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coerce.spad
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coerce.spad
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)abbrev category TYPE Type
++ The new fundamental Type
++ Author: Richard Jenks
++ Date Created: 14 May 1992
++ Description: The fundamental Type;
Type() : Category == with ()
)abbrev category KOERCE CoercibleTo
++ Category for coerce
++ Author: Manuel Bronstein
++ Description:
++ A is coercible to B means any element of A can automatically be
++ converted into an element of B by the interpreter.
CoercibleTo(S : Type) : Category == with
coerce : % -> S
++ coerce(a) transforms a into an element of S.
)abbrev category KOERCEF CoercibleFrom
++ Category for coerce
++ Description:
++ A is coercible to B means any element of A can automatically be
++ converted into an element of B by the interpreter.
CoercibleFrom(S : Type) : Category == with
coerce : S -> %
++ coerce(a) transforms a into an element of %.
)abbrev category KONVERT ConvertibleTo
++ Category for convert
++ Author: Manuel Bronstein
++ Description:
++ A is convertible to B means any element of A
++ can be converted into an element of B,
++ but not automatically by the interpreter.
ConvertibleTo(S : Type) : Category == with
convert : % -> S
++ convert(a) transforms a into an element of S.
)abbrev category KONVERF ConvertibleFrom
++ Category for convert
++ Author: Manuel Bronstein
++ Description:
++ A is convertible to B means any element of A
++ can be converted into an element of B,
++ but not automatically by the interpreter.
ConvertibleFrom(S : Type) : Category == with
convert : S -> %
++ convert(a) transforms a into element of %.
)abbrev category RETRACT RetractableTo
++ Category for retract
++ Author: ???
++ Description:
++ A is retractable to B means that some elements of A can be converted
++ into elements of B and any element of B can be converted into an
++ element of A.
RetractableTo(S : Type) : Category == CoercibleFrom(S) with
retractIfCan : % -> Union(S,"failed")
++ retractIfCan(a) transforms a into an element of S if possible.
++ Returns "failed" if a cannot be made into an element of S.
retract : % -> S
++ retract(a) transforms a into an element of S if possible.
++ Error: if a cannot be made into an element of S.
add
retract(s) ==
(u := retractIfCan s) case "failed" => error "not retractable"
u
)abbrev category RETFROM RetractableFrom
++ Category for retract
++ Author: Johannes Grabmeier
++ Date Created: 25.09.2010
++ Description:
++ B is retractable from A means that some elements in A can be converted
++ into elements of B and any element of B can be converted into an
++ element of A.
RetractableFrom(S : Type) : Category == CoercibleTo(S) with
retractIfCan : S -> Union(%,"failed")
++ retractIfCan(a) transforms a into an element of % if possible.
++ Returns "failed" if a cannot be made into an element of %.
retract : S -> %
++ retract(a) transforms a into an element of % if possible.
++ Error: if a cannot be made into an element of %.
add
retract(s) ==
(u := retractIfCan s) case "failed" => error "not retractable"
u
--Copyright (c) 1991-2002, The Numerical ALgorithms Group Ltd.
--All rights reserved.
--
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--modification, are permitted provided that the following conditions are
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--
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-- distribution.
--
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--IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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