scribble Latex: add \SNumberOfAuthors{} in output

original commit: 814c974d015b647e8482a46720f0728d3b318175

collects/scribble/latex-render.rkt

@@ -120,6 +120,8 @@
                       (if (null? auths) "Empty" ""))
               (render-content (part-title-content d) d ri)
               (printf "}{~a}{" vers)
+              (unless (null? auths)
+                (printf "\\SNumberOfAuthors{~a}" (length auths)))
               (for/fold ([first? #t]) ([auth (in-list auths)])
                 (unless first? (printf "\\SAuthorSep{}"))
                 (do-render-paragraph auth d ri #t #f)

collects/scribble/scribble.tex

@@ -146,6 +146,9 @@
 \newcommand{\SAuthor}[1]{#1}
 \newcommand{\SAuthorSep}[1]{\qquad}
 
+% Useful for some styles, such as sigalternate:
+\newcommand{\SNumberOfAuthors}[1]{}
+
 % Used for parts with the 'hidden style variant:
 \newcommand{\sectionhidden}[1]{\section{#1}}
 \newcommand{\subsectionhidden}[1]{\subsection{#1}}