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D.15.13.6 forward

Procedure from library finitediff.lib (see finitediff_lib).

Usage:
forward(U1,U2,var); U1, U2 are the names of occuring derivatives, var is a variable in the basering;

Return:
type vector; gives a predefined approximation of the forward approximation as often used in literature;

Note:
see also laxfrT,setinitials,scheme;

Example:
 
LIB "finitediff.lib";
list D="Ut","Ux","Uy","U";
list V="t","x","y";
list P="a","b";
setinitials(V,D,P);
forward(Ux,U,x);
==> [0,(dx),0,-x+1]
forward(Uy,U,y);
==> [0,0,(dy),-y+1]
forward(Ut,U,t);
==> [(dt),0,0,-t+1]