From 323ff7c5609eae3de6b2438ed3076ed18fddb0cd Mon Sep 17 00:00:00 2001
From: Matthias Goerner <1239022+unhyperbolic@users.noreply.github.com>
Date: Sun, 21 Jul 2024 16:38:06 -0700
Subject: [PATCH] Python code for short slopes: clean-ups.

---
 python/cusps/__init__.py      |  2 +-
 python/verify/short_slopes.py | 55 +++++++++++------------------------
 2 files changed, 18 insertions(+), 39 deletions(-)

diff --git a/python/cusps/__init__.py b/python/cusps/__init__.py
index 200465396..1ef898eb5 100644
--- a/python/cusps/__init__.py
+++ b/python/cusps/__init__.py
@@ -9,7 +9,7 @@
 
 def compute_cusp_shapes(manifold, verified, bits_prec=None):
     """
-    Compute verified cusp shapes (following the SnapPea kernel convention,
+    Compute cusp shapes. Following the SnapPea kernel convention,
     it returns the conjugate of the quotient of the translations
     corresponding to the longitude and meridian for each cusp.
 
diff --git a/python/verify/short_slopes.py b/python/verify/short_slopes.py
index a09b530a9..4ff6456d7 100644
--- a/python/verify/short_slopes.py
+++ b/python/verify/short_slopes.py
@@ -1,32 +1,14 @@
 from ..sage_helper import _within_sage
 from ..exceptions import InsufficientPrecisionError
+from ..math_basics import is_RealIntervalFieldElement, is_ComplexIntervalFieldElement
 
 import math
 
 if _within_sage:
     from sage.all import gcd
-
-    from sage.rings.real_mpfi import is_RealIntervalFieldElement
-    from sage.rings.complex_interval import is_ComplexIntervalFieldElement
-
-    # python's sqrt only work for floats
-    # They would fail or convert to float losing precision
-    from sage.all import sqrt
 else:
-    try:
-        # Python 3 has gcd in math
-        from math import gcd
-    except ImportError:
-        from fractions import gcd
-
-    # Otherwise, define our own sqrt which checks whether
-    # the given type defines a sqrt method and fallsback
-    # to python's log and sqrt which has the above drawback of
-    # potentially losing precision.
-    def sqrt(x):
-        if hasattr(x, 'sqrt'):
-            return x.sqrt()
-        return math.sqrt(x)
+    # Python 3 has gcd in math
+    from math import gcd
 
 # Reject computing short slopes if intervals for translations
 # are too wide (error is more than 1%).
@@ -66,35 +48,32 @@ def translations_from_cusp_shape_and_area(
 
     if kernel_convention:
         inv_cusp_shape = 1 / cusp_shape.conjugate()
-        scale = sqrt(cusp_area / _imag(inv_cusp_shape))
+        scale = (cusp_area / _imag(inv_cusp_shape)).sqrt()
         return (scale * inv_cusp_shape, scale)
     else:
-        scale = sqrt(cusp_area / _imag(cusp_shape))
+        scale = (cusp_area / _imag(cusp_shape)).sqrt()
         return (scale, cusp_shape * scale)
 
-
 def short_slopes_from_translations(translations, length=6):
 
     m_tran, l_tran = translations
 
-    if _within_sage:
-        if is_ComplexIntervalFieldElement(m_tran):
-            raise Exception("Meridian translation expected to be real")
-        if is_RealIntervalFieldElement(l_tran):
-            raise Exception("Longitude translation expected to be complex")
+    if is_ComplexIntervalFieldElement(m_tran):
+        raise Exception("Meridian translation expected to be real")
+    if is_RealIntervalFieldElement(l_tran):
+        raise Exception("Longitude translation expected to be complex")
 
-        is_interval_1 = is_RealIntervalFieldElement(m_tran)
-        is_interval_2 = is_ComplexIntervalFieldElement(l_tran)
+    is_interval_1 = is_RealIntervalFieldElement(m_tran)
+    is_interval_2 = is_ComplexIntervalFieldElement(l_tran)
 
-        if is_interval_1 != is_interval_2:
-            raise Exception("Mismatch of non-intervals and intervals.")
+    if is_interval_1 != is_interval_2:
+        raise Exception("Mismatch of non-intervals and intervals.")
 
-        if is_interval_1:
-            return _verified_short_slopes_from_translations(translations, length)
+    if is_interval_1:
+        return _verified_short_slopes_from_translations(translations, length)
 
     return _unverified_short_slopes_from_translations(translations, length)
 
-
 def _unverified_short_slopes_from_translations(translations, length=6):
     m_tran, l_tran = translations
 
@@ -118,7 +97,7 @@ def _unverified_short_slopes_from_translations(translations, length=6):
         max_real_range_sqr = length ** 2 - _imag(total_l_tran) ** 2
 
         if max_real_range_sqr >= 0:
-            max_real_range = sqrt(max_real_range_sqr)
+            max_real_range = max_real_range_sqr.sqrt()
 
             if l == 0:
                 min_m = 1
@@ -183,7 +162,7 @@ def _verified_short_slopes_from_translations(translations, length=6):
                 (- total_l_tran.real() + max_real_range) / m_tran)
 
             for m in range(min_m, max_m + 1):
-                if gcd(m, l) == 1:
+                if gcd(m, l) in [+1, -1]:
                     result.append((m, l))
 
     return result