Refactored edge cases handling

2 files changed, 19 insertions, 12 deletions

diff --git a/szilagyi/nomogram.py b/szilagyi/nomogram.py
index 8c567d7..4dcd141 100644
--- a/szilagyi/nomogram.py
+++ b/szilagyi/nomogram.py
@@ -4,6 +4,11 @@ from collections import deque
 from . import _dataset
 
 
+class NomogramEdgeCase(Exception):
+	def __init__(self, value):
+		self.value = value
+
+
 def look_downwards(data, x, start):
 	for i in range(start, 0, -1):
 		if data[i - 1].x < x:
@@ -46,24 +51,29 @@ def find_boundary_curves(swis, x, y):
 		middle = segments[1][1]
 		run = middle[j].x - middle[i].x
 		if run == 0:
-			raise RuntimeError  # tidy up dataset
+			raise NomogramEdgeCase(segments[1][0])  # Tidy up the dataset nonetheless
 		slope = (middle[j].y - middle[i].y) / run
 		intercept = middle[j].y - slope * middle[j].x
 		value = slope * x + intercept
 		if value == y:
-			raise RuntimeError  # Exactly on point; SWI == index
+			raise NomogramEdgeCase(segments[1][0])
 		if value < y:
 			segments.popleft()
 		else:
 			segments.pop()
 	if len(segments) == 1:
-		raise RuntimeError  # SWI == -10
+		raise NomogramEdgeCase(-10)
 	return segments
 
 
 def calculate_swi(x, y):
-	low, high = find_boundary_curves(_dataset.INDICES, x, y)
-	vec = _dataset.Vector(x, y)
-	dist_to_low = min(abs(vec - p) for p in (low[1][low[2]], low[1][low[2]]))
-	dist_to_high = min(abs(vec - p) for p in (high[1][high[2]], high[1][high[2]]))
-	return dist_to_low / (dist_to_low + dist_to_high) * (high[0] - low[0]) + low[0]
+	try:
+		low, high = find_boundary_curves(_dataset.INDICES, x, y)
+		vec = _dataset.Vector(x, y)
+		dist_to_low = min(abs(vec - p) for p in (low[1][low[2]], low[1][low[2]]))
+		dist_to_high = min(abs(vec - p) for p in (high[1][high[2]], high[1][high[2]]))
+		return dist_to_low / (dist_to_low + dist_to_high) * (high[0] - low[0]) + low[0]
+	except NomogramEdgeCase as edge:
+		return edge.value
+	except IndexError:
+		return -10  # Reduce the amount of cases in which it may occur
diff --git a/szilagyi/plots.py b/szilagyi/plots.py
index 44782d6..9453919 100644
--- a/szilagyi/plots.py
+++ b/szilagyi/plots.py
@@ -23,10 +23,7 @@ if __name__ == "__main__":
 		row = []
 		for x_scaled in range(0, 1000):
 			x = x_scaled / 25
-			try:
-				swi = calculate_swi(x, y)
-			except (IndexError, RuntimeError):
-				swi = -10
+			swi = calculate_swi(x, y)
 			row.append(swi)
 		C.append(row)
 	plot.pcolormesh(X, Y, C, cmap='viridis', vmin=-10, vmax=10, rasterized=True)