On Wolfram Cloud, there are some bugs. Like this one:
In[14]:= a=first;
b=second;
f=head;
Trace[f[a,b]]
Out[17]= {}
In[8]:= $Version
Out[8]= 12.1.2 for Linux x86 (64-bit) (September 9, 2020)
On Wolfram Cloud, there are some bugs. Like this one:
In[14]:= a=first;
b=second;
f=head;
Trace[f[a,b]]
Out[17]= {}
In[8]:= $Version
Out[8]= 12.1.2 for Linux x86 (64-bit) (September 9, 2020)