# Singular

#### D.6.1.11 charexp2poly

Procedure from library `alexpoly.lib` (see alexpoly_lib).

Assume:
v an intvec containing the characterictic exponents of an irreducible plane curve singularity. a a vector containing the coefficients of a parametrization given by x(t)=x^v[1], y(t)=a(1)t^v[2]+...+a[n-1]t^v[n], i.e. the entries of a are of type number.

Return:
A polynomial f in the first two variables of the basering, such that f defines an irreducible plane curve singularity with characteristic exponents v.

Note:
The entries in a should be of type number and the vector v should be the sequence of characteristic exponents of an irreducible plane curve singularity in order to get a sensible result,

Example:
 ```LIB "alexpoly.lib"; ring r=0,(x,y),dp; intvec v=8,12,14,17; vector a=[1,1,1]; poly f=charexp2poly(v,a); f; ==> -x17+8x16-20x15+17x14-16x13y+12x12y2-2x13+32x12y-16x11y2-8x10y3+x12-8x11y\ +20x10y2-16x9y3-4x9y2+16x8y3-2x7y4-8x6y5+6x6y4-8x5y5-4x3y6+y8 invariants(f)[1][1]; // The characteristic exponents of f. ==> 8,12,14,17 ```