Re: Calc; Div by 0 in solving system

[Eli Zaretskii <eliz@gnu.org>]

> From: Christopher Howard <christopher.howard@qlfiles.net>
> Date: Sun, 21 Apr 2019 07:37:47 -0800
> 
> Place this on stack with algebriac mode:
> 
> [2 * x - 3 * y + z = 5, x + y - 2 * z = 0, -x + 2 * y + 3 * z = -3]
> 
> run command 'a S x,y,z'
> 
> Receive error 'Division by zero: 1'
> 
> I enabled Debug on Error but could not find the backtrace

Here's the backtrace, obtained by setting debug-on-message to
"Division by zero":

  Debugger entered--Lisp error: "Division by zero: 1."
    message("%s%s" "Division by zero: 1." "")
    calc-explain-why((* "Division by zero" (float 1 0)) nil)
    calc-do-handle-whys()
    calc-handle-whys()
    calc-enter-result(1 "solv" (calcFunc-solve (vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z))))
    #f(compiled-function () #<bytecode 0x2000000001d6b378>)()
    calc-do(#f(compiled-function () #<bytecode 0x2000000001d6b378>) 102)
    calc-solve-for("x,y,z")
    funcall-interactively(calc-solve-for "x,y,z")
    call-interactively(calc-solve-for nil nil)
    command-execute(calc-solve-for)