشابه
Constructively Characterizing Fold and Unfold
In this paper we formally state and prove theorems characterizing when a function can be constructively reformulated using the recursion operators fold and unfold, i.e. given a function h, when can a function g be constructed such that h = fold g or h = unfold g? These results are refinements of the classical characterization of fold and unfold given by Gibbons, Hutton and Altenkirch in [6]. Th...
متن کاملStreaming Algorithms (extended Abstract)
Unfolds generate data structures, and folds consume them. A hylomorphism is a fold after an unfold, generating then consuming a virtual data structure. A metamorphism is the opposite composition, an unfold after a fold; typically, it will convert from one data representation to another. In general, metamorphisms are less interesting than hylomorphisms: there is no automatic fusion to deforest t...
متن کاملTransformation of Left Terminating Programs: the Reordering Problem
A b s t r a c t . An Unfold/Fold transformation system is a source-to-source rewriting methodology devised to improve the efficiency of a program. Any such transformation should preserve the main properties of the initial program: among them, termination. When dealing with logic programs such as PROLOG programs, one is particularly interested in preserving left termination i.e. termination wrt ...
متن کاملFace Recognition using Eigenfaces , PCA and Supprot Vector Machines
This paper is based on a combination of the principal component analysis (PCA), eigenface and support vector machines. Using N-fold method and with respect to the value of N, any person’s face images are divided into two sections. As a result, vectors of training features and test features are obtain ed. Classification precision and accuracy was examined with three different types of kernel and...
متن کاملMore on Unfold/Fold Transformations of Normal Programs: Preservation of Fitting's Semantics
The unfold/fold transformation system defined by Tamaki and Sato was meant for definite programs. It transforms a program into an equivalent one in the sense of both the least tterbrand model semantics and the Computed Answer Substitution semantics. Seki extended the method to normal programs and specialized it in order to preserve also the finite failure set. The resulting system is correct wr...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Electr. Notes Theor. Comput. Sci.
دوره 44 شماره
صفحات -
تاریخ انتشار 2001