<html><body><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" type="cite"><div><div>In other words, the control sequence |null_cs| with no characters to its name is always output to the world as the two primitive CSes, "\csname\endcsname". So I guess the pertinent question is, can |null_cs|'s meaning be redefined? If not, isn't it "a primitive" CS?<br><br>
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</div><div class="gmail_quote" dir="ltr">Any control sequence in TeX an be redefined. Most notably, LaTeX redefines the meaning of \end (among others).</div><div class="gmail_quote" dir="ltr"><br></div><div class="gmail_quote" dir="ltr">Being a primitive means that the control sequence executes something directly in TeX rather than expanding into a sequence of tokens. null_cs has special handling for output and its location is used for other purposes in the hash table (it’s a boundary between the single character csnames and multiple-character csnames), but it is not a primitive.</div><div class="gmail_quote" dir="ltr"><br></div><div class="gmail_quote" dir="ltr">-dh</div></body></html>