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D.12.7.8 coords
Procedure from library rootsmr.lib (see rootsmr_lib).
- Usage:
- coords(f,b,i), f poly, b,i ideal
- Return:
- list of numbers: the coordinates of the class of f (mod i)
in the monomial basis b
- Assume:
- i is a Groebner basis and b is an ordered monomial basis of r/i,
r = basering
Example:
| | LIB "rootsmr.lib";
ring r = 0,(x,y),dp;
ideal i = x4-y2x,y2-13;
poly f = x3-xy+y-13+x4-y2x;
i = std(i);
ideal b = qbase(i);
b;
==> b[1]=x3y
==> b[2]=x3
==> b[3]=x2y
==> b[4]=x2
==> b[5]=xy
==> b[6]=x
==> b[7]=y
==> b[8]=1
coords(f,b,i);
==> [1]:
==> 0
==> [2]:
==> 1
==> [3]:
==> 0
==> [4]:
==> 0
==> [5]:
==> -1
==> [6]:
==> 0
==> [7]:
==> 1
==> [8]:
==> -13
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See also:
matbil;
matmult.
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