Function: solvestep
Section: sums
C-Name: solvestep0
Prototype: V=GGGED0,L,p
Help: solvestep(X=a,b,step,expr,{fl=0}): find zeros of a function in the real
 interval [a,b] by naive interval splitting.
Wrapper: (,,,G)
Description:
  (gen,gen,gen,gen, ?0$):gen:prec solvestep(${4 cookie}, ${4 wrapper}, $1, $2, $3, $5, prec)
Doc: find zeros of a continuous function in the real interval $[a,b]$ by naive
 interval splitting. This function is heuristic and may or may not find the
 intended zeros. Binary digits of \fl mean

 \item 1: return as soon as one zero is found, otherwise return all
 zeros found;

 \item 2: refine the splitting until at least one zero is found
 (may loop indefinitely if there are no zeros);

 \item 4: do a multiplicative search (we must have $a > 0$), otherwise
 an additive search; \var{step} is the multiplicative or additive step.

 \item 8: refine the splitting until at least one zero is very close to an
 integer.

 \synt{solvestep}{void *E,GEN (*eval)(void*,GEN),GEN a,GEN b,GEN step,long flag,long prec}.
