MathMap Attributes

MathMap Attributes

Seed

Random number seed

This attribute, which may take any integer value, determines the sequence of random numbers produced by the random number functions in MathMap expressions. It is set to an unpredictable default value when a MathMap is created, so that by default each MathMap uses a different set of random numbers.

If required, you may set this Seed attribute to a value of your choosing in order to produce repeatable behaviour from the random number functions. You may also enquire the Seed value (e.g. if an initially unpredictable value has been used) and then use it to reproduce the resulting sequence of random numbers, either from the same MathMap or from another one.

Clearing the Seed attribute gives it a new unpredictable default value.

SimpFI

Forward-inverse MathMap pairs simplify?

This attribute should be set to a true value if applying a MathMap's forward transformation, followed immediately by the matching inverse transformation will always restore the original set of coordinates. It indicates that AST may replace such a sequence of operations by an identity Mapping (a UnitMap) if it is encountered while simplifying a compound Mapping (e.g. using astSimplify).

By default, the MathMap_SimpFI "SimpFI" attribute is false, so that AST will not perform this simplification unless you have set MathMap_SimpFI "SimpFI" to indicate that it is safe to do so.

Notes

• For simplification to occur, the two MathMaps must be in series and be identical (with textually identical transformation functions). Functional equivalence is not sufficient.
• The consent of both MathMaps is required before simplification can take place. If either has a MathMap_SimpFI "SimpFI" value of false, then simplification will not occur.
• The MathMap_SimpFI "SimpFI" attribute controls simplification only in the case where a MathMap's forward transformation is followed by the matching inverse transformation. It does not apply if an inverse transformation is followed by a forward transformation. This latter case is controlled by the MathMap_SimpIF "SimpIF" attribute.
• The "forward" and "inverse" transformations referred to are those defined when the MathMap is created (corresponding to the "fwd" and "inv" parameters of its constructor function). If the MathMap is inverted, then the role of the MathMap_SimpFI "SimpFI" and MathMap_SimpIF "SimpIF" attributes will be interchanged.

SimpIF

This attribute should be set to a non-zero value if applying a MathMap's inverse transformation, followed immediately by the matching forward transformation will always restore the original set of coordinates. It indicates that AST may replace such a sequence of operations by an identity Mapping (a UnitMap) if it is encountered while simplifying a compound Mapping (e.g. using astSimplify).

By default, the MathMap_SimpIF "SimpIF" attribute is zero, so that AST will not perform this simplification unless you have set MathMap_SimpIF "SimpIF" to indicate that it is safe to do so.

Notes

see MathMap_SimpFI_Notes