From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
From: "Douglas A. Gwyn" <DAGwyn@null.net>
Message-ID: <3D109DEB.9E9EB8C9@null.net>
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References: <3D104980.16646.51DF597@localhost>
Subject: Re: [9fans] Sam / text search query
Date: Wed, 19 Jun 2002 15:37:25 +0000
Topicbox-Message-UUID: b3a2a5f4-eaca-11e9-9e20-41e7f4b1d025

Andrew Simmons wrote:
> ... my brain locks up and turns to custard when faced with
> regular expressions beyond a minimal level of complexity.

The best approach for developing structural r.e.s seems to be to think
of "layers of context", first establishing the crudest approximate
context (location), then adding more r.e.s to successively refine the
context until precisely the desired region is selected.  Then invoke
the action, not forgetting that the "s" command supports \(...\) etc.
which is good for rearranging the order of pieces of the selection.
Also use sam's "u" (undo) while successively refining context to back
out any attempts that don't work as you hoped.

The following was extracted from a typical MUVES project package
Makefile; it creates source listings that include usage counts in front
of each line, great for checking test coverage:

# CAUTION: The following procedure requires Rob Pike's "sam" text
editor.
$(PCFILES):     $(HFILES) $(CFILES) $(OBJS) $(TEST).o   # $(CFILES) is
overkill
        @(      c=`echo $@ | sed 's/^P\.//'`; \
                o=`basename $$c .c`.o; \
                $(CTRACE) $$c > T.$$c; \
                $(CC) -c T.$$c; \
                mv $$o B.$$o && mv T.$$o $$o; \
                $(CC) $(LDFLAGS) -o $(TEST) $(TEST).o $(OBJS) $(TLIBES);
\
                ./$(TEST) 2> X.$$c; \
                rm -f $(TEST) T.$$o && mv B.$$o $$o; \
                grep '^ *[1-9][0-9]* ' < X.$$c \
                | sed 's/^ *\([1-9][0-9]*\).*/\1/' \
                | sort > L.$$c; \
                rm -f X.$$c; \
                ( echo ',x/t_ct_\("\\\\n *[1-9][0-9]* /{'; \
                  echo 'x/[1-9][0-9]*/p\n/\\n/p'; \
                  echo '}\nq\n' \
                ) | sam -d T.$$c | sort -u > A.$$c; \
                ( echo f P.$$c; \
                  echo ',x/^/c/ /'; \
                  uniq -c L.$$c \
                  | sed 's;^\( *[1-9][0-9]*\) \([1-9][0-9]*\);\2i/\1/;';
\
                  uniq L.$$c | comm -13 - A.$$c | sed 's;.*;&i/   0/;';
\
                  echo 'w\nq\n' \
                ) | sam -d $$c; \
                rm -f [ALT].$$c \
        )