Created Using Track Block Get Previous (markdown)

Using-Track-Block-Get-Previous.md

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+Pasted from gitter.
+
+Track blocks are what you place when you use the ride construction window i.e. they can be made up of multiple map elements. I know for your function its only one element but we should use track block get previous as it adds some protection. You have to pass the `x` and `y` coordinates of the start of the track block and the `map_element` of the tile. I suggest doing it like thus:
+
+```C
+rct_map_element* trackElement =
+map_get_track_element_at_of_type_seq(
+                    x,
+                    y,
+                    z / 8,
+                    trackType,
+                    0);
+
+rct_xy_element input;
+
+input.x = x;
+input.y = y;
+input.element = trackElement;
+track_begin_end output;
+```
+
+The `output` is a `track_begin_end` structure. The `track_begin_end` structure should in theory give `x`, `y` coordinates of the start and end of a track block and the `map_element`'s associated with either end. In general you should only concern yourself with the begin variables.
+
+Now using `track_block_get_previous` is pretty simple. It returns `false` if it fails to find the next track block and `true` if it does find another block. On failure do not trust the contents of the `output`.