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D.15.2.22 qepcad

Procedure from library finitediff.lib (see finitediff_lib).

Usage:
qepcad(f); f a poly in the basering;

Return:
type list; gives back some constraints that are equivalent to f<1 (computed by QEPCAD);

Example:
 
LIB "finitediff.lib";
list D="Ux","Ut","U";
list P="a";
list V="t","x";
setinitials(V,D,P);
def s1=scheme(u(Ut)+a*u(Ux),laxfrX(Ux,U,x),laxfrT(Ut,U,x));
s1;
==> (-a*dt+dx)/(2*dx)*x^2+(a*dt+dx)/(2*dx)
def s2=errormap(s1);
s2;
==> (-a*dt+dx)/(dx)*i*cx*sx+(a*dt-dx)/(dx)*sx^2+1
def s3=ComplexValue(s2);s3;
==> (a^2*dt^2-dx^2)/(dx^2)*sx^2+1
qepcad(s3);
==> 0
==> 0
==> 0
==> 0
==> sx /= 0 /\ [ [ dx + a dt > 0 /\ dx - a dt > 0 ] \/ [ dx + a dt < 0 /\ dx \
   - a dt < 0 ] ]
==> 
==> [1]:
==>    sx
==> [2]:
==>    (a*dt+dx)
==> [3]:
==>    (-a*dt+dx)
==> [4]:
==>    (a*dt+dx)
==> [5]:
==>    (-a*dt+dx)


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