Segments in Mojo

After implementing points in Mojo, with some assistance from ChatGPT and Phind, we now turn our attention to segments, which represent the next fundamental geometric structure preceding polylines (or simply lines).

A segment consists of a start point and an end point, rendering it an oriented entity. It is implemented as a Mojo structure, that implements a few methods, such as returning the segment start and end points, calculating the total or horizontal lenght, and so on.

To facilitate point copying when returning a segment's start or end point (via the start_point and end_point methods), the __copyinit__ method was introduced to the Point structure: 

  fn __copyinit__(inout self, existing: Point): self.coords = existing.coords 

 This method allows for efficient copying of point coordinates, which is crucial when working with segments. 

Moving on to the Segment structure, apart from incorporating several basic methods (such as dx, midx, length, horizontal_length, and others), two significant methods were added for calculating the azimuth and plunge of a Segment instance. These concepts are extensively utilized in geological contexts. 

The azimuth refers to the angle, within the horizontal plane, between the horizontal projection of the segment and the Y-axis. This angle is measured clockwise, commencing from the Y-axis, spanning from 0° to 360°. 

The plunge represents the dip of the segment in the vertical plane. It signifies the vertical angle between the horizontal plane and the segment. Its range extends from -90° to +90°, where positive values denote a downward dip, and negative values signify an upward dip. 

Both azimuth and plunge are expressed as Float64 values, but their values may remain undefined under specific circumstances. The azimuth becomes undefined when the segment is vertical or possesses zero length (i.e., when the start and end points coincide). Similarly, the plunge remains undefined when the segment's length is zero. 

To address these edge cases, both the azimuth() and plunge() methods return an Optional[Float64], with Optional being imported from the standard library's collections module. If the value is invalid, None is returned; otherwise, the valid value is returned. 

Notably, the valid return can also be encapsulated into an Optional — both approaches are considered valid. When presenting the result, the value must be extracted using the or_else method, where the input to this method serves as a placeholder for missing data. 

In the example code, a conventional no-data value frequently employed in Geographic Information Systems (GIS) was utilized by defining an alias: 

   alias NULL_ORIENTATION = -999999999.99999 

 This alias is subsequently applied as follows:

   print("Segment plunge:", segment.plunge().or_else(NULL_ORIENTATION)) 

In this scenario, when the result is valid, it will be printed; conversely, if the result is invalid, the no-data value defined in NULL_ORIENTATION will be displayed. 

By implementing these features, the Segment structure becomes more robust and versatile, capable of handling various geometric calculations essential in geological applications and beyond. 

 

The code is available at: https://gitlab.com/mauroalberti/kira