Last one fixed. I've done the following modify:

"   ##   #   "
,"## #  #   # "
,"   # ###### "
," ###  #     "
,"   ## # ####"
,"## #  #     "
,"   # #### ##"
," ###  #     "
,"   ## #### #"
," # #@ #  #  "
," # #  #    #"
,"#    #  #   "

The @ is the added one.
Thank you for your feedback.

All what you said make sense. The first two are fixed now.

The map was

,"   ##  "
,"## #  #"
,"   # ##"
," # #  #"
," # # ##"
,"#    # "

I've changed it into

,"   ##  "
,"## #  #"
,"   # ##"
," # # ##"
," # # ##"
,"#    # "

And your answer is correct.

I'll modify the map, wait

Three problems in the test cases

1. A 7x7 test cases is actually 7 x 6

2. One case has expected solution:
   [D,D,R,R,R,R,R,D,D,L,D,L,U,L,L,D,L,D], but there is actually a shorter path:
   [D,D,R,R,R,R,R,D,D,L, L, L,L,D,L,D] which avoids a detour round a small cul-de-sac.

3. The configuration for the last two test cases (12x12) has two equally good paths, since there is an open square at 2,10 3,10 2,11 3,11; so paths:
   ...D,R,R, R,U, U,U...,
   ...D,R,R, U,R, U,U...
   both work.

I have editted the test cases to fix the size and remove the ambiguities. I hope the changes seem OK to you,

Mark

Still some bugs in the random tests of the Haskell version.

eg 1) expected: "-+14c+11x... due to a ("",-1) term

eg 2) expected: "z-6ab-9ac... but there was an (uncancelled) ("",1) term present.

Happily, random test cases are random, so two presses later I had clean green.

Working in Haskell I am getting Time: 2966ms Passed: 5 Failed: 0 Errors: 1, but there is no indication what the error is.
I need some hint about how to proceed!

Still getting this problem.

and that won't change: more than 500 completions, the tests are frozen. Nothing to do about that... :-/

Looks quite reasonable, why do you ask?

Sample tests 1 and 4 still lack second parameter, as does (at least one of) the final tests