[PostGIS] #5082: st_linelocatepoint returns value over 1

[PostGIS]

#5082: st_linelocatepoint returns value over 1
----------------------+--------------------------------
  Reporter:  andrest  |      Owner:  pramsey
      Type:  defect   |     Status:  new
  Priority:  medium   |  Milestone:  PostGIS PostgreSQL
 Component:  postgis  |    Version:  3.1.x
Resolution:           |   Keywords:  st_linelocatepoint
----------------------+--------------------------------
Comment (by ostro):

 I managed to reproduce this error. I use `postgis=3.4`.

 === Reproduction data
 This is the SQL code, where the invalid value (`1.0000000000000002`) is
 returned:
 {{{#!sql
 select ST_LineLocatePoint(
         'LINESTRING (614506.766313283 390577.5124384557, 614494.089082674
 390574.5586551775, 614494.8569439995 390562.1301508558, 614493.5246928157
 390549.7664042029, 614486.5713433414 390544.32637928444, 614487.6296766759
 390492.9548792321, 614487.6296766759 390492.9548792321)'::geometry,
         'POINT (614487.6296766759 390492.9548792321)'::geometry
 ) > 1
 }}}

 Note that depending on your program, you may see just `1`. In that case,
 cast `ST_LineLocatePoint` result to text, to see value with full
 precision.

 === Possible solution

 This seems to be a normal floating point error that happens in almost all
 programming languages (using IEEE 754). Consider this rust code:
 {{{#!text/html
 fn main() {
     let a: f64 = 100.0;
     let b: f64 = 0.000_01 * 10_000_000.0;
     let c: f64 = b / a;
     println!("{:.20}", c);
 }
 }}}

 If I decoded correctly, this is the
 [https://gitea.osgeo.org/postgis/postgis/src/commit/799c1d873c39a3ae9c475c24e9dfeda6078aa956/postgis/geography_measurement.c#L1395
 function code] that calls this
 [https://gitea.osgeo.org/postgis/postgis/src/commit/799c1d873c39a3ae9c475c24e9dfeda6078aa956/liblwgeom/lwgeodetic_measures.c#L551
 function library]. So maybe simple `if` will solve this problem?
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5082#comment:2>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.