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\documentclass{article}
\usepackage{open-axiom}
\begin{document}
\title{src/algebra void.spad}
\author{Stephen M. Watt}
\maketitle
\begin{abstract}
\end{abstract}
\tableofcontents
\eject
These types act as the top and bottom of the type lattice
and are known to the compiler and interpreter for type resolution.
\section{domain VOID Void}
<<domain VOID Void>>=
)abbrev domain VOID Void
++ Author: Stephen M. Watt, Gabriel Dos Reis
++ Date Created: 1986
++ Date Last Updated: October 5, 2009
++ Basic Operations:
++ Related Domains: ErrorFunctions, ResolveLatticeCompletion, Exit
++ Also See:
++ AMS Classifications:
++ Keywords: type, mode, coerce, no value
++ Examples:
++ References:
++ Description:
++ This type is used when no value is needed, e.g., in the \spad{then}
++ part of a one armed \spad{if}.
++ All values can be coerced to type Void. Once a value has been coerced
++ to Void, it cannot be recovered.
Void: CoercibleTo OutputForm with
void: () -> % ++ void() produces a void object.
== add
void() == voidValue()$Foreign(Builtin)
coerce(v:%) == empty()$OutputForm
@
\section{domain EXIT Exit}
<<domain EXIT Exit>>=
import SetCategory
)abbrev domain EXIT Exit
++ Author: Stephen M. Watt
++ Date Created: 1986
++ Date Last Updated: May 30, 1991
++ Basic Operations:
++ Related Domains: ErrorFunctions, ResolveLatticeCompletion, Void
++ Also See:
++ AMS Classifications:
++ Keywords: exit, throw, error, non-local return
++ Examples:
++ References:
++ Description:
++ A function which does not return directly to its caller should
++ have Exit as its return type.
++
++ Note: It is convenient to have a formal \spad{coerce} into each type from
++ type Exit. This allows, for example, errors to be raised in
++ one half of a type-balanced \spad{if}.
Exit: SetCategory == add
coerce(n:%) == error "Cannot use an Exit value."
n1 = n2 == error "Cannot use an Exit value."
@
\section{package RESLATC ResolveLatticeCompletion}
<<package RESLATC ResolveLatticeCompletion>>=
import Void
import Exit
)abbrev package RESLATC ResolveLatticeCompletion
++ Author: Stephen M. Watt
++ Date Created: 1986
++ Date Last Updated: May 30, 1991
++ Basic Operations:
++ Related Domains: ErrorFunctions, Exit, Void
++ Also See:
++ AMS Classifications:
++ Keywords: mode, resolve, type lattice
++ Examples:
++ References:
++ Description:
++ This package provides coercions for the special types \spadtype{Exit}
++ and \spadtype{Void}.
ResolveLatticeCompletion(S: Type): with
coerce: S -> Void
++ coerce(s) throws all information about s away.
++ This coercion allows values of any type to appear
++ in contexts where they will not be used.
++ For example, it allows the resolution of different types in
++ the \spad{then} and \spad{else} branches when an \spad{if}
++ is in a context where the resulting value is not used.
coerce: Exit -> S
++ coerce(e) is never really evaluated. This coercion is
++ used for formal type correctness when a function will not
++ return directly to its caller.
== add
coerce(s: S): Void == void()
coerce(e: Exit): S ==
error "Bug: Should not be able to obtain value of type Exit"
@
\section{License}
<<license>>=
--Copyright (c) 1991-2002, The Numerical ALgorithms Group Ltd.
--All rights reserved.
--
--Redistribution and use in source and binary forms, with or without
--modification, are permitted provided that the following conditions are
--met:
--
-- - Redistributions of source code must retain the above copyright
-- notice, this list of conditions and the following disclaimer.
--
-- - Redistributions in binary form must reproduce the above copyright
-- notice, this list of conditions and the following disclaimer in
-- the documentation and/or other materials provided with the
-- distribution.
--
-- - Neither the name of The Numerical ALgorithms Group Ltd. nor the
-- names of its contributors may be used to endorse or promote products
-- derived from this software without specific prior written permission.
--
--THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
--IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
--TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
--PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
--OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
--EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
--PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
--PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
--LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
--NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
--SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
@
<<*>>=
<<license>>
<<domain VOID Void>>
<<domain EXIT Exit>>
<<package RESLATC ResolveLatticeCompletion>>
@
\eject
\begin{thebibliography}{99}
\bibitem{1} nothing
\end{thebibliography}
\end{document}
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