DATE     94/06/01

    Opérateur REAC                             See also :BLOQ ANTI 
    --------------                                       RELA RESO 
                                                         SYMT 
    | CHPO2 |  =  REAC  RIG1 | CHPO1 | ;
    | TAB2  |                | TAB1  |

    Description :
    ____________

    The REACTION operator constructs from the solution CHPO1 of
 a linear system on the first member of which conditions have
 been imposed, the variation of the second member allowing the
 verification of these conditions.

    Contents :
    __________

    RIG1  : object containing among other things imposed  
            conditions (RIGIDITE type)

    CHPO1 : solution field (obtained for instance by means of RESOU)
            (CHPOINT type)

    TAB1  : TABLE object defining the modes, pseudo-modes, ...
                - of BASE_MODALE subtype, or
                - ENSEMBLE_DE_BASES subtype

    CHPO2 : generated field of actions (CHPOINT type, 'discret' nature) 
            required for verifying the imposed conditions

    TAB2  : same structure as TAB1, but completed at the index
              'REACTION_MODALE' for the modes
              'REACTION' for the pseudo-modes,
            by the generated field of actions (CHPOINT type)

    Example :
    _________

    Given RIG1 a structure stiffness matrix, BLO1 the object
 containing the restraints and the relations, FORC1 a field of
 external forces, the displacement fields of the structure
 is obtained by :

             DEP1 = RESOU  ( RIG1 ET BLO1 ) FORC1 ;

    The reactions at the supports are obtained by :

             CHPO1 = REAC  BLO1 DEP1 ;

    Note :
    _______

    If RIG1 does not contain any elementary matrix associated
 with imposed conditions, an empty field CHPO2 should be
 created.