Description
The index i is 0-based, and a negative number refers to location from the end of the polynomial.
i1 : R = ZZ[a..d];
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i2 : f = (a+2*b-3)^2
2 2
o2 = a + 4a*b + 4b - 6a - 12b + 9
o2 : R
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i3 : someTerms(f,0,1) -- the lead term
2
o3 = a
o3 : R
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i4 : someTerms(f,-1,1) -- the last term
o4 = 9
o4 : R
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i5 : someTerms(f,-2,2) -- the last 2 terms
o5 = - 12b + 9
o5 : R
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Here is an example where the coefficient ring is also a polynomial ring.
i6 : S = R[x,y,z];
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i7 : f = (x*(a-b)+y^2+a-1)^2
4 2 2 2 2 2 2
o7 = y + (2a - 2b)x*y + (a - 2a*b + b )x + (2a - 2)y + (2a - 2a*b - 2a
------------------------------------------------------------------------
2
+ 2b)x + a - 2a + 1
o7 : S
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i8 : someTerms(f,-1,1) -- the last term
2
o8 = a - 2a + 1
o8 : S
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i9 : someTerms(f,-2,2) -- the last 2 terms
2 2
o9 = (2a - 2a*b - 2a + 2b)x + a - 2a + 1
o9 : S
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