# How TeX sets glue for \halign entries?

On p.235 of TeXbook it is said:

TeX reads an entire \halign{...} specification into its memory before typesetting anything, and it keeps track of the maximum width of each column, assuming that each column is set without stretching or shrinking the glue. Then it goes back and puts every entry into a box, setting the glue so that each box has the maximum column width.

In the first example badness is exceeded, but no warning is issued. In the second example entries are left-justified by default - why? And again, why no underfull warning is given?

\halign{\indent#&\quad#\cr
Horizontal lists&Chapter 14\cr
Vertical lists&Chapter 15\cr
Math lists&Chapter 17\cr}

\bigskip


• You probably won't get around reading the relevant parts of tex.web: github.com/TeX-Live/texlive-source/blob/… – Henri Menke Jan 15 at 5:55
• @IgorLiferenko \hbox to 1000pt{hello world} does contain glue, and the rules for its setting are described p. 77. OTOH, \hbox to 1000pt{hello} does not, and I don't know if the TeXbook describes how this case is handled. Experimentation suggests that in such a case, the box has the prescribed width and the contents is typeset flush left inside the box. – frougon Jan 16 at 13:11