#4693 Makelist completely fails with simp:false

[Christopher Sangwin]

The makelist function completely fails with simp:false. This is a minimal example:

simp:false;
makelist(k,k,1,5);

This is a real problem for users of STACK (https://stack-assessment.org/) who need to generate un-simplified expressions.

[Christopher Sangwin]

I think this should be fairly simple to fix, by "simplifying" the numbers before testing. I'm suggesting we don't go as far as using this.

(defun interval2 (i s d)
  (do ((nn i (let (($simp t))
               (meval `((mplus) ,s ,nn))))
       (m 0 (1+ m))
       (ans))
      ((> m d) (nreverse ans))
    (push nn ans)))

If you want the values of the variables simplified, you can always use

makelist(ev(k,simp)^2,k,1,4);

[Christopher Sangwin]

I've proposed a fix here: https://sourceforge.net/u/sangwincsf/maxima/ci/0bd4236f66994f5cf2191be693fa4154e511f5d7

[Raymond Toy]

What's wrong with telling people to use 'makelist(k,k,1,5)?

I'm not really keen on hacking on things so that simp:false will work in some specific cases. (But I never turn that off, so I'm not a good judge on what simp:false should or should not do.)

[Christopher Sangwin]

Sorry, I should have explained the use-case more clearly. The goal is to create un-simplified objects, e.g. for the student to simplify themselves.

We use simp:false all the time when using Maxima for online assessment. I appreciate that's unusual to CAS users who always want the answer to a calculation!

'makelist(k,k,1,5) returns the makelist unevaluated. We would like things like

makelist(ev(k,simp)+2,k,1,5) to return [1+2,2+2,3+2,4+2,5+2]. The only reason makelist currently fails is because the error trapping does not recognize the un-simplified numbers.

We're not proposing simp:falsewill work in some specific cases, rather we'd like comprehensive support for simp:false. This particular example (with makelist) comes up a lot. Our long-standing work around is to use something like

map(lambda([ex], ex+2), ev(makelist(k,k,1,5),simp))

which is rather artificial! I hope this makes sense.

(For anyone new to STACK, which uses Maxima, the project website is herehttps://stack-assessment.org/ The Maxima community would be very welcome at one of our conferences or meetings. Thanks for Maxima, it's great. I'm making this suggestion as a genuine improvement).

[Leo Butler]

Following my post below, the easy and natural way to make your example work is like this:

(%i1) l : makelist(Plus(k,2),k,1,5);
(%o1)    [Plus(1, 2), Plus(2, 2), Plus(3, 2), Plus(4, 2), Plus(5, 2)]
(%i2) lsimp : subst(Plus="+", l);
(%o2)                           [3, 4, 5, 6, 7]

and then

(%i3) texput(Plus,lambda([expr],printf(false,"~{~a~^+~}",map(tex1,args(expr)))))$
(%i4) tex(l);
$$\left[ 1+2 , 2+2 , 3+2 , 4+2 , 5+2 \right] $$

We can define more complicated simplifiers for the Plus operator (or analogues), but subst will work 99% of the time for the problems in STACK.

And, if your users prefer an infix operator instead of the prefix operator Plus, that is no problem:

infix("⨹"); /* or ++ or ... */
texput("⨹",lambda([expr],tex1(subst("⨹"=Plus,expr))));

For example,

```
(%i20) l : makelist(k ⨹ 2 ⨹ Exp(k,3),k,1,5);

(%o20) [(1 ⨹ 2) ⨹ Exp(1, 3), (2 ⨹ 2) ⨹ Exp(2, 3), (3 ⨹ 2) ⨹ Exp(3, 3),
(4 ⨹ 2) ⨹ Exp(4, 3), (5 ⨹ 2) ⨹ Exp(5, 3)]

(%i21) tex(l);
$$\left[ 1+2+{1}^{3} , 2+2+{2}^{3} , 3+2+{3}^{3} , 4+2+{4}^{3} , 5+2+{5}^{3}
\right] $$

(%i22) lsimp : subst(["⨹"="+", Exp="^"], l);
(%o22) [4, 12, 32, 70, 132]

```

[Leo Butler]

I agree with Ray about simp:false. Besides, Maxima provides a more powerful way to deal with this problem: noun operators. For example, I want to produce a list of (unsimplified) squares:

l : makelist(Exp(k,2),k,1,5);
lsimp : subst(Exp="^",l);

In 1d display:

(%i1) l : makelist(Exp(k,2),k,1,5);
(%o1) [Exp(1,2),Exp(2,2),Exp(3,2),Exp(4,2),Exp(5,2)]
(%i2) lsimp : subst(Exp="^",l);
(%o2) [1,4,9,16,25]

If I want to make the display look nice in TeX, I can add a printer for TeX:

(%i3) texput(Exp,lambda([expr],printf(false,"{~a}^{~a}",tex1(first(expr)),tex1(second(expr))))) $

and then

(%i4) tex(l);
$$\left[ {1}^{2} , {2}^{2} , {3}^{2} , {4}^{2} , {5}^{2} \right] $$

This is, I think, a much more robust way to deal with the problem of generating "unsimplified" expressions. Too much of Maxima's capabilities cease to function when the simplifier is turned off. I don't think this is a bug, because Maxima provides a means to create unsimplified or partially simplified expressions even when the simplifier is on.

[Stavros Macrakis]

makelist uses the simplifier to perform arithmetic in order to cover all
kinds of number, e.g.,

makelist(i,i,2/3,5.0b0) => [2/3,5/3,8/3,11/3,14/3]

makelist(i,i,-2.1b0,0,7/8) => [-2.1b0, -1.225b0, -3.5b-1]

As an incidental bonus, it handles some non-numeric cases:

makelist(i,i,n,n+2) => [n, n+1, n+2]
makelist(i,i,sqrt(%e),%pi) => [sqrt(%e), sqrt(%e)+1]

I say incidental because it doesn't handle the general symbolic case,
where the termination condition requires symbolic comparisons. But I don't
think anyone needs or wants that case (in any case is is very weak).

Is it reasonable to bind simp to t while evaluating incrementation and
termination? I guess it doesn't interfere with the usual reasons that
people use simp:false.

         -s

On Tue, Mar 31, 2026 at 12:12 PM Leo Butler via Maxima-bugs maxima-bugs@lists.sourceforge.net wrote:

I agree with Ray about simp:false. Besides, Maxima provides a more
powerful way to deal with this problem: noun operators. For example, I want
to produce a list of (unsimplified) squares:

l : makelist(Exp(k,2),k,1,5);lsimp : subst(Exp="^",l);

In 1d display:

(%i1) l : makelist(Exp(k,2),k,1,5);
(%o1) [Exp(1,2),Exp(2,2),Exp(3,2),Exp(4,2),Exp(5,2)]
(%i2) lsimp : subst(Exp="^",l);
(%o2) [1,4,9,16,25]

If I want to make the display look nice in TeX, I can add a printer for
TeX:

(%i3) texput(Exp,lambda([expr],printf(false,"{~a}^{~a}",tex1(first(expr)),tex1(second(expr))))) $

and then

(%i4) tex(l);$$\left[ {1}^{2} , {2}^{2} , {3}^{2} , {4}^{2} , {5}^{2} \right] $$

This is, I think, a much more robust way to deal with the problem of
generating "unsimplified" expressions. Too much of Maxima's capabilities
cease to function when the simplifier is turned off. I don't think this is
a bug, because Maxima provides a means to create unsimplified or partially
simplified expressions even when the simplifier is on.

---

[bugs:#4693] https://sourceforge.net/p/maxima/bugs/4693/ Makelist
completely fails with simp:false

Status: open
Group: None
Created: Tue Mar 31, 2026 09:31 AM UTC by Christopher Sangwin
Last Updated: Tue Mar 31, 2026 04:04 PM UTC
Owner: nobody

The makelist function completely fails with simp:false. This is a minimal
example:

simp:false;makelist(k,k,1,5);

This is a real problem for users of STACK (https://stack-assessment.org/)
who need to generate un-simplified expressions.

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