| #### D.15.2.43 derivationContractionGen Procedure from library `difform.lib` (see difform_lib). Usage: derivationContractionGen(phi,d_gen); phi derivation, d_gen difform Assume: d_gen is a generator of the differential algebra Return: the image of d_gen under the contraction map i_phi Remarks: The formula for the contraction map applied to a generator of degree l is given by: i_phi^(l)(dx_k*...*dx_j) = sum(i=1,..l)(-1)^(i+1) * phi(dx_i) * (dx_k*...*dx_j / dx_i) Note: this procedure should only be applied to generators See also: derivationContraction.

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