<ManSection>
<Filt Arg="arg" Name="IsDerivedMethod" Label="for IsAttributeStoringRep"/>
<Returns><K>true</K> or <K>false</K>
</Returns>
<Description>
A derivation object describes a derived method.
It contains information about which operation the derived method
implements, and which other operations it relies on.
</Description>
</ManSection>
<ManSection>
<Func Arg="target_op_name, description, used_ops_with_multiples, func, weight, category_filter, loop_multiplier, category_getters" Name="CreateDerivation" />
<Description>
Creates a new derivation object.
The argument <A>target_op_name</A> is the name of the operation which
the derived method implements.
The argument <A>description</A> should describe the derivation.
The argument <A>used_ops_with_multiples</A> contains
<P/>
<List>
<Item>
the name of each operation used by the derived method,
</Item>
<Item>
together with a positive integer specifying how many times that operation is used and
</Item>
<Item>
either a category getter or <C>fail</C>.
</Item>
</List>
<P/>
This is given as a list of lists, where each sublist has as
first entry the name of an operation, as second entry an integer and as
third entry either a function or <C>fail</C>. This function should accept the
category for which this derivation will be installed,
and return a category for which the operation in the first
entry must be installed for the derivation to be considered applicable.
The argument <A>func</A> contains the actual implementation of the
derived method.
The argument <A>weight</A> is an additional number to add
when calculating the resulting weight of the target operation
using this derivation. Unless there is any particular reason
to regard the derivation as exceedingly expensive, this number
should be <C>1</C>.
The argument <A>category_filter</A> is a filter (or function) describing
which categories the derivation is valid for. If it is valid
for all categories, then this argument should have the value
<C>IsCapCategory</C>. The output of <A>category_filter</A> must not
change during the installation of operations. In particular, it must
not rely on <Code>CanCompute</Code> to check conditions.
</Description>
</ManSection>
<ManSection>
<Attr Arg="d" Name="Description" Label="for IsDerivedMethod"/>
<Description>
A description of the derivation.
</Description>
</ManSection>
<ManSection>
<Attr Arg="d" Name="AdditionalWeight" Label="for IsDerivedMethod"/>
<Description>
Additional weight for the derivation.
</Description>
</ManSection>
<ManSection>
<Attr Arg="d" Name="DerivationFunction" Label="for IsDerivedMethod"/>
<Description>
The implementation of the derivation.
</Description>
</ManSection>
<ManSection>
<Attr Arg="d" Name="CategoryFilter" Label="for IsDerivedMethod"/>
<Description>
Filter describing which categories the derivation is valid for.
</Description>
</ManSection>
<ManSection>
<Oper Arg="d, C" Name="IsApplicableToCategory" Label="for IsDerivedMethod, IsCapCategory"/>
<Returns><C>true</C> if the category <A>C</A> is known to satisfy the category filter of the derivation <A>d</A>.
</Returns>
<Description>
Checks if the derivation is known to be valid for a given category.
</Description>
</ManSection>
<ManSection>
<Attr Arg="d" Name="TargetOperation" Label="for IsDerivedMethod"/>
<Returns> The name (as a string) of the operation implemented
by the derivation <A>d</A>
</Returns>
<Description>
<P/>
</Description>
</ManSection>
<ManSection>
<Attr Arg="d" Name="UsedOperationsWithMultiplesAndCategoryGetters" Label="for IsDerivedMethod"/>
<Returns> The names of the operations used by the derivation <A>d</A>,
together with their multiplicities and category getters.
The result is a list consisting of lists of the form
<Code>[op_name, mult, getter]</Code>, where <Code>op_name</Code> is a string,
<Code>mult</Code> a positive integer and <Code>getter</Code> is a function or <Code>fail</Code>.
</Returns>
<Description>
<P/>
</Description>
</ManSection>
<ManSection>
<Oper Arg="d, weight, C" Name="InstallDerivationForCategory" Label="for IsDerivedMethod, IsPosInt, IsCapCategory"/>
<Description>
Install the derived method <A>d</A> for the category <A>C</A>.
The integer <A>weight</A> is the computed weight of the operation
implemented by this derivation.
</Description>
</ManSection>
<ManSection>
<Attr Arg="d" Name="FunctionCalledBeforeInstallation" Label="for IsDerivedMethod"/>
<Description>
Input is a derived method. Output is a unary function that takes as an input
a category and does not output anything. This function is always called before
the installation of the derived method for a concrete instance of a category.
</Description>
</ManSection>
<ManSection>
<Filt Arg="arg" Name="IsDerivedMethodGraph" Label="for IsAttributeStoringRep"/>
<Returns><K>true</K> or <K>false</K>
</Returns>
<Description>
A derivation graph consists of a set of operations and a set of derivations
specifying how some operations can be implemented in terms of other operations.
</Description>
</ManSection>
<ManSection>
<Oper Arg="operations" Name="MakeDerivationGraph" Label="for IsDenseList"/>
<Description>
Make a derivation graph containing the given set of operations and no derivations.
The argument <A>operations</A> should be a list of strings, the names of the
operations. The set of operations is fixed once the graph is created.
Derivations can be added to the graph by calling <C>AddDerivation</C>.
</Description>
</ManSection>
<ManSection>
<Oper Arg="graph, operations" Name="AddOperationsToDerivationGraph" Label="for IsDerivedMethodGraph, IsDenseList"/>
<Description>
Adds a list of operation names <A>operations</A> to a given derivation graph <A>graph</A>.
This is used in extensions of CAP which want to have their own basic operations,
but do not want to pollute the CAP kernel any more. Please use it with caution. If
a weight list/category was created before it will not be aware of the operations.
</Description>
</ManSection>
<ManSection>
<Func Arg="graph, target_op, description, used_ops_with_multiples_and_category_getters, func, weight, category_filter, loop_multiplier, category_getters, function_called_before_installation" Name="AddDerivation" />
<Description>
Add a derivation to a derivation graph.
</Description>
</ManSection>
<ManSection>
<Attr Arg="G" Name="Operations" Label="for IsDerivedMethodGraph"/>
<Description>
Gives the operations in the graph <A>G</A>, as a list of strings.
</Description>
</ManSection>
<ManSection>
<Oper Arg="G, op_name" Name="DerivationsUsingOperation" Label="for IsDerivedMethodGraph, IsString"/>
<Description>
Finds all the derivations in the graph <A>G</A> that use the operation named
<A>op_name</A>, and returns them as a list.
</Description>
</ManSection>
<ManSection>
<Oper Arg="G, op_name" Name="DerivationsOfOperation" Label="for IsDerivedMethodGraph, IsString"/>
<Description>
Finds all the derivations in the graph <A>G</A> targeting the operation named
<A>op_name</A> (that is, the derivations that provide implementations of this
operation), and returns them as a list.
</Description>
</ManSection>
</Section>
<Section Label="Chapter_Managing_Derived_Methods_Section_Managing_Derivations_in_a_Category">
<Heading>Managing Derivations in a Category</Heading>
<ManSection>
<Filt Arg="arg" Name="IsOperationWeightList" Label="for IsAttributeStoringRep"/>
<Returns><K>true</K> or <K>false</K>
</Returns>
<Description>
An operation weight list manages the use of derivations in a single category <Math>C</Math>.
For every operation, it keeps a weight value which indicates how costly it is
to perform that operation in the category <Math>C</Math>. Whenever a new operation is
implemented in <Math>C</Math>, the operation weight list should be notified about this and
given a weight to assign to this operation. It will then automatically install
all possible derived methods for <Math>C</Math> in such a way that every operation has the
smallest possible weight (the weight of a derived method is computed by using
the weights of the operations it uses).
</Description>
</ManSection>
<ManSection>
<Oper Arg="C, G" Name="MakeOperationWeightList" Label="for IsCapCategory, IsDerivedMethodGraph"/>
<Description>
Create the operation weight list for a category.
This should only be done once for every category, and the category should
afterwards remember the returned object.
The argument <A>C</A> is the CAP category this operation weight list is associated to,
and the argument <A>G</A> is a derivation graph containing operation names and derivations.
</Description>
</ManSection>
<ManSection>
<Attr Arg="owl" Name="DerivationGraph" Label="for IsOperationWeightList"/>
<Description>
Returns the derivation graph used by the operation weight list <A>owl</A>.
</Description>
</ManSection>
<ManSection>
<Attr Arg="owl" Name="CategoryOfOperationWeightList" Label="for IsOperationWeightList"/>
<Description>
Returns the CAP category associated to the operation weight list <A>owl</A>.
</Description>
</ManSection>
<ManSection>
<Oper Arg="owl, op_name" Name="CurrentOperationWeight" Label="for IsOperationWeightList, IsString"/>
<Description>
Returns the current weight of the operation named <A>op_name</A>.
</Description>
</ManSection>
<ManSection>
<Oper Arg="owl, d" Name="OperationWeightUsingDerivation" Label="for IsOperationWeightList, IsDerivedMethod"/>
<Description>
Finds out what the weight of the operation implemented by the derivation <A>d</A>
would be if we had used that derivation.
</Description>
</ManSection>
<ManSection>
<Oper Arg="owl, op_name" Name="DerivationOfOperation" Label="for IsOperationWeightList, IsString"/>
<Description>
Returns the derivation which is currently used to implement the operation
named <A>op_name</A>.
If the operation is not implemented by a derivation (that is, either implemented
directly or not implemented at all), then <C>fail</C> is returned.
</Description>
</ManSection>
<ManSection>
<Oper Arg="owl, op_name" Name="TriggerDerivationsUsingOperation" Label="for IsOperationWeightList, IsString"/>
<Description>
Performs a search from the operation <A>op_name</A>, and triggers all derivations
that give improvements over the current state.
This is used internally by <C>InstallDerivations</C> and <C>Reevaluate</C>.
It should normally not be necessary to call this function directly.
</Description>
</ManSection>
<ManSection>
<Oper Arg="owl" Name="Reevaluate" Label="for IsOperationWeightList"/>
<Description>
Reevaluate the installed derivations, installing better derivations if possible.
This should be called if new derivations become available for the category,
either because the category has acquired more knowledge about itself
(e.g. it is told that it is abelian)
or because new derivations have been added to the graph.
</Description>
</ManSection>
<ManSection>
<Oper Arg="owl" Name="Saturate" Label="for IsOperationWeightList"/>
<Description>
Saturates the derivation graph, i.e., calls reevaluate until
no more changes in the derivation graph occur.
</Description>
</ManSection>
<ManSection>
<Oper Arg="owl, op_name, weight" Name="AddPrimitiveOperation" Label="for IsOperationWeightList, IsString, IsInt"/>
<Description>
Add the operation named <A>op_name</A> to the operation weight list <A>owl</A>
with weight <A>weight</A>.
</Description>
</ManSection>
<ManSection>
<Oper Arg="owl, op_name" Name="PrintDerivationTree" Label="for IsOperationWeightList, IsString"/>
<Description>
Print a tree representation of the way the operation named <A>op_name</A>
is implemented in the category of the operation weight list <A>owl</A>.
</Description>
</ManSection>
<ManSection>
<Oper Arg="arg1,arg2,arg3" Name="PrintTree" Label="for IsObject, IsFunction, IsFunction"/>
<Description>
Prints a tree structure.
</Description>
</ManSection>
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