refactored scan to also take pos arguments.

docs/scarpet/api/BlockIterations.md

@@ -2,11 +2,15 @@
 
 These functions help scan larger areas of blocks without using generic loop functions, like nested `loop`.
 
-### `scan(cx, cy, cz, dx, dy, dz, px?, py?, pz?, expr)`
+### `scan(cx, cy, cz, dx, dy, dz, px?, py?, pz?, expr)`, `scan(center, range, lower_range?, expr)`
 
-Evaluates expression over area of blocks defined by its center (`cx, cy, cz`), expanded in all directions 
-by `dx, dy, dz` blocks, or optionally in negative with `d` coords, and `p` coords in positive values. `expr` 
-receives `_x, _y, _z` as coords of current analyzed block and `_`, which represents the block itself.
+Evaluates expression over area of blocks defined by its center `center = (cx, cy, cz)`, expanded in all directions 
+by `range = (dx, dy, dz)` blocks, or optionally in negative with `range` coords, and `upper_range` coords in 
+positive values.
+`center` can be defined either as a three coordinates, list of three coords, or block value.
+`range` and `lower_range` can have the same representations, just if its a block, it computes the distance to the center
+as range instead of taking the values as is.
+`expr` receives `_x, _y, _z` as coords of current analyzed block and `_`, which represents the block itself.
 
 Returns number of successful evaluations of `expr` (with `true` boolean result) unless called in void context, 
 which would cause the expression not be evaluated for their boolean value.