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87 lines
2.6 KiB
87 lines
2.6 KiB
from pytest import raises
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from sympy import symbols
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from sympy.physics.mechanics import (RigidBody, Particle, ReferenceFrame, Point,
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outer, dynamicsymbols, Force, Torque)
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from sympy.physics.mechanics.loads import gravity, _parse_load
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def test_force_default():
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N = ReferenceFrame('N')
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Po = Point('Po')
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f1 = Force(Po, N.x)
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assert f1.point == Po
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assert f1.force == N.x
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assert f1.__repr__() == 'Force(point=Po, force=N.x)'
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# Test tuple behaviour
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assert isinstance(f1, tuple)
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assert f1[0] == Po
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assert f1[1] == N.x
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assert f1 == (Po, N.x)
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assert f1 != (N.x, Po)
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assert f1 != (Po, N.x + N.y)
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assert f1 != (Point('Co'), N.x)
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# Test body as input
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P = Particle('P', Po)
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f2 = Force(P, N.x)
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assert f1 == f2
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def test_torque_default():
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N = ReferenceFrame('N')
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f1 = Torque(N, N.x)
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assert f1.frame == N
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assert f1.torque == N.x
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assert f1.__repr__() == 'Torque(frame=N, torque=N.x)'
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# Test tuple behaviour
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assert isinstance(f1, tuple)
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assert f1[0] == N
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assert f1[1] == N.x
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assert f1 == (N, N.x)
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assert f1 != (N.x, N)
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assert f1 != (N, N.x + N.y)
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assert f1 != (ReferenceFrame('A'), N.x)
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# Test body as input
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rb = RigidBody('P', frame=N)
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f2 = Torque(rb, N.x)
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assert f1 == f2
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def test_gravity():
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N = ReferenceFrame('N')
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m, M, g = symbols('m M g')
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F1, F2 = dynamicsymbols('F1 F2')
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po = Point('po')
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pa = Particle('pa', po, m)
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A = ReferenceFrame('A')
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P = Point('P')
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I = outer(A.x, A.x)
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B = RigidBody('B', P, A, M, (I, P))
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forceList = [(po, F1), (P, F2)]
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forceList.extend(gravity(g * N.y, pa, B))
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l = [(po, F1), (P, F2), (po, g * m * N.y), (P, g * M * N.y)]
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for i in range(len(l)):
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for j in range(len(l[i])):
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assert forceList[i][j] == l[i][j]
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def test_parse_loads():
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N = ReferenceFrame('N')
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po = Point('po')
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assert _parse_load(Force(po, N.z)) == (po, N.z)
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assert _parse_load(Torque(N, N.x)) == (N, N.x)
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f1 = _parse_load((po, N.x)) # Test whether a force is recognized
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assert isinstance(f1, Force)
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assert f1 == Force(po, N.x)
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t1 = _parse_load((N, N.y)) # Test whether a torque is recognized
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assert isinstance(t1, Torque)
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assert t1 == Torque(N, N.y)
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# Bodies should be undetermined (even in case of a Particle)
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raises(ValueError, lambda: _parse_load((Particle('pa', po), N.x)))
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raises(ValueError, lambda: _parse_load((RigidBody('pa', po, N), N.x)))
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# Invalid tuple length
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raises(ValueError, lambda: _parse_load((po, N.x, po, N.x)))
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# Invalid type
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raises(TypeError, lambda: _parse_load([po, N.x]))
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