utils/unlit: adjust parser to match Report spec

The Haskell 2010 Report says that, for Latex-style Literate format,
"Program code begins on the first line following a line that begins
\begin{code}". (This is unchanged from the 98 Report)

However the unlit.c implementation only matches a line that contains
"\begin{code}" and nothing else. One consequence of this is that one
cannot suffix Latex options to the code environment. I.e., this does
not work:

\begin{code}[label=foo,caption=Foo Code]

Adjust the matcher to conform to the specification from the Report.

The Haskell Wiki currently recommends suffixing a '%' to \begin{code}
in order to deliberately hide a code block from Haskell. This is bad
advice, as it's relying on an implementation quirk rather than specified
behaviour. None-the-less, some people have tried to use it, c.f.
<https://mail.haskell.org/pipermail/haskell-cafe/2009-September/066780.html>

An alternative solution is to define a separate, equivalent Latex
environment to "code", that is functionally identical in Latex but
ignored by unlit. This should not be a burden: users are required to
manually define the code environment anyway, as it is not provided
by the Latex verbatim or lstlistings packages usually used for
presenting code in documents.

Fixes #3549.

1 files changed, 2 insertions, 2 deletions

diff --git a/utils/unlit/unlit.c b/utils/unlit/unlit.c
index 5a0e535109..2ec2af6058 100644
--- a/utils/unlit/unlit.c
+++ b/utils/unlit/unlit.c
@@ -224,9 +224,9 @@ static line readline(FILE *istream, FILE *ostream) {
     while(i > 0 && isspace(buf[i-1]))
 	i--;
     buf[i] = 0;
-    if (strcmp(buf, BEGINCODE) == 0)
+    if (strncmp(buf, BEGINCODE, LENBEGINCODE) == 0)
 	return BEGIN;
-    if (strcmp(buf, ENDCODE) == 0)
+    if (strncmp(buf, ENDCODE, LENENDCODE) == 0)
 	return END;
 #if defined(PSEUDOCODE)
     else if (strcmp(buf, BEGINPSEUDOCODE) == 0)