Search for most frequently occurring patterns in text (to replace them by macros)

Question

Are there any ready available tools for searching the most frequently occurring text patterns (word combinations, phrases) in the text you work on, so to give ideas, which ones to replace by short macros?

Answer 1

EDIT: I had implemented some version of the Lempel-Ziv-Welch algorithm, following a comment of Ryan Reich. I've now changed the code completely and I don't know if the algorithm has a name.

I fed the new code the 12 days of Christmas, as David Carlisle asked, and obtained the following result (for plain TeX)

\long\def\A#1#2{\def#1{#2}\A}\A\AG{s\par\AC\A\AB}\AH{\AE\W\X\V\T\U m\V\AD}\AA
{\C\D\E\F\G}\AB{\H\I\J\A\par\bigskip\B}\AC{\O\P\par\M\N\K\L nd}\AD{\R\S\par\Q
\A ring}\AE{\Y es danc\V}\AF{t\Z a leap\V}\B{\par On the }\C{ day of C}\D
{hristmas }\E{my true l}\F{ove gave }\G{to me\par}\H{a partrid}\I{ge in a p}\J
{ear tree.}\K{two turtl}\L{e doves\par a}\M{three fre}\N{nch hens\par}\O{four
call}\P{ing birds}\Q{five gold}\R{six geese}\S{ a laying}\T{seven swa}\U{ns a
swim}\V{ing\par}\W{eight mai}\X{ds a milk}\Y{nine ladi}\Z{en lords } \A{ }\B
first\AA\AB second\AA\K\L nd \AB third\AA\M\N\K\L nd \AB fourth\AA\AC\A\AB
fifth\AA\Q\A ring\AG sixth\AA\AD\AG seventh\AA\T\U m\V\AD\AG eighth\AA\W\X\V\T
\U m\V\AD\AG ninth\AA\AH\AG tenth\AA\AF\AH\AG eleventh\AA eleven pipers pip\V
\AF\AH\AG twelfth\AA twelve drummers drumm\V eleven pipers pip\V\AF\AH s\par
\AC\A\H\I\J\A\bye

which is 878 bytes long. This should be compared to the 767 bytes of xii.tex, which produces the same lyrics.

\RequirePackage[enable-debug]{expl3}
\ExplSyntaxOn
\cs_generate_variant:Nn \tl_replace_all:Nnn { Nxx, NV, Nxn }
\cs_generate_variant:Nn \tl_replace_once:Nnn { Nxx }
\cs_generate_variant:Nn \tl_if_in:NnT { No }
\cs_generate_variant:Nn \tl_if_eq:NNTF { cc }
\cs_generate_variant:Nn \tl_if_eq:nnTF { xx }
\cs_generate_variant:Nn \tl_if_eq:nnT { xx }
\cs_generate_variant:Nn \str_count:N { c }
\cs_generate_variant:Nn \regex_match:nnF { nV }
\cs_generate_variant:Nn \str_set:Nn { NV }
\str_new:N \l__find_prefix_str
\int_new:N \l__find_prefix_int
\tl_new:N \l__find_tl
\tl_new:N \l__find_chunks_tl
\int_step_inline:nnnn { 1 } { 1 } { 9 }
  { \seq_new:c { l__find_chunks_#1_seq } }
\int_new:N \l__find_common_int
\int_new:N \l__find_nesting_int
\tl_new:N \l__find_previous_tl
\seq_new:N \l__find_chunks_seq
\int_new:N \l__find_best_score_int
\int_new:N \l__find_macro_int
\tl_new:N \l__find_macros_tl
\tl_new:N \l__find_result_tl
\int_new:N \l__find_length_int
\int_new:N \l__find_previous_length_int
\tl_new:N \l__find_display_tl
\tl_new:N \l__find_best_chunk_tl

\cs_new_protected_nopar:Npn \dot: { \tex_message:D { . } }

\cs_new_protected:Npn \find_matches:nnN #1#2#3
  {
    % '#1' is the prefix, '#2' is the token list to study.
    %
    \__find_set_prefix:n {#1}
    \tl_set:Nn \l__find_tl { ~! #2 }
    \__find_escape_spaces:xN { \l__find_prefix_str A } \l__find_tl
    \int_set:Nn \l__find_macro_int { 1 }
    \__find_get_length:V \l__find_prefix_str
    \iow_term:x { \int_use:N \l__find_length_int }
    \int_set_eq:NN \l__find_length_int \c_max_int
    \__find_matches_aux:V \l__find_prefix_str
    \tl_replace_once:Nnn \l__find_tl { ! } { { ~ } }
    \tl_set:Nx #3
      {
        \__find_preamble:
        \exp_not:V \l__find_tl
      }
  }
\cs_new_protected:Npn \__find_escape_spaces:nN #1#2
  {
    \regex_replace_all:nnN { \cS\  } { \c{#1} } #2
    \dot:
  }
\cs_generate_variant:Nn \__find_escape_spaces:nN { x }
\cs_new_nopar:Npn \__find_preamble:
  {
    \exp_not:n { \long \def } \exp_not:c { \l__find_prefix_str A } ####1####2
      {
        \exp_not:N \def ####1{####2}
        \exp_not:c { \l__find_prefix_str A }
      }
    \exp_not:c { \l__find_prefix_str A }
  }
\cs_new_protected:Npn \__find_matches_aux:n #1
  {
    \int_set_eq:NN \l__find_previous_length_int \l__find_length_int
    \tl_set_eq:NN \l__find_previous_tl \l__find_tl
    \__find_escape_tl:nN {#1} \l__find_tl
    \int_compare:nNnTF { \tl_count:N \l__find_tl } < 9
      { \tl_set_eq:Nn \l__find_tl \l__find_previous_tl }
      {
        \__find_set_chunks:
        \__find_sort_chunks:
        \__find_common:
        \__find_best_macros:
        \__find_undefine_tmp:
        \tl_set_eq:NN \l__find_tl \l__find_result_tl
        \__find_unescape_tl:nN {#1} \l__find_tl
        \__find_get_length:n {#1}
        \iow_term:x { \int_use:N \l__find_length_int }
        \int_compare:nNnTF \l__find_length_int < \l__find_previous_length_int
          { \__find_matches_aux:n {#1} }
          {
            \iow_term:n { }
            \iow_term:x { \l__find_display_tl }
            \iow_term:n { }
            \tl_set_eq:NN \l__find_tl \l__find_previous_tl
          }
      }
  }
\cs_generate_variant:Nn \__find_matches_aux:n { V }

\cs_new_protected:Npn \__find_get_length:n #1
  {
    \tl_set_eq:NN \l__find_display_tl \l__find_tl
    \tl_replace_once:Nxx \l__find_display_tl
      { \exp_not:c { #1 A } ! }
      { ~ \exp_not:c { #1 A } {~} }
    \str_set:NV \l__find_display_tl \l__find_display_tl
    \tl_replace_all:Nxn \l__find_display_tl
      { \c_backslash_str #1 \token_to_str:N A ~ } \c_space_tl
    \tl_replace_all:Nnn \l__find_display_tl
      { ~ \c_space_tl } { ~ \exp_not:c { #1 A } }
    \dot:
    \str_set:Nx \l__find_display_tl { \__find_preamble: \l__find_display_tl }
    \tl_replace_all:Nxx \l__find_display_tl
      { \c_hash_str \c_hash_str } { \c_hash_str }
    \dot:
    \regex_replace_all:nnN
      { (\\[A-Za-z]+) \ ([A-Za-z]) }
      { \1 \ \ \2 }
      \l__find_display_tl
    \dot:
    \regex_replace_all:nnN
      { (\\[A-Za-z]+) \ }
      { \1 \c{__find_allow_break:} }
      \l__find_display_tl
    \dot:
    \iow_wrap:nnnN { \l__find_display_tl } { } { } \__find_get_length_aux:n
  }
\cs_generate_variant:Nn \__find_get_length:n { V }
\cs_new_protected:Npn \__find_get_length_aux:n #1
  {
    \int_set:Nn \l__find_length_int { \str_count:n {#1} }
    \tl_set:Nn \l__find_display_tl {#1}
  }



\cs_new_protected:Npn \__find_set_prefix:n #1
  {
    % Check that the prefix |#1| is made only of alphabetic characters.
    %
    \str_set:Nx \l__find_prefix_str {#1}
    \int_set:Nn \l__find_prefix_int { \str_count:N \l__find_prefix_str }
    \regex_match:nVF { \A\w*\Z } \l__find_prefix_str
      {
        \msg_error:nnx { find } { invalid-prefix }
          { \l__find_prefix_str }
      }
    \dot:
  }

\cs_new_protected:Npn \__find_escape_tl:nN #1#2
  {
    % During the 'study' step, we manipulate the token list |#2|
    % with all begin-group and end-group tokens replaced by a
    % control sequence built from the prefix.  We must change both
    % begin-group and end-group tokens in one pass, to avoid getting an
    % unbalanced result.  Also replace macro parameters because they
    % cannot be used as delimiters for macros.  Spaces have been
    % turned into a control sequence earlier.  At this stage, every
    % token in |#2| can be grabbed as an N-type argument.
    %
    \regex_replace_all:nnN { \cB. } { \cB\{ } #2
    \dot:
    \regex_replace_all:nnN { \cE. } { \cE\} } #2
    \dot:
    \regex_replace_all:nnN { \cP. } { \c{ #1 \# } } #2
    \dot:
    \regex_replace_all:nnN { \c[BEP]. } { \c{ #1 \0 } } #2
    \dot:
  }




\cs_new_protected_nopar:Npn \__find_set_chunks:
  {
    % Build a token list whose items are each nine consecutive tokens
    % of the original token list, in a running window.  So for instance
    % |ABCDEFGHIJKL| would lead to the following \(12\) items:
    % |ABCDEFGHI|, |BCDEFGHIJ|, |CDEFGHIJK|, |DEFGHIJKL|, |EFGHIJKL|,
    % |FGHIJKL|, |GHIJKL|, |HIJKL|, |IJKL|, |JKL|, |KL|, |L|.  The items
    % of this token list are built in an |x|-expanded loop.
    % A special case arises if the |find| token list is too short to
    % safely perform the loop: then our whole algorithm is not going to
    % do any good anyways, so we build an empty chunk list.
    %
    \tl_set:Nx \l__find_chunks_tl
      {
        \exp_after:wN \__find_set_chunks_loop:NNNNNNNNN \l__find_tl
          \q_recursion_tail \q_recursion_stop
      }
  }
\cs_new:Npn \__find_set_chunks_loop:NNNNNNNNN #1#2#3#4#5#6#7#8#9
  {
    % As usual in a TeX loop, first check for the end-loop marker (here,
    % \cs{q_recursion_tail}).  If it is reached, we fill in the last few
    % chunks (which become shorter and shorter as we go).  Otherwise,
    % add (to the token list we are building) an item containing \(9\)
    % tokens, and loop, dropping the first of the items.
    %
    \quark_if_recursion_tail_stop_do:Nn #9
      { \__find_set_chunks_end:NNNNNNNN #1 #2 #3 #4 #5 #6 #7 #8 }
    { \exp_not:n { #1 #2 #3 #4 #5 #6 #7 #8 #9 } }
    \__find_set_chunks_loop:NNNNNNNNN #2#3#4#5#6#7#8#9
  }
\cs_new:Npn \__find_set_chunks_end:NNNNNNNN #1#2#3#4#5#6#7#8
  {
    \exp_not:n
      {
        { #1 #2 #3 #4 #5 #6 #7 #8 }
        { #2 #3 #4 #5 #6 #7 #8 }
        { #3 #4 #5 #6 #7 #8 }
        { #4 #5 #6 #7 #8 }
        { #5 #6 #7 #8 }
        { #6 #7 #8 }
        { #7 #8 }
        { #8 }
      }
  }
\cs_new_protected:Npn \__find_sort_chunks:
  {
    \tl_sort:Nn \l__find_chunks_tl
      {
        \int_compare:nNnTF
          {
            \tex_strcmp:D
              { \exp_not:n {##1} }
              { \exp_not:n {##2} }
          }
          > 0
          { \sort_return_swapped: }
          { \sort_return_same: }
      }
  }

\cs_new_protected:Npn \__find_common:
  {
    \int_step_inline:nnnn { 1 } { 1 } { 9 }
      { \seq_clear:c { l__find_chunks_##1_seq } }
    \exp_after:wN \__find_common_loop:nn \l__find_chunks_tl
      \q_recursion_tail \q_recursion_tail \q_recursion_stop
    \int_step_inline:nnnn { 4 } { 1 } { 9 }
      {
        \seq_map_inline:cn { l__find_chunks_##1_seq }
          {
            \tl_if_exist:cTF { l__find_chunk_ ' \tl_to_str:n {####1} ' _tl }
              {
                \tl_put_right:cn
                  { l__find_chunk_ ' \tl_to_str:n {####1} ' _tl } { i }
              }
              {
                \cs_set_eq:cN
                  { l__find_chunk_ ' \tl_to_str:n {####1} ' _tl } \c_empty_tl
              }
          }
      }
  }

\cs_new_protected:Npn \__find_common_loop:nn #1#2
  {
    \quark_if_recursion_tail_stop:n {#2}
    \int_zero:N \l__find_common_int
    \__find_count_common_aux:nn {#1} {#2}
    \use:c { __find_common_ \int_use:N \l__find_common_int :w }
      #1 X X X X X X X X X \q_stop
    \__find_common_loop:nn {#2}
  }
\cs_new_protected:Npn \__find_count_common_aux:nn #1#2
  {
    \tl_if_empty:nF {#1}
      {
        \tl_if_empty:nF {#2}
          {
            \tl_if_eq:xxT { \tl_head:n {#1} } { \tl_head:n {#2} }
              {
                \int_incr:N \l__find_common_int
                \__find_count_common_aux:xx
                  { \tl_tail:n {#1} } { \tl_tail:n {#2} }
              }
          }
      }
  }
\cs_generate_variant:Nn \__find_count_common_aux:nn { xx }

\cs_new_eq:cN { __find_common_0:w } \use_none_delimit_by_q_stop:w
\cs_new_protected:cpn { __find_common_1:w } #1
  { \__find_common_auxii:nnw { 1 } {#1} }
\cs_new_protected:cpn { __find_common_2:w } #1#2
  { \__find_common_auxii:nnw { 2 } { #1 #2 } }
\cs_new_protected:cpn { __find_common_3:w } #1#2#3
  { \__find_common_auxii:nnw { 3 } { #1 #2 #3 } }
\cs_new_protected:cpn { __find_common_4:w } #1#2#3#4
  { \__find_common_auxii:nnw { 4 } { #1 #2 #3 #4 } }
\cs_new_protected:cpn { __find_common_5:w } #1#2#3#4#5
  {
    \dot:
    \__find_common_auxii:nnw { 5 } { #1 #2 #3 #4 #5 }
  }
\cs_new_protected:cpn { __find_common_6:w } #1#2#3#4#5#6
  { \__find_common_auxii:nnw { 6 } { #1 #2 #3 #4 #5 #6 } }
\cs_new_protected:cpn { __find_common_7:w } #1#2#3#4#5#6#7
  { \__find_common_auxii:nnw { 7 } { #1 #2 #3 #4 #5 #6 #7 } }
\cs_new_protected:cpn { __find_common_8:w } #1#2#3#4#5#6#7#8
  { \__find_common_auxii:nnw { 8 } { #1 #2 #3 #4 #5 #6 #7 #8 } }
\cs_new_protected:cpn { __find_common_9:w } #1#2#3#4#5#6#7#8#9
  { \__find_common_auxii:nnw { 9 } { #1 #2 #3 #4 #5 #6 #7 #8 #9 } }
\cs_new_protected:Npn \__find_common_auxii:nnw #1#2#3 \q_stop
  {
    \int_zero:N \l__find_nesting_int
    \tl_map_inline:nn {#2}
      {
        \str_case_e:nn { \exp_not:n {##1} }
          {
            { \exp_not:c { \l__find_prefix_str \c_left_brace_str } }
              { \int_incr:N \l__find_nesting_int }
            { \exp_not:c { \l__find_prefix_str \c_right_brace_str } }
              {
                \int_compare:nNnF \l__find_nesting_int > 0
                  { \use_none_delimit_by_q_stop:w }
                \int_decr:N \l__find_nesting_int
              }
          }
      }
    \int_compare:nNnF \l__find_nesting_int = 0
      { \use_none_delimit_by_q_stop:w }
    \seq_put_right:cn { l__find_chunks_#1_seq } {#2}
    \use_none_delimit_by_q_stop:w
    \q_stop
  }

\cs_new_protected_nopar:Npn \__find_best_macros:
  {
    \tl_clear:N \l__find_macros_tl
    \tl_clear:N \l__find_result_tl
    \__find_best_macros_aux:
    \tl_put_left:NV \l__find_result_tl \l__find_macros_tl
  }
\cs_new_protected:Npn \__find_best_macros_aux:
  {
    \exp_after:wN \__find_best_macros_auxii:NNNNNNNNN \l__find_tl
      \q_nil \q_nil \q_nil \q_nil \q_nil \q_nil \q_nil \q_nil \q_nil \q_stop
    \tl_if_empty:NF \l__find_tl { \__find_best_macros_aux: }
  }
\cs_new_protected:Npn \__find_best_macros_auxii:NNNNNNNNN #1#2#3#4#5#6#7#8#9
  {
    \int_zero:N \l__find_best_score_int
    \tl_clear:N \l__find_best_chunk_tl
    \tl_map_inline:nn
      {
        {#1} {#1#2} {#1#2#3} {#1#2#3#4} {#1#2#3#4#5} {#1#2#3#4#5#6}
        {#1#2#3#4#5#6#7} {#1#2#3#4#5#6#7#8} {#1#2#3#4#5#6#7#8#9}
      }
      {
        \int_compare:nNnT
          { \__find_score:n {##1} } > \l__find_best_score_int
          {
            \tl_set:Nn \l__find_best_chunk_tl {##1}
            \int_set:Nn \l__find_best_score_int
              { \__find_score:n {##1} }
          }
      }
    \tl_if_empty:NF \l__find_best_chunk_tl
      {
        \int_incr:N \l__find_macro_int
        \tl_put_right:Nx \l__find_macros_tl
          {
            \exp_not:c
              { \l__find_prefix_str \int_to_Alph:n { \l__find_macro_int } }
            { \exp_not:V \l__find_best_chunk_tl }
          }
        \use:x
          {
            \exp_not:n { \tl_replace_all:NVn \l__find_tl \l__find_best_chunk_tl }
              { \exp_not:c { \l__find_prefix_str \int_to_Alph:n { \l__find_macro_int } } }
          }
        \dot:
      }
    \tl_put_right:Nx \l__find_result_tl { \tl_head:N \l__find_tl }
    \tl_set:Nx \l__find_tl { \tl_tail:N \l__find_tl }
    \use_none_delimit_by_q_stop:w
  }
\cs_new:Npn \__find_score:n #1
  {
    % Turning ####1 into a length (p+2) macro
    % (e.g. |\<prefix>A|) saves this number of chars.
    % Good if non-negative.
    \cs_if_exist:cTF { l__find_chunk_ ' \tl_to_str:n {#1} ' _tl }
      {
        \int_eval:n
          {
            \tl_count:c { l__find_chunk_ ' \tl_to_str:n {#1} ' _tl }
            * ( \str_count:n {#1} - 3 - \l__find_prefix_int )
            - 2 * \l__find_prefix_int - 9
          }
      }
      { -1 }
  }

\cs_new_protected:Npn \__find_undefine_tmp:
  {
    \int_step_inline:nnnn { 4 } { 1 } { 9 }
      {
        \seq_map_inline:cn { l__find_chunks_##1_seq }
          { \cs_undefine:c { l__find_chunk_ ' \tl_to_str:n {####1} ' _tl } }
      }
  }

\cs_new_protected:Npn \__find_unescape_tl:nN #1#2
  {
    \regex_replace_all:nnN { \c{#1\{} } { \cB\{ \cE\? } #2
    \dot:
    \regex_replace_all:nnN { \c{#1\}} } { \cB\? \cE\} } #2
    \dot:
    \regex_replace_all:nnN { \c[BE]\? } { } #2
    \dot:
    \regex_replace_all:nnN { \c{#1\#} } { \cP\# } #2
    \dot:
  }

\cs_if_exist:NTF \iow_allow_break:
  { \cs_new:Npn \__find_allow_break: { \iow_allow_break: } }
  { \cs_new:Npn \__find_allow_break: { ~ } }

\msg_new:nnn { find } { invalid-prefix }
  { The~prefix~used,~'#1',~must~be~made~of~letters. }

\cs_set_protected:Npn \FindMatches #1#2
  {
    \find_matches:nnN {#1} {#2} \l_tmpa_tl
    \tl_use:N \l_tmpa_tl
  }
\ExplSyntaxOff

% Set up some basic things to behave a bit like plain TeX.
%
\documentclass{article}
\begin{document}
\setlength{\parindent}{0pt}
\def\bye{\end{document}}
%
% End of setup.

\FindMatches{}{% Let's go!

On the first day of Christmas my true love gave to me\par
a partridge in a pear tree.

\bigskip

On the second day of Christmas my true love gave to me\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the third day of Christmas my true love gave to me\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the fourth day of Christmas my true love gave to me\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the fifth day of Christmas my true love gave to me\par
five gold rings\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the sixth day of Christmas my true love gave to me\par
six geese a laying\par
five gold rings\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the seventh day of Christmas my true love gave to me\par
seven swans a swimming\par
six geese a laying\par
five gold rings\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the eighth day of Christmas my true love gave to me\par
eight maids a milking\par
seven swans a swimming\par
six geese a laying\par
five gold rings\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the ninth day of Christmas my true love gave to me\par
nine ladies dancing\par
eight maids a milking\par
seven swans a swimming\par
six geese a laying\par
five gold rings\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the tenth day of Christmas my true love gave to me\par
ten lords a leaping\par
nine ladies dancing\par
eight maids a milking\par
seven swans a swimming\par
six geese a laying\par
five gold rings\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the eleventh day of Christmas my true love gave to me\par
eleven pipers piping\par
ten lords a leaping\par
nine ladies dancing\par
eight maids a milking\par
seven swans a swimming\par
six geese a laying\par
five gold rings\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.

\bigskip

On the twelfth day of Christmas my true love gave to me\par
twelve drummers drumming\par
eleven pipers piping\par
ten lords a leaping\par
nine ladies dancing\par
eight maids a milking\par
seven swans a swimming\par
six geese a laying\par
five gold rings\par
four calling birds\par
three french hens\par
two turtle doves\par
and a partridge in a pear tree.
\bye
}

Answer 2

What I present is a total kludge, stealing things from my titlecaps package. So the format is not optimal, but it might give a place from which to proceed. Nice thing is that punctuation is screened out of the search in the target-text.

When a search-string and target-text (not exceeding one paragraph) is passed to the \seekphrase, it will output where each word of the search-phrase appears in the target-text. I output it as a pair "target-location:search-word-index". To try to make sense of it, I output a [ before a search-word-index=1 match and a ]after a search-word-index=n match. Thus to qualify as a matching "phrase" in, for example, a 3-word search, the output would have to contain an instance of something like [214:1 215:2, 216:3]

Further refinement is clearly possible, but it would take more time than I have at the moment.

\documentclass{article}
\usepackage{titlecaps}
\usepackage{lipsum}
\makeatletter
\renewcommand\seek@lcwords{%
\kill@punct%
  \setcounter{word@count}{0}%
  \whiledo{\value{word@count} < \narg}{%
    \addtocounter{word@count}{1}%
\protected@edef\current@word{\csname arg\roman{word@count}\endcsname}%
    \def\found@word{F}%
    \setcounter{lcword@index}{0}%
    \expandafter\def\csname%
            found@word\roman{word@count}\endcsname{F}%
    \whiledo{\value{lcword@index} < \value{lc@words}}{%
      \addtocounter{lcword@index}{1}%
      \protected@edef\current@lcword{%
            \csname lcword\roman{lcword@index}\endcsname}%
%% THE FOLLOWING THREE LINES ARE FROM DAVID CARLISLE
  \protected@edef\tmp{\noexpand\scantokens{\def\noexpand\tmp%
   {\noexpand\ifthenelse{\noexpand\equal{\current@word}{\current@lcword}}}}}%
  \tmp\ifhmode\unskip\fi\tmp
%%
      {\expandafter\def\csname%
            found@word\roman{word@count}\endcsname{T}%
\ifthenelse{\equal{\value{lcword@index}}{1}}{[}{}%
\arabic{word@count}:\arabic{lcword@index}%
\ifthenelse{\equal{\value{lcword@index}}{\value{lc@words}}}{]}{ }%
       \setcounter{lcword@index}{\value{lc@words}}}%
      {}%
    }%
  }%
\restore@punct%
}
\let\getargsC\get@argsC

\newcommand\seekphrase[2]{%
  Seeking phrase ``#1'':\\%
  \Addlcwords{#1}%
  \redefine@tertius%
  \getargsC{#2}%
  \seek@lcwords%
  \Resetlcwords%
  \par%
}
\makeatother

\begin{document}

\lipsum[1]
\lipsum[1]

\def\x{%
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut
purus elit, vestibulum ut, placerat ac, adipiscing vitae, felis.
Curabitur dictum gravida mauris. Nam arcu libero, nonummy eget,
consectetuer id, vulputate a, magna.  Donec vehicula augue eu neque.
Pellentesque habitant morbi tristique senectus et netus et malesuada
fames ac turpis egestas. Mauris ut leo. Cras viverra metus rhoncus sem.
Nulla et lectus vestibulum urna fringilla ultrices.  Phasellus eu tellus
sit amet tortor gravida placerat. Integer sapien est, iaculis in,
pretium quis, viverra ac, nunc. Praesent eget sem vel leo ultrices
bibendum.  Aenean faucibus.  Morbi dolor nulla, malesuada eu, pulvinar
at, mollis ac, nulla. Curabitur auctor semper nulla. Donec varius orci
eget risus. Duis nibh mi, congue eu, accumsan eleifend, sagittis quis,
diam. Duis eget orci sit amet orci dignissim rutrum.
%
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut
purus elit, vestibulum ut, placerat ac, adipiscing vitae, felis.
Curabitur dictum gravida mauris. Nam arcu libero, nonummy eget,
consectetuer id, vulputate a, magna.  Donec vehicula augue eu neque.
Pellentesque habitant morbi tristique senectus et netus et malesuada
fames ac turpis egestas. Mauris ut leo. Cras viverra metus rhoncus sem.
Nulla et lectus vestibulum urna fringilla ultrices.  Phasellus eu tellus
sit amet tortor gravida placerat. Integer sapien est, iaculis in,
pretium quis, viverra ac, nunc. Praesent eget sem vel leo ultrices
bibendum.  Aenean faucibus.  Morbi dolor nulla, malesuada eu, pulvinar
at, mollis ac, nulla. Curabitur auctor semper nulla. Donec varius orci
eget risus. Duis nibh mi, congue eu, accumsan eleifend, sagittis quis,
diam. Duis eget orci sit amet orci dignissim rutrum.
}

\seekphrase{et}{\x}

\seekphrase{et netus}{\x}

\seekphrase{bibendum Aenean}{\x}

\seekphrase{eget sem vel}{\x}

\end{document}