@awass Yes, it would've been easy enough for solve to have been coded this way. But Maple does provide a mechanism by which you can redefine procedures to accept input for which they weren't originally intended, using very few lines of code: overload.

local solve:= overload([
   proc(V::Vector) option overload; :-solve(convert(V,set), _rest) end proc,
   :-solve
]);

You can put that in an initialization file.

@Moses Tenne The command to get 70 digits of precision is as you originally wrote:

Digits:= 70;

The 70-digit number that you entered is nonsense to Maple, and I'm baffled as to why you didn't get an error message. The part at the end, `70.*^-38, violates several rules of Maple syntax. Try

9.1256223744000000041048405246803968037257471953759678468102033290122\
7075175300672646212456658597e-38;

The interface command that I gave only affects the precision at which numbers are displayed; it has no effect on how they are stored or computed. If displayprecision is set at -1 (which I think is the default), then numbers are displayed at whatever precision they are stored.

@J4James Please don't use the title line of a Reply to hold information which should be placed in the body of the Reply. As you can see, it gets cut off, and so I can't see your error message.

convert(..., piecewise, ...) needs to be told a variable with respect to which to break into intervals. So how about this?

convert(simplify(sol), piecewise, y) assuming 1 < x, x <= y;

This doesn't seem to require any expand or collect.

@Scot Gould I already figured out the problem and Answered below, so this is a moot point, but you need to run the problematic command after issuing the trace command in order to get any useful information. The output of the trace command itself is just a list of the procedures for which you've used the trace command---pretty much worthless information. What trace does is modify the procedure so that when it is run debugging information will be printed.

You may be able to simplify out the Heun functions if you supply two initial conditions for the ODE.

Give the command

interface(displayprecision= -1);

If the value returned is not -1, then that was your problem, and it should now be corrected. If the value returned is -1, then something else is going on, and you'll need to post a worksheet. The displayprecision can be set by default from the Optionn -> Tools menu. If you need help with that, let me know.

I don't have your fieldplot command, so I can't test this, but you can: Give the command trace(RealDomain:-log, RealDomain:-ln), then do the command that fails. You might get some useful information.

@vv Yes, the memoization really speeds things up, and it's a suitable replacement for your remember table, which isn't allowed in evalhf.

I realized my error, and came back to fix it, but you noticed it first. I've corrected the Answer.

@Bryon Thanks, I found them.

It should've been designed to work correctly if one includes the option Support= -5..5 to the Distribution command. However, it doesn't. So I think that this is a design bug.

In the previous MaplePrimes, one could check the tally of a user's Posts, Answers, Replies, and favorites. That information is now gone, and I miss it. One can still see Posts, etc., but not a count of them.

@jessica99 But the equations in this Answer are not the same as those in the Question. This system is linear; the other is nonlinear. (I see now that you've changed the equations in the original Question to match those in this Answer.)

Do you have any initial conditions? I've tried various combinations, but I encounter possible singularities in the interval -5...5 for every nontrivial triple that I've tried.

Also, I'm amazed that you can compute the solution to this nonlinear system manually. Can you post your solution? Perhaps we have different concepts of what is meant by a "solution".

@Matt C Anderson Well, the name pi is certainly not obvious, so you'd have difficulty searching for it. That name, or rather the Greek letter, is the standard in number theory for the function. Having assessed your interests from your several postings, I suggest that you browse the help page of every command in the numtheory package. There's not that many. Many are related to prime numbers.

@sand15 Why would you want to suppress the Question? Your technique of examining the error messages is very useful and creative. I was just about to mention it myself.

I'd say that deleting a Question that has been Answered is frowned upon. It is extremely frowned upon by me, especially when one of the Answers is mine! However, I seem to be the only one here that speaks out vehemently against the practice, so I'm curious what others think, especially if it's their Answer that's being deleted.

The vast majority of Question-deleters that I've seen are those who want to hide the fact that they've posted their homework problem. This makes me furious when I've spent hours of effort and several days of back-and-forth discussion crafting an Answer. In the case of this Question, I don't care about my Answer, but I see no reason why your useful Reply should be deleted.

I don't want to start any bad habits among the posters. I am a moderator and you are not. My judgement is that the Question cannot be deleted. The only Answered Questions that I would allow to de deleted are those that are objectionable, illegal, nonsensical, or irrelevant to Maple. Other moderators may disagree and still have the power to delete.