line_segmentize() returning incorrect result

[Robinlovelace]

line_segmentize() should always return n linestrings if it's going to work as expected in other functions. In this case n = 6 but the object returned has a length of 5:

sfc_integer = sf::st_linestring(
    cbind(
        c(418938.4, 418949.7, 418961),
        c(434303.2, 434280.1, 434257)
    )
) |>
  sf::st_sfc()
sfc_no_integer = sf::st_linestring(
    cbind(
        c(418938.4, 418949.7, 418961.1),
        c(434303.2, 434280.1, 434257)
    )
) |>
  sf::st_sfc()

rsgeo::line_segmentize(rsgeo::as_rsgeo(sfc_integer), n = 6) |>
  sf::st_as_sfc() |>
  sf::st_cast("LINESTRING") |>
  length()
#> [1] 5

rsgeo::line_segmentize(rsgeo::as_rsgeo(sfc_no_integer), n = 6) |>
  sf::st_as_sfc() |>
  sf::st_cast("LINESTRING") |>
  length()
#> [1] 6

^{Created on 2024-04-23 with reprex v2.1.0}

[Robinlovelace]

Essentially the same as #34, but this is projected data and with a decent distance between them. Could it be because one of the values in the coords is an integer I wonder...

[JosiahParry]

Repro:

    #[test]
    fn robin_test() {
        let linestring: LineString = vec![
            [418938.4, 434303.2],
            [418949.7, 434280.1],
            [418961.0, 434257.0],
        ]
        .into();
        let segments = linestring.line_segmentize(6).unwrap();
        assert_eq!(6, segments.0.len());
    }

[Robinlovelace]

Where does the underlying Rust code live? Must be some Rustaceans who will have good ideas on a fix.

[Robinlovelace]

Relevant code, from Josiah: https://github.com/georust/geo/blob/main/geo/src/algorithm/linestring_segment.rs