Source code for sympy.geometry.entity

"""The definition of the base geometrical entity with attributes common to
all derived geometrical entities.




A GeometryEntity is any object that has special geometric properties.
A GeometrySet is a superclass of any GeometryEntity that can also
be viewed as a sympy.sets.Set.  In particular, points are the only
GeometryEntity not considered a Set.

Rn is a GeometrySet representing n-dimensional Euclidean space. R2 and
R3 are currently the only ambient spaces implemented.


from __future__ import division, print_function

from sympy.core.compatibility import is_sequence
from sympy.core.containers import Tuple
from sympy.core.basic import Basic
from sympy.core.symbol import _symbol
from sympy.core.sympify import sympify
from sympy.functions import cos, sin
from sympy.matrices import eye
from sympy.sets import Set
from sympy.utilities.misc import func_name
from sympy.multipledispatch import dispatch
from sympy.sets.handlers.union import union_sets
from sympy.sets.handlers.intersection import intersection_sets

# How entities are ordered; used by __cmp__ in GeometryEntity
ordering_of_classes = [

[docs]class GeometryEntity(Basic): """The base class for all geometrical entities. This class doesn't represent any particular geometric entity, it only provides the implementation of some methods common to all subclasses. """ def __cmp__(self, other): """Comparison of two GeometryEntities.""" n1 = self.__class__.__name__ n2 = other.__class__.__name__ c = (n1 > n2) - (n1 < n2) if not c: return 0 i1 = -1 for cls in self.__class__.__mro__: try: i1 = ordering_of_classes.index(cls.__name__) break except ValueError: i1 = -1 if i1 == -1: return c i2 = -1 for cls in other.__class__.__mro__: try: i2 = ordering_of_classes.index(cls.__name__) break except ValueError: i2 = -1 if i2 == -1: return c return (i1 > i2) - (i1 < i2) def __contains__(self, other): """Subclasses should implement this method for anything more complex than equality.""" if type(self) == type(other): return self == other raise NotImplementedError() def __getnewargs__(self): """Returns a tuple that will be passed to __new__ on unpickling.""" return tuple(self.args) def __ne__(self, o): """Test inequality of two geometrical entities.""" return not self == o def __new__(cls, *args, **kwargs): # Points are sequences, but they should not # be converted to Tuples, so use this detection function instead. def is_seq_and_not_point(a): # we cannot use isinstance(a, Point) since we cannot import Point if hasattr(a, 'is_Point') and a.is_Point: return False return is_sequence(a) args = [Tuple(*a) if is_seq_and_not_point(a) else sympify(a) for a in args] return Basic.__new__(cls, *args) def __radd__(self, a): """Implementation of reverse add method.""" return a.__add__(self) def __rdiv__(self, a): """Implementation of reverse division method.""" return a.__div__(self) def __repr__(self): """String representation of a GeometryEntity that can be evaluated by sympy.""" return type(self).__name__ + repr(self.args) def __rmul__(self, a): """Implementation of reverse multiplication method.""" return a.__mul__(self) def __rsub__(self, a): """Implementation of reverse substraction method.""" return a.__sub__(self) def __str__(self): """String representation of a GeometryEntity.""" from sympy.printing import sstr return type(self).__name__ + sstr(self.args) def _eval_subs(self, old, new): from sympy.geometry.point import Point, Point3D if is_sequence(old) or is_sequence(new): if isinstance(self, Point3D): old = Point3D(old) new = Point3D(new) else: old = Point(old) new = Point(new) return self._subs(old, new) def _repr_svg_(self): """SVG representation of a GeometryEntity suitable for IPython""" from sympy.core.evalf import N try: bounds = self.bounds except (NotImplementedError, TypeError): # if we have no SVG representation, return None so IPython # will fall back to the next representation return None svg_top = '''<svg xmlns="" xmlns:xlink="" width="{1}" height="{2}" viewBox="{0}" preserveAspectRatio="xMinYMin meet"> <defs> <marker id="markerCircle" markerWidth="8" markerHeight="8" refx="5" refy="5" markerUnits="strokeWidth"> <circle cx="5" cy="5" r="1.5" style="stroke: none; fill:#000000;"/> </marker> <marker id="markerArrow" markerWidth="13" markerHeight="13" refx="2" refy="4" orient="auto" markerUnits="strokeWidth"> <path d="M2,2 L2,6 L6,4" style="fill: #000000;" /> </marker> <marker id="markerReverseArrow" markerWidth="13" markerHeight="13" refx="6" refy="4" orient="auto" markerUnits="strokeWidth"> <path d="M6,2 L6,6 L2,4" style="fill: #000000;" /> </marker> </defs>''' # Establish SVG canvas that will fit all the data + small space xmin, ymin, xmax, ymax = map(N, bounds) if xmin == xmax and ymin == ymax: # This is a point; buffer using an arbitrary size xmin, ymin, xmax, ymax = xmin - .5, ymin -.5, xmax + .5, ymax + .5 else: # Expand bounds by a fraction of the data ranges expand = 0.1 # or 10%; this keeps arrowheads in view (R plots use 4%) widest_part = max([xmax - xmin, ymax - ymin]) expand_amount = widest_part * expand xmin -= expand_amount ymin -= expand_amount xmax += expand_amount ymax += expand_amount dx = xmax - xmin dy = ymax - ymin width = min([max([100., dx]), 300]) height = min([max([100., dy]), 300]) scale_factor = 1. if max(width, height) == 0 else max(dx, dy) / max(width, height) try: svg = self._svg(scale_factor) except (NotImplementedError, TypeError): # if we have no SVG representation, return None so IPython # will fall back to the next representation return None view_box = "{0} {1} {2} {3}".format(xmin, ymin, dx, dy) transform = "matrix(1,0,0,-1,0,{0})".format(ymax + ymin) svg_top = svg_top.format(view_box, width, height) return svg_top + ( '<g transform="{0}">{1}</g></svg>' ).format(transform, svg) def _svg(self, scale_factor=1., fill_color="#66cc99"): """Returns SVG path element for the GeometryEntity. Parameters ========== scale_factor : float Multiplication factor for the SVG stroke-width. Default is 1. fill_color : str, optional Hex string for fill color. Default is "#66cc99". """ raise NotImplementedError() def _sympy_(self): return self @property def ambient_dimension(self): """What is the dimension of the space that the object is contained in?""" raise NotImplementedError() @property def bounds(self): """Return a tuple (xmin, ymin, xmax, ymax) representing the bounding rectangle for the geometric figure. """ raise NotImplementedError()
[docs] def encloses(self, o): """ Return True if o is inside (not on or outside) the boundaries of self. The object will be decomposed into Points and individual Entities need only define an encloses_point method for their class. See Also ======== sympy.geometry.ellipse.Ellipse.encloses_point sympy.geometry.polygon.Polygon.encloses_point Examples ======== >>> from sympy import RegularPolygon, Point, Polygon >>> t = Polygon(*RegularPolygon(Point(0, 0), 1, 3).vertices) >>> t2 = Polygon(*RegularPolygon(Point(0, 0), 2, 3).vertices) >>> t2.encloses(t) True >>> t.encloses(t2) False """ from sympy.geometry.point import Point from sympy.geometry.line import Segment, Ray, Line from sympy.geometry.ellipse import Ellipse from sympy.geometry.polygon import Polygon, RegularPolygon if isinstance(o, Point): return self.encloses_point(o) elif isinstance(o, Segment): return all(self.encloses_point(x) for x in o.points) elif isinstance(o, Ray) or isinstance(o, Line): return False elif isinstance(o, Ellipse): return self.encloses_point( and \ self.encloses_point( Point( + o.hradius, and \ not self.intersection(o) elif isinstance(o, Polygon): if isinstance(o, RegularPolygon): if not self.encloses_point( return False return all(self.encloses_point(v) for v in o.vertices) raise NotImplementedError()
def equals(self, o): return self == o
[docs] def intersection(self, o): """ Returns a list of all of the intersections of self with o. Notes ===== An entity is not required to implement this method. If two different types of entities can intersect, the item with higher index in ordering_of_classes should implement intersections with anything having a lower index. See Also ======== sympy.geometry.util.intersection """ raise NotImplementedError()
[docs] def is_similar(self, other): """Is this geometrical entity similar to another geometrical entity? Two entities are similar if a uniform scaling (enlarging or shrinking) of one of the entities will allow one to obtain the other. Notes ===== This method is not intended to be used directly but rather through the `are_similar` function found in An entity is not required to implement this method. If two different types of entities can be similar, it is only required that one of them be able to determine this. See Also ======== scale """ raise NotImplementedError()
[docs] def reflect(self, line): """ Reflects an object across a line. Parameters ========== line: Line Examples ======== >>> from sympy import pi, sqrt, Line, RegularPolygon >>> l = Line((0, pi), slope=sqrt(2)) >>> pent = RegularPolygon((1, 2), 1, 5) >>> rpent = pent.reflect(l) >>> rpent RegularPolygon(Point2D(-2*sqrt(2)*pi/3 - 1/3 + 4*sqrt(2)/3, 2/3 + 2*sqrt(2)/3 + 2*pi/3), -1, 5, -atan(2*sqrt(2)) + 3*pi/5) >>> from sympy import pi, Line, Circle, Point >>> l = Line((0, pi), slope=1) >>> circ = Circle(Point(0, 0), 5) >>> rcirc = circ.reflect(l) >>> rcirc Circle(Point2D(-pi, pi), -5) """ from sympy import atan, Point, Dummy, oo g = self l = line o = Point(0, 0) if l.slope == 0: y = l.args[0].y if not y: # x-axis return g.scale(y=-1) reps = [(p, p.translate(y=2*(y - p.y))) for p in g.atoms(Point)] elif l.slope == oo: x = l.args[0].x if not x: # y-axis return g.scale(x=-1) reps = [(p, p.translate(x=2*(x - p.x))) for p in g.atoms(Point)] else: if not hasattr(g, 'reflect') and not all( isinstance(arg, Point) for arg in g.args): raise NotImplementedError( 'reflect undefined or non-Point args in %s' % g) a = atan(l.slope) c = l.coefficients d = -c[-1]/c[1] # y-intercept # apply the transform to a single point x, y = Dummy(), Dummy() xf = Point(x, y) xf = xf.translate(y=-d).rotate(-a, o).scale(y=-1 ).rotate(a, o).translate(y=d) # replace every point using that transform reps = [(p, xf.xreplace({x: p.x, y: p.y})) for p in g.atoms(Point)] return g.xreplace(dict(reps))
[docs] def rotate(self, angle, pt=None): """Rotate ``angle`` radians counterclockwise about Point ``pt``. The default pt is the origin, Point(0, 0) See Also ======== scale, translate Examples ======== >>> from sympy import Point, RegularPolygon, Polygon, pi >>> t = Polygon(*RegularPolygon(Point(0, 0), 1, 3).vertices) >>> t # vertex on x axis Triangle(Point2D(1, 0), Point2D(-1/2, sqrt(3)/2), Point2D(-1/2, -sqrt(3)/2)) >>> t.rotate(pi/2) # vertex on y axis now Triangle(Point2D(0, 1), Point2D(-sqrt(3)/2, -1/2), Point2D(sqrt(3)/2, -1/2)) """ newargs = [] for a in self.args: if isinstance(a, GeometryEntity): newargs.append(a.rotate(angle, pt)) else: newargs.append(a) return type(self)(*newargs)
[docs] def scale(self, x=1, y=1, pt=None): """Scale the object by multiplying the x,y-coordinates by x and y. If pt is given, the scaling is done relative to that point; the object is shifted by -pt, scaled, and shifted by pt. See Also ======== rotate, translate Examples ======== >>> from sympy import RegularPolygon, Point, Polygon >>> t = Polygon(*RegularPolygon(Point(0, 0), 1, 3).vertices) >>> t Triangle(Point2D(1, 0), Point2D(-1/2, sqrt(3)/2), Point2D(-1/2, -sqrt(3)/2)) >>> t.scale(2) Triangle(Point2D(2, 0), Point2D(-1, sqrt(3)/2), Point2D(-1, -sqrt(3)/2)) >>> t.scale(2, 2) Triangle(Point2D(2, 0), Point2D(-1, sqrt(3)), Point2D(-1, -sqrt(3))) """ from sympy.geometry.point import Point if pt: pt = Point(pt, dim=2) return self.translate(*(-pt).args).scale(x, y).translate(*pt.args) return type(self)(*[a.scale(x, y) for a in self.args]) # if this fails, override this class
[docs] def translate(self, x=0, y=0): """Shift the object by adding to the x,y-coordinates the values x and y. See Also ======== rotate, scale Examples ======== >>> from sympy import RegularPolygon, Point, Polygon >>> t = Polygon(*RegularPolygon(Point(0, 0), 1, 3).vertices) >>> t Triangle(Point2D(1, 0), Point2D(-1/2, sqrt(3)/2), Point2D(-1/2, -sqrt(3)/2)) >>> t.translate(2) Triangle(Point2D(3, 0), Point2D(3/2, sqrt(3)/2), Point2D(3/2, -sqrt(3)/2)) >>> t.translate(2, 2) Triangle(Point2D(3, 2), Point2D(3/2, sqrt(3)/2 + 2), Point2D(3/2, -sqrt(3)/2 + 2)) """ newargs = [] for a in self.args: if isinstance(a, GeometryEntity): newargs.append(a.translate(x, y)) else: newargs.append(a) return self.func(*newargs)
[docs] def parameter_value(self, other, t): """Return the parameter corresponding to the given point. Evaluating an arbitrary point of the entity at this parameter value will return the given point. Examples ======== >>> from sympy import Line, Point >>> from import t >>> a = Point(0, 0) >>> b = Point(2, 2) >>> Line(a, b).parameter_value((1, 1), t) {t: 1/2} >>> Line(a, b).arbitrary_point(t).subs(_) Point2D(1, 1) """ from sympy.geometry.point import Point from sympy.core.symbol import Dummy from sympy.solvers.solvers import solve if not isinstance(other, GeometryEntity): other = Point(other, dim=self.ambient_dimension) if not isinstance(other, Point): raise ValueError("other must be a point") T = Dummy('t', real=True) sol = solve(self.arbitrary_point(T) - other, T, dict=True) if not sol: raise ValueError("Given point is not on %s" % func_name(self)) return {t: sol[0][T]}
class GeometrySet(GeometryEntity, Set): """Parent class of all GeometryEntity that are also Sets (compatible with sympy.sets) """ def _contains(self, other): """sympy.sets uses the _contains method, so include it for compatibility.""" if isinstance(other, Set) and other.is_FiniteSet: return all(self.__contains__(i) for i in other) return self.__contains__(other) @dispatch(GeometrySet, Set) def union_sets(self, o): """ Returns the union of self and o for use with sympy.sets.Set, if possible. """ from sympy.sets import Union, FiniteSet # if its a FiniteSet, merge any points # we contain and return a union with the rest if o.is_FiniteSet: other_points = [p for p in o if not self._contains(p)] if len(other_points) == len(o): return None return Union(self, FiniteSet(*other_points)) if self._contains(o): return self return None @dispatch(GeometrySet, Set) def intersection_sets(self, o): """ Returns a sympy.sets.Set of intersection objects, if possible. """ from sympy.sets import Set, FiniteSet, Union from sympy.geometry import Point try: # if o is a FiniteSet, find the intersection directly # to avoid infinite recursion if o.is_FiniteSet: inter = FiniteSet(*(p for p in o if self.contains(p))) else: inter = self.intersection(o) except NotImplementedError: # sympy.sets.Set.reduce expects None if an object # doesn't know how to simplify return None # put the points in a FiniteSet points = FiniteSet(*[p for p in inter if isinstance(p, Point)]) non_points = [p for p in inter if not isinstance(p, Point)] return Union(*(non_points + [points])) def translate(x, y): """Return the matrix to translate a 2-D point by x and y.""" rv = eye(3) rv[2, 0] = x rv[2, 1] = y return rv def scale(x, y, pt=None): """Return the matrix to multiply a 2-D point's coordinates by x and y. If pt is given, the scaling is done relative to that point.""" rv = eye(3) rv[0, 0] = x rv[1, 1] = y if pt: from sympy.geometry.point import Point pt = Point(pt, dim=2) tr1 = translate(*(-pt).args) tr2 = translate(*pt.args) return tr1*rv*tr2 return rv def rotate(th): """Return the matrix to rotate a 2-D point about the origin by ``angle``. The angle is measured in radians. To Point a point about a point other then the origin, translate the Point, do the rotation, and translate it back: >>> from sympy.geometry.entity import rotate, translate >>> from sympy import Point, pi >>> rot_about_11 = translate(-1, -1)*rotate(pi/2)*translate(1, 1) >>> Point(1, 1).transform(rot_about_11) Point2D(1, 1) >>> Point(0, 0).transform(rot_about_11) Point2D(2, 0) """ s = sin(th) rv = eye(3)*cos(th) rv[0, 1] = s rv[1, 0] = -s rv[2, 2] = 1 return rv