Modifiable Options within the gfun Package
Calling Sequence
Parameters
Description
Examples
Parameters(arg1, arg2, ... )
arg1, arg2, ...
-
argument(s) of the form name=val or name
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.
maxdegcoeff
maxordereqn
maxdegeqn
mindegcoeff
mindegeqn
minordereqn
optionsgf
If an argument is of the form name=val then this specifies the setting for the named variable.
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,
oldorder := Parameters(maxordereqn=7); # set new value and save old
...
Parameters(maxordereqn=oldorder); # restore previous value
If an argument is a name then the current value of the named variable is retrieved and returned as the function value.
When Parameters is called with many arguments, it returns an expression sequence containing the values.
The standard set of Parameters variables is:
NAME
VALUES
EXPLANATION
nonnegint
the maximal degree of the coefficients of equations returned by listtodiffeq, listtoalgeq, seriestodiffeq, and seriestoalgeq. The default value is 4.
the maximal degree for polynomial equations returned by listtoalgeq and seriestoalgeq. The default value is 3.
the maximal order for differential equations returned by listtodiffeq and seriestodiffeq. The default value is 3.
the minimal degree of the coefficients of equations returned by listtodiffeq, listtoalgeq, seriestodiffeq, and seriestoalgeq. The default value is 0.
the minimal degree for polynomial equations returned by listtoalgeq and seriestoalgeq. The default value is 2.
the minimal order for differential equations returned by listtodiffeq and seriestodiffeq. The default value is 1.
list
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.
The default is ['ogf', 'egf'] (ordinary and exponential generating functions).
For more information on the generating function types, see gfun/gftypes.
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.
Similarly, maxdegeqn and mindegeqn are used to bound the degree of algebraic equations.
Note, the old way of changing parameters by assigning the values to gfun:-<option> is deprecated.
gfun:-Parametersmaxordereqn=5,mindegcoeff
3,0
See Also
gfun
gfun/gftypes
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