### Locators

It may be useful to have a specific locator code for locating certain singularities (cf. section 2.4.4). To use a specific locator you must set the option Locators. This is a vector in which the index of an element corresponds to the index of a singularity. Setting the entry to means the presence of a user-defined locator. The continuer has stored the handles to the locators in the variable `cds.curve_locator` and will then make a call to
`[x,v]=feval(cds.curve_locate,i,x1,v1,x2,v2)`
to locate singularity which was detected between `x1` and `x2` with their corresponding tangent vectors `v1` and `v2`. It must return the located point and the tangent vector at that point. If the locator was unable to find a point it should return `x = []`.