diff: variable must not be a number; found: | bug??

>   From: Wolfgang Lindner <LindnerW at t-online.de>
>   Date: Tue, 19 Nov 2013 08:29:16 +0100
>
>   Leo,
>
>   I think you have vergotten to tell us,
>   what the input (%i5) is.
>   Could you please tell us this input.
>
>   Sincerely
>   Wolfgang

Wolfgang, I was copying Maxima code into the Maxima session. The two
input lines are bunched together in the original transcript. Here is
an edited transcript that makes the input and output clearer.

(%i4)
implicitdiff(cp_base,%lambda,sigma_1);

(%o4) 'diff(%lambda,sigma_1,1) = -((%lambda*m_3*sigma_2-%lambda*m_3)
                               *s_0*s_1*s_2*s_3
                               +(%lambda^2*m_3-%lambda^2*m_3*sigma_2)
                                *s_0*s_1*s_2)
                               /(3*%lambda^2*s_3^2
                                +(((m_3*sigma_1-m_3)*sigma_2-m_3*sigma_1+m_3)
                                 *s_0*s_1*s_2
                                 -8*%lambda^3)
                                 *s_3
                                +((2*%lambda*m_3-2*%lambda*m_3*sigma_1)
                                 *sigma_2
                                 +2*%lambda*m_3*sigma_1-2*%lambda*m_3)
                                 *s_0*s_1*s_2+5*%lambda^4)
(%i5)
subst([s_0=0.35,s_1=0.60,s_2=0.80,s_3=0.90,m_3=1.25,%lambda=1.08,sigma_1=0,sigma_2=0],rhs(%));

(%o5) -.1350578819494058

Leo