Modifiable Options within the gfun Package

Calling Sequence

Parameters(arg1, arg2, ... )

Parameters

arg1, arg2, ... - argument(s) of the form name=val or name

Description

• 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 described below.
• 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 Parameters variables and their default values are as follows:
• maxordereqn: the maximal order (or degree) for equations returned by listtodiffeq, seriestodiffeq, listtorec, seriestorec, listtoalgeq, and seriestoalgeq. The default value is infinity.
• minordereqn: the minimal order (or degree) for equations returned by listtodiffeq, seriestodiffeq, listtorec, seriestorec, listtoalgeq, and seriestoalgeq. The default value is 1.
• maxdegcoeffs: the maximal degree of polynomial coefficients allowed in guessed equations or recurrences. The default value is infinity.
• maxtotaldegree: an optional keyword bound on total degree, applicable only to algebraic and linear differential-equation guessing (listtoalgeq, seriestoalgeq, listtodiffeq, and seriestodiffeq). For algebraic equations it bounds the total degree in the independent variable and the unknown; for differential equations it bounds the total degree of the linear differential operator, counting x^j Dx^i with degree i+j. Its default value is infinity.
• checkterms: the number of nonzero input terms held out for validating a guessed relation. Zero coefficients between or after them are also held out as needed. The default value is 1.
• mode: either guessing or approximant. The default value is guessing.
• modulo: either 0, for rational arithmetic, or a prime. The default value is 0.
• optionsgf: 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 value is ['ogf'] (ordinary generating functions).

For more information on the generating function types, see gfun/gftypes.

Examples

> gfun:-Parameters(maxordereqn=5,minordereqn);

See Also

gfun, gfun/gftypes