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Calling Sequence
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Parameters(arg1, arg2, ... )
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Parameters
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arg1, arg2, ...
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-
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argument(s) of the form name=val or name
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Description
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The Parameters command is used to set and query variables that affect the computation inside gfun. The variables that can be set and queried are as follows.
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maxdegcoeff
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maxordereqn
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maxdegeqn
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mindegcoeff
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mindegeqn
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minordereqn
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optionsgf
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If an argument is of the form name=val then this specifies the setting for the named variable.
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For each argument of this type, Parameters returns the old value of the argument. This is convenient when you want to change and later restore a value, for example,
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oldorder := Parameters(maxordereqn=7); # set new value and save old
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...
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Parameters(maxordereqn=oldorder); # restore previous value
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If an argument is a name then the current value of the named variable is retrieved and returned as the function value.
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When Parameters is called with many arguments, it returns an expression sequence containing the values.
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The standard set of Parameters variables is:
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NAME
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VALUES
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EXPLANATION
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maxdegcoeff
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nonnegint
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the maximal degree of the coefficients of equations returned by listtodiffeq, listtoalgeq, seriestodiffeq, and seriestoalgeq. The default value is .
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maxdegeqn
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nonnegint
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the maximal degree for polynomial equations returned by listtoalgeq and seriestoalgeq. The default value is .
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maxordereqn
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nonnegint
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the maximal order for differential equations returned by listtodiffeq and seriestodiffeq. The default value is .
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mindegcoeff
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nonnegint
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the minimal degree of the coefficients of equations returned by listtodiffeq, listtoalgeq, seriestodiffeq, and seriestoalgeq. The default value is .
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mindegeqn
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nonnegint
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the minimal degree for polynomial equations returned by listtoalgeq and seriestoalgeq. The default value is .
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minordereqn
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nonnegint
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the minimal order for differential equations returned by listtodiffeq and seriestodiffeq. The default value is .
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optionsgf
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list
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specifies the list of types of generating functions considered by listtoalgeq, listtodiffeq, listtohypergeom, listtolist, listtoratpoly, listtorec, listtoseries, seriestoalgeq, seriestodiffeq, seriestohypergeom, seriestolist, seriestoratpoly, seriestorec, and seriestoseries.
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The default is ['ogf', 'egf'] (ordinary and exponential generating functions).
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For more information on the generating function types, see gfun/gftypes.
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For example, if the listtodiffeq function is used, only those linear differential equations whose order is between minordereqn and maxordereqn and whose coefficients have a degree between mindegcoeff and maxdegcoeff are considered.
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Similarly, maxdegeqn and mindegeqn are used to bound the degree of algebraic equations.
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Note, the old way of changing parameters by assigning the values to gfun:-<option> is deprecated.
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Examples
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>
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