feat(ik): IKSolution is a sequence of the rows of q, true if successful

[petercorke]

Summary

IKSolution now behaves as a sequence of the joint vectors of the poses it holds, so a solution for a single pose and for a trajectory are used the same way (numeric or analytic):

• len(sol) is the number of poses: 1 for a single pose, N for a trajectory, 0 if q is None
• for q in sol, sol[i] and slices give the rows of q. sol[i] is np.atleast_2d(sol.q)[i], an array and not an IKSolution, because success, residual and reason apply to the whole solution
• bool(sol) is sol.success
• sol.astuple() returns the six fields as a tuple
• printing: a trajectory shows the number of poses and a long q is abbreviated (first three and last two poses); the residual of a failed solution is no longer rounded to zero; an analytic solution shows its residual if it has one. The single pose format is otherwise unchanged.

This prepares the analytic IK work, which needs one result type for single poses, trajectories and "all solutions of one pose".

Incompatible change

Iterating an IKSolution used to give its six fields (added in 1.4.2 for code written against the old bare tuple), so q, success, ... = sol and sol[1] no longer work. Use the attributes or sol.astuple(). This is a small incompatible change, committed as a feat (no major version bump), as is usual for such changes here.

I searched for uses of the old form in this repo (code, docstrings, .rst, notebooks, examples), the wiki, and the RVC3-python, MVTB, bdsim and rvc-* repos. The only ones were in tests, the __main__ demo at the bottom of IK.py, and one README snippet (which also showed an out-of-date result format), all updated here. External users are unknown.

Notes

• the pinned print tests for analytic solutions used an arbitrary residual=3, so they now expect it to be shown
• the class docstring has a runnable runblock example, and ik.rst has one sentence pointing to it (kept to a single line away from the table so it merges cleanly with fix(ik): trajectory residual is the maximum, and document trajectory behaviour #712)
• trial merges with fix(ik): trajectory residual is the maximum, and document trajectory behaviour #712, refactor(ik): joint limit helpers as module-level functions #713, fix(ik): Robot.ikine_* accept an (N, 4, 4) array of poses #714, fix(puma): self-contained ikine_a with trajectory and failure handling; deprecate ikine_6s #715 and feat(robot): jtraj takes joint coordinates only, SE3 arguments raise #716 are clean

Test plan

• tests/test_IK.py, test_ik_joint_limits.py, test_Robot.py, test_DHRobot.py, test_ETS.py, test_trajectory.py: 473 passed
• new tests: single pose is one row, trajectory rows / slices / index arrays / IndexError, NumPy sees the rows, q is None is empty, bool(sol) is success (also with rows present), astuple, a real solver trajectory, and the print cases (trajectory, long trajectory abbreviated, failed residual not rounded, analytic without a residual)
• the five ik_* tests that read success with sol[1] and the old tuple tests are rewritten to use attributes
• CI

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[codacy-production]

Up to standards ✅

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🟢 Metrics 27 complexity · -2 duplication

Metric	Results
Complexity	27
Duplication	-2

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (acc6842) to head (6d4fc42).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/roboticstoolbox/robot/IK.py	0.00%	36 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #717   +/-   ##
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  Coverage   0.00%   0.00%           
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  Files        143     143           
  Lines      14269   14293   +24     
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- Misses     14269   14293   +24     

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