### AST_MAPSPLIT

Split a Mapping up into parallel component Mappings

#### Description:

This routine creates a new Mapping which connects specified inputs within a supplied Mapping to the corresponding outputs of the supplied Mapping. This is only possible if the specified inputs correspond to some subset of the Mapping outputs. That is, there must exist a subset of the Mapping outputs for which each output depends only on the selected Mapping inputs, and not on any of the inputs which have not been selected. Also, any output which is not in this subset must not depend on any of the selected inputs. If these conditions are not met by the supplied Mapping, then an AST__NULL Mapping pointer is returned.

#### Invocation

CALL AST_MAPSPLIT( THIS, NIN, IN, OUT, MAP, STATUS )

#### Arguments

##### THIS = INTEGER (Given)
Pointer to the Mapping to be split.
##### NIN = INTEGER (Given)
The number of inputs to pick from THIS.
##### IN( NIN ) = INTEGER (Given)
An array holding the indices within the supplied Mapping of the inputs which are to be picked from the Mapping. If " Nin" is the number of inputs of the supplied Mapping, then each element should have a value in the range 1 to Nin.
##### OUT( $\ast$ ) = INTEGER (Returned)
An array in which to return the indices of the outputs of the supplied Mapping which are fed by the picked inputs. A value of one is used to refer to the first Mapping output. The supplied array should have a length at least equal to the number of outputs in the supplied Mapping. The number of values stored in the array on exit will equal the number of outputs in the returned Mapping. The i’ th element in the returned array holds the index within the supplied Mapping which corresponds to the i’ th output of the returned Mapping.
##### MAP = INTEGER (Returned)
The returned Mapping. This Mapping will have NIN inputs (the number of outputs may be different to NIN). AST__NULL is returned if the supplied Mapping has no subset of outputs which depend only on the selected inputs. The returned Mapping is a deep copy of the required parts of the supplied Mapping.

#### Notes:

• If this routine is invoked with the global error status set, or if it should fail for any reason, then AST__NULL will be returned for MAP.