spielwiese
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Last change
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checked in by Olaf Bachmann <obachman@…>, 26 years ago
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| 1 | LIB "hnoether.lib"; |
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| 2 | // ======== The irreducible case ======== |
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| 3 | ring s = 0,(x,y),ds; |
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| 4 | poly f = y4-2x3y2-4x5y+x6-x7; |
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| 5 | list hn = develop(f); |
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| 6 | show(hn[1]); // Hamburger-Noether matrix |
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| 7 | displayHNE(hn); // Hamburger-Noether developement |
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| 8 | setring s; |
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| 9 | displayInvariants(hn); |
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| 10 | // invariants(hn); will return the invariants as list |
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| 11 | param(hn); // partial parametrization of f |
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| 12 | // param takes the first variable as |
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| 13 | // except the ring has >2 variables |
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| 14 | ring extring=0,(x,y,t),ds; |
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| 15 | poly f=x3+2xy2+y2; |
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| 16 | list hn=develop(f,-1); |
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| 17 | param(hn); // partial parametrization of f |
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| 18 | list hn1=develop(f,6); |
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| 19 | param(hn1); // a better parametrization |
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| 20 | // instead or recomputing you may extend the developement: |
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| 21 | list hn2=extdevelop(hn,12); |
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| 22 | param(hn2); // a still better parametrization |
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| 23 | // ======== The reducible case ======== |
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| 24 | ring r = 0,(x,y),dp; |
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| 25 | poly f=x11-2y2x8-y3x7-y2x6+y4x5+2y4x3+y5x2-y6; |
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| 26 | // = (x5-1y2) * (x6-2x3y2-1x2y3+y4) |
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| 27 | list hn=reddevelop(f); |
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| 28 | show(hn[1][1]); // Hamburger-Noether matrix of 1st brach |
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| 29 | displayInvariants(hn); |
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| 30 | param(hn[2]); // parametrization of 2nd branch |
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| 31 | // extended parametrization of 1st |
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| 32 | $ |
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