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 TODO:
 * maybe make the explosion table function return a perlin explosion table
-* add documentation here instead of
-	https://dev.minetest.net/User:Hybrid_Dog#vector_extras
-* implement 3D scanline search
-* add vector.hollowsphere, less positions than WorldEdit hollowsphere
+* Figure out and implement 3D scanline search
+* Add vector.hollowsphere, less positions than WorldEdit hollowsphere
+* Add unit tests
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+
+# Vector helpers added by this mod
+
+## Helpers which return many positions for a shape, e.g. a line
+
+### Line functions
+
+These may be deprecated since raycasting has been added to minetest.
+See e.g. `minetest.line_of_sight`.
+
+* `vector.line([pos, dir[, range][, alt]])`: returns a table of vectors
+    * `dir` is either a direction (when range is a number) or
+      the start position (when range is the end position).
+    * If alt is true, an old path calculation is used.
+* `vector.twoline(x, y)`: can return e.g. `{{0,0}, {0,1}}`
+    * This is a lower-level function than `vector.line`; it can be used for
+      a 2D line.
+* `vector.threeline(x, y, z)`: can return e.g. `{{0,0,0}, {0,1,0}}`
+    * Similar to `vector.twoline`; this one is for the 3D case.
+    * The parameters should be integers.
+* `vector.rayIter(pos, dir)`: returns an iterator for a for loop
+    * `pos` can have non-integer values
+* `vector.fine_line([pos, dir[, range], scale])`: returns a table of vectors
+    * Like `vector.line` but allows non-integer positions
+    * It uses `vector.rayIter`.
+
+
+### Flood Fill
+
+* `vector.search_2d(go_test, x0, y0, allow_revisit, give_map)`: returns e.g.
+  `{{0,0}, {0,1}}`
+    * This function uses a Flood Fill algorithm, so it can be used to detect
+      positions connected to each other in 2D.
+    * `go_test(x, y)` should be a function which returns true iff the algorithm
+      can "fill" at the position `(x, y)`.
+    * `(x0, y0)` defines the start position.
+    * If `allow_revisit` is false (the default), the function
+      invokes `go_test` only once at every potential position.
+    * If `give_map` is true (default is false), the function returns the
+      marked table, whose indices are 2D vector indices, instead of a list of
+      2D positions.
+* `vector.search_3d(can_go, startpos, apply_move, moves)`: returns FIXME
+    * FIXME
+
+
+### Other Shapes
+
+* `vector.explosion_table(r)`: returns e.g. `{{pos1}, {pos2, true}}`
+    * The returned list of positions and boolean represents a sphere;
+      if the boolean is true, the position is on the outer side of the sphere.
+    * It might be used for explosion calculations; but `vector.explosion_perlin`
+      should make more realistic holes.
+* `vector.explosion_perlin(rmin, rmax[, nparams])`: returns e.g.
+  `{{pos1}, {pos2, true}}`
+    * This function is similar to `vector.explosion_table`; the positions
+      do not represent a sphere but a more complex hole which is calculated
+      with the help of perlin noise.
+    * `rmin` and `rmax` represent the minimum and maximum radius,
+      and `nparams` (which has a default value) are parameters for the perlin
+      noise.
+* `vector.circle(r)`: returns a table of vectors
+    * The returned positions represent a circle of radius `r` along the x and z
+      directions; the y coordinates are all zero.
+* `vector.ring(r)`: returns a table of vectors
+    * This function is similar to `vector.circle`; the positions are all
+      touching each other (i.e. they are connected on whole surfaces and not
+      only infinitely thin edges), so it is called `ring` instead of `circle`
+    * `r` can be a non-integer number.
+* `vector.throw_parabola(pos, vel, gravity, point_count, time)`
+    * FIXME: should return positions along a parabola so that moving objects
+      collisions can be calculated
+* `vector.triangle(pos1, pos2, pos3)`: returns a table of positions, a number
+  and a table with barycentric coordinates
+    * This function calculates integer positions for a triangle defined by
+      `pos1`, `pos2` and `pos3`, so it can be used to place polygons in
+      minetest.
+    * The returned number is the number of positions.
+    * The barycentric coordinates are specified in a table with three elements;
+      the first one corresponds to `pos1`, etc.
+
+
+## Helpers for various vector calculations
+
+* `vector.sort_positions(ps[, preferred_coords])`
+    * Sorts a table of vectors `ps` along the coordinates specified in the
+      table `preferred_coords` in-place.
+    * If `preferred_coords` is omitted, it sorts along z, y and x in this order,
+      where z has the highest priority.
+* `vector.maxnorm(v)`: returns the Tschebyshew norm of `v`
+* `vector.sumnorm(v)`: returns the Manhattan norm of `v`
+* `vector.pnorm(v, p)`: returns the `p` norm of `v`
+* `vector.inside(pos, minp, maxp)`: returns a boolean
+    * Returns true iff `pos` is within the closed AABB defined by `minp`
+      and `maxp`.
+* `vector.minmax(pos1, pos2)`: returns two vectors
+    * This does the same as `worldedit.sort_pos`.
+    * The components of the second returned vector are all bigger or equal to
+      those of the first one.
+* `vector.move(pos1, pos2, length)`: returns a vector
+    * Go from `pos1` `length` metres to `pos2` and then round to the nearest
+      integer position.
+    * Made for rubenwardy
+* `vector.from_number(i)`: returns `{x=i, y=i, z=i}`
+* `vector.chunkcorner(pos)`: returns a vector
+    * Returns the mapblock position of the mapblock which contains
+      the integer position `pos`
+* `vector.point_distance_minmax(p1, p2)`: returns two numbers
+    * Returns the minimum and maximum of the absolute component-wise distances
+* `vector.collision(p1, p2)` FIXME
+* `vector.update_minp_maxp(minp, maxp, pos)`
+    * Can change `minp` and `maxp` so that `pos` is within the AABB defined by
+      `minp` and `maxp`
+* `vector.unpack(v)`: returns three numbers
+    * Returns `v.z, v.y, v.x`
+* `vector.get_max_coord(v)`: returns a string
+    * Returns `"x"`, `"y"` or `"z"`, depending on which component has the
+      biggest value
+* `vector.get_max_coords(v)`: returns three strings
+    * Similar to `vector.get_max_coord`; it returns the coordinates in the order
+      of their component values
+    * Example: `vector.get_max_coords{x=1, y=5, z=3}` returns `"y", "z", "x"`
+* `vector.serialize(v)`: returns a string
+    * In comparison to `minetest.serialize`, this function uses a more compact
+      string for the serialization.
+
+
+## Minetest-specific helper functions
+
+* `vector.straightdelay([length, vel[, acc]])`: returns a number
+    * Returns the time an object takes to move `length` if it has velocity `vel`
+      and acceleration `acc`
+* `vector.sun_dir([time])`: returns a vector or nil
+    * Returns the vector which points to the sun
+    * If `time` is omitted, it uses the current time.
+    * This function does not yet support the moon;
+      at night it simply returns `nil`.
+
+
+## Helpers which I don't recommend to use now
+
+* `vector.pos_to_string(pos)`: returns a string
+    * It is similar to `minetest.pos_to_string`; it uses a different format:
+      `"("..pos.x.."|"..pos.y.."|"..pos.z..")"`
+* `vector.zero`
+    * The zero vector `{x=0, y=0, z=0}`
+* `vector.quickadd(pos, [z],[y],[x])`
+    * Adds values to the vector components in-place
+
+
+## Deprecated helpers
+
+* `vector.plane`
+    * should be removed soon; it should have done the same as vector.triangle
+