ls=Re/@{a,b,c,d}
Out[]=
{Re[a],Re[b],Re[c],Re[d]}
In[]:=
sum:=
Length[ls]
∑
i=1
2
ls[[i]]
FindMinimum[sum,{#,0}&/@ls](*FindMinimumisNOTokwith[]invoke*)
FindMinimum
:Value Re[a] in search specification {Re[a],0} is not a number or array of numbers.
Out[]=
FindMinimum[sum,({#1,0}&)/@ls]
Minimize[sum,ls](*ButMinimizeisOK*)
Out[]=
{0,{Re[a]0,Re[b]0,Re[c]0,Re[d]0}}
​