[OS X TeX] ligatures

[Jonathan Kew]

On 17 Jul 2010, at 20:51, Dr. Clea F. Rees wrote:

> If I typeset the following:
> ---ligature test file---
> % !TEX TS-program = pdflatex
> % !TEX encoding = UTF-8 Unicode
> \listfiles
> \documentclass[12pt]{article}
> \title{Brief Article}
> \author{The Author}
> 
> \begin{document}
> 
> f{}f ff shelf{}ful f{}f ff\\
> 
> \end{document}
> ---end test file---
> then I get (what is to me) unexpected output.
> 
> Expected:
> no-lig-ff lig-ff shel-no-lig-ff-ul no-lig-ff lig-ff
> 
> Actual:
> no-lig-ff lig-ff shel-lig-ff-ul no-lig-ff lig-ff
> 
> Why does TeX ignore the instruction not to use the ff ligature in
> 'shelful' when a line break occurs afterwards? And why does it
> nonetheless accept the instruction if the f-no-lig-f is typeset in
> isolation?

Because it attempted hyphenation, while looking for (and failing to find) a better way to line-break the paragraph.

{} is not a reliable way to prevent a ligature. Use {\kern0pt} or possibly \/. See The TeXbook, p.306.

JK