# Singular          #### D.15.12.36 derivationToString

Procedure from library `difform.lib` (see difform_lib).

Usage:
derivationToString(phi,#); phi derivation, # list

Return:
the derivation as a string, describing the image of the degree-1 generators, optionally ordered by a given monomial ordering on the generators

Remarks:
To sort the images of the generators in the output string, difformListSort is used.

Note:
to define an ordering for the generators, one can use:
- # = 'gen'
- #: a monomial ordering as string
- #: an optional weight vector
the standard ordering is the ordering of the differential algebra

Example:
 ```LIB "difform.lib"; ring R = 0,(x,y,z),dp; diffAlgebra(); ==> // The differential algebra Omega_R was constructed and the differential \ forms dx, dy, dz are available. list L; L = list(dx,dy,dz); L = list(x2,y-23xz,xz4); derivation phi = L; /////////////////////////////////// // String with standard ordering // /////////////////////////////////// print(derivationToString(phi)); ==> Omega_R^1 --> R ==> dz |--> xz4 ==> dy |--> -23xz+y ==> dx |--> x2 ==> ////////////////////////////////// // String with changed ordering // ////////////////////////////////// print(derivationToString(phi,"gen","wp",intvec(-1,-1,1))); ==> Omega_R^1 --> R ==> dy |--> -23xz+y ==> dx |--> x2 ==> dz |--> xz4 ==> kill Omega_R,dx,dy,dz,L,phi; ``` 