bug#40155: 27.0.90; `math-truc' called with `nil' during `calc-graph-fast' call

[Narendra Joshi <narendraj9@gmail.com>]

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Hi Mattias,

Thanks for the explanation. The patch fixes the original issue and
other calculations I tried didn't seem to be affected.

I found out that `calc` doesn't set the LineStyles (and maybe
PointStyles as well but I am not sure how to hand those over to
gnuplot command) properly for the gnuplot command. I think it should
do something similar to the patch I have attached.

Best,
Narendra

On Fri, Mar 27, 2020 at 6:37 PM Mattias Engdegård <mattiase@acm.org> wrote:
>
> Thanks for the report. Explanation:
>
> The graph code does
>
> (and (Math-num-integerp lstyle) (math-trunc lstyle))
>
> but Math-num-integerp returns true for nil, and math-trunc returns the argument if it satisfies Math-integerp, which used to return true for nil as well. Thus, the expression above 'works' (ie, returns nil) when lstyle is nil as well.
>
> However, Math-integerp was changed in Emacs 27 to use native bignums, and no longer returns true for nil, resulting in the error. Changing Math-num-integerp to return false for nil would make the code work again, this time in the way originally intended.
>
> Would you try this patch? (Please try various other operations as well, in case the change had unintended consequences.)
>

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From 1f40f23df71946fbed75881c6dca54eda94702c2 Mon Sep 17 00:00:00 2001
From: Narendra Joshi <narendraj9@gmail.com>
Date: Fri, 27 Mar 2020 21:51:09 +0100
Subject: [PATCH] Fix setting linestyle in calc-graph fns.

---
 lisp/calc/calc-graph.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lisp/calc/calc-graph.el b/lisp/calc/calc-graph.el
index 4cdfdbd4b9..be0e133c9c 100644
--- a/lisp/calc/calc-graph.el
+++ b/lisp/calc/calc-graph.el
@@ -1139,7 +1139,7 @@ calc-graph-set-styles
                     (if (and lstyle (> lstyle 0)) (int-to-string lstyle) "1")
                     " " (int-to-string pstyle))
           (if (and lstyle (> lstyle 0))
-              (insert " " (int-to-string lstyle)))))))
+              (insert " ls " (int-to-string lstyle)))))))
   (calc-graph-view-commands))
 
 (defun calc-graph-zero-x (flag)
-- 
2.20.1