Revert "Slopes between 2 indices and is_costas (#179)"

This reverts commit 58a070d.

Author: christianbean

CHANGELOG.md

@@ -13,8 +13,6 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
  - Matrix object
  - Function: Create Perm from a Matrix
  - Function: Create Matrix from Perm
- - Function: Get the slope between 2 indices
- - Function: Tells if perm is a Costas array
  - Enumeration strategy to check whether a class has finitely many simple permutations
 
 ### Changed

README.rst

@@ -159,10 +159,6 @@ There are numerous practical methods available:
     [(1, 2)]
     >>> p.major_index()
     2
-    >>> Perm((0, 1, 3, 2)).is_costas()
-    True
-    >>> Perm((2,1,0,4,3)).slope_between(0, 1)
-    -1.0
     >>> Perm((2,3,1,0)).matrix_repr()
     Matrix(4, {(0, 2): 1, (1, 3): 1, (2, 1): 1, (3, 0): 1})
     >>> Perm.from_matrix(Matrix(4, {(0, 2): 1, (1, 3): 1, (2, 1): 1, (3, 0): 1}))

permuta/patterns/perm.py

@@ -2929,49 +2929,6 @@ def cycle_notation(self) -> str:
 
     cycles = cycle_notation
 
-    def slope_between(self, first: int, second: int) -> float:
-        """Calculates the slope between the two given indices.
-
-        Examples:
-            >>> Perm((2,1,0,4,3)).slope_between(0, 1)
-            -1.0
-            >>> Perm((2,1,0,4,3)).slope_between(0, 2)
-            -1.0
-            >>> Perm((2,1,0,4,3)).slope_between(2, 3)
-            4.0
-        """
-        if not 0 <= first < second < len(self):
-            raise ValueError("Incorrect indices")
-        return (self[second] - self[first]) / (second - first)
-
-    def is_costas(self) -> bool:
-        """
-        Checks if permutation is a Costas Array, that is, all the slopes are different.
-
-        Examples:
-            >>> Perm((0, 1, 2, 3)).is_costas()
-            False
-            >>> Perm((0, 2, 1, 3)).is_costas()
-            False
-            >>> Perm((0, 3, 2, 1)).is_costas()
-            False
-            >>> Perm((0, 1, 3, 2)).is_costas()
-            True
-            >>> Perm((0, 2, 3, 1)).is_costas()
-            True
-            >>> Perm((0, 3, 1, 2)).is_costas()
-            True
-        """
-        width: int = len(self)
-        prev_slopes: Set[float] = set()
-        for first in range(width - 1):
-            for second in range(first + 1, width):
-                slope = self.slope_between(first, second)
-                if slope in prev_slopes:
-                    return False
-                prev_slopes.add(slope)
-        return True
-
     def to_svg(self, image_scale: float = 1.0) -> str:
         """Return the svg code to plot the permutation. The image size defaults to
         100x100 pixels and the parameter scales that.

tests/patterns/test_perm.py

@@ -3684,76 +3684,6 @@ def test_count_foreminima():
     assert Perm((3, 2, 1, 0)).count_foreminima() == 0
 
 
-def test_slope_between():
-    assert Perm((0, 1, 2)).slope_between(0, 2) == 1.0
-    assert Perm((0, 2, 1)).slope_between(1, 2) == -1.0
-    assert Perm((1, 0, 2)).slope_between(1, 2) == 2.0
-    assert Perm((1, 2, 0)).slope_between(0, 2) == -0.5
-    assert Perm((2, 0, 1)).slope_between(1, 2) == 1.0
-    assert Perm((2, 1, 0)).slope_between(1, 2) == -1.0
-    assert Perm((0, 1, 2, 3)).slope_between(0, 1) == 1.0
-    assert Perm((0, 1, 3, 2)).slope_between(1, 2) == 2.0
-    assert Perm((0, 2, 1, 3)).slope_between(1, 2) == -1.0
-    assert Perm((0, 2, 3, 1)).slope_between(2, 3) == -2.0
-    assert Perm((0, 3, 1, 2)).slope_between(2, 3) == 1.0
-    assert Perm((0, 3, 2, 1)).slope_between(2, 3) == -1.0
-    assert Perm((1, 0, 2, 3)).slope_between(2, 3) == 1.0
-    assert Perm((1, 0, 3, 2)).slope_between(0, 3) == 0.3333333333333333
-    assert Perm((1, 2, 0, 3)).slope_between(0, 3) == 0.6666666666666666
-    assert Perm((1, 2, 3, 0)).slope_between(0, 1) == 1.0
-    assert Perm((1, 3, 0, 2)).slope_between(2, 3) == 2.0
-    assert Perm((1, 3, 2, 0)).slope_between(1, 2) == -1.0
-    assert Perm((2, 0, 1, 3)).slope_between(1, 2) == 1.0
-    assert Perm((2, 0, 3, 1)).slope_between(1, 2) == 3.0
-    assert Perm((2, 1, 0, 3)).slope_between(0, 1) == -1.0
-    assert Perm((2, 1, 3, 0)).slope_between(2, 3) == -3.0
-    assert Perm((2, 3, 0, 1)).slope_between(1, 3) == -1.0
-    assert Perm((2, 3, 1, 0)).slope_between(0, 1) == 1.0
-    assert Perm((3, 0, 1, 2)).slope_between(1, 3) == 1.0
-    assert Perm((3, 0, 2, 1)).slope_between(1, 2) == 2.0
-    assert Perm((3, 1, 0, 2)).slope_between(0, 2) == -1.5
-    assert Perm((3, 1, 2, 0)).slope_between(2, 3) == -2.0
-    assert Perm((3, 2, 0, 1)).slope_between(1, 3) == -0.5
-    assert Perm((3, 2, 1, 0)).slope_between(2, 3) == -1.0
-
-
-def test_is_costas():
-    assert Perm(()).is_costas() == 1
-    assert Perm((0,)).is_costas() == 1
-    assert Perm((0, 1)).is_costas() == 1
-    assert Perm((1, 0)).is_costas() == 1
-    assert Perm((0, 1, 2)).is_costas() == 0
-    assert Perm((0, 2, 1)).is_costas() == 1
-    assert Perm((1, 0, 2)).is_costas() == 1
-    assert Perm((1, 2, 0)).is_costas() == 1
-    assert Perm((2, 0, 1)).is_costas() == 1
-    assert Perm((2, 1, 0)).is_costas() == 0
-    assert Perm((0, 1, 2, 3)).is_costas() == 0
-    assert Perm((0, 1, 3, 2)).is_costas() == 1
-    assert Perm((0, 2, 1, 3)).is_costas() == 0
-    assert Perm((0, 2, 3, 1)).is_costas() == 1
-    assert Perm((0, 3, 1, 2)).is_costas() == 1
-    assert Perm((0, 3, 2, 1)).is_costas() == 0
-    assert Perm((1, 0, 2, 3)).is_costas() == 1
-    assert Perm((1, 0, 3, 2)).is_costas() == 0
-    assert Perm((1, 2, 0, 3)).is_costas() == 1
-    assert Perm((1, 2, 3, 0)).is_costas() == 0
-    assert Perm((1, 3, 0, 2)).is_costas() == 0
-    assert Perm((1, 3, 2, 0)).is_costas() == 1
-    assert Perm((2, 0, 1, 3)).is_costas() == 1
-    assert Perm((2, 0, 3, 1)).is_costas() == 0
-    assert Perm((2, 1, 0, 3)).is_costas() == 0
-    assert Perm((2, 1, 3, 0)).is_costas() == 1
-    assert Perm((2, 3, 0, 1)).is_costas() == 0
-    assert Perm((2, 3, 1, 0)).is_costas() == 1
-    assert Perm((3, 0, 1, 2)).is_costas() == 0
-    assert Perm((3, 0, 2, 1)).is_costas() == 1
-    assert Perm((3, 1, 0, 2)).is_costas() == 1
-    assert Perm((3, 1, 2, 0)).is_costas() == 0
-    assert Perm((3, 2, 0, 1)).is_costas() == 1
-    assert Perm((3, 2, 1, 0)).is_costas() == 0
-
-
 def test_matrix_class():
     assert Matrix(0) == Matrix(0)
     matrix = Matrix(size=3, elements={(0, 0): 1, (1, 1): 1, (2, 2): 1})