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MathGroup Archive 2001

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Re:Re: metacharacters as record separators

  • To: mathgroup at smc.vnet.net
  • Subject: [mg26968] Re:[mg26935]Re: [mg26881] metacharacters as record separators
  • From: Tomas Garza <tgarza01 at prodigy.net.mx>
  • Date: Tue, 30 Jan 2001 03:38:19 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Another approach to your problem, with a more Mathematica-like flavor:

In[1]:=
ReadList["testwords.txt", Word]
Out[1]=
{"Those", "friends", "thou", "hast", "\",\"", "and", "their", 
"adoption", \
"tried", "\",\"", "grapple", "them", "unto", "thy", "soul", "with", 
"hoops", \
"of", "steel"}
In[2]:=
a1 = Characters[StringJoin @@ %]
Out[2]=
{"T", "h", "o", "s", "e", "f", "r", "i", "e", "n", "d", "s", "t", "h", 
"o", \
"u", "h", "a", "s", "t", "\"", ",", "\"", "a", "n", "d", "t", "h", "e", 
"i", \
"r", "a", "d", "o", "p", "t", "i", "o", "n", "t", "r", "i", "e", "d", 
"\"", \
",", "\"", "g", "r", "a", "p", "p", "l", "e", "t", "h", "e", "m", "u", 
"n", \
"t", "o", "t", "h", "y", "s", "o", "u", "l", "w", "i", "t", "h", "h", 
"o", \
"o", "p", "s", "o", "f", "s", "t", "e", "e", "l"}

Now locate the positions of the character you have chosen as separator 
(in this case, "h"):

In[3]:=
a2 = Position[a1, "h"] // Flatten
Out[3]=
{2, 14, 17, 28, 56, 64, 73, 74}

Then find the starting and ending positions for each of the records 
separated by "h"s:

In[4]:=
begsAndEnds = {Prepend[# + 1 & /@ a2, 1], Append[# - 1 & /@ a2, 
Length[a1]]} //
     Transpose
Out[4]=
{{1, 1}, {3, 13}, {15, 16}, {18, 27}, {29, 55}, {57, 63}, {65, 72}, {74, 

    73}, {75, 85}}

Now, select the characters which make up the separated records:

In[5]:=
Take[a1, #] & /@ begsAndEnds
Out[5]=
{{"T"}, {"o", "s", "e", "f", "r", "i", "e", "n", "d", "s", "t"}, {"o",
    "u"}, {"a", "s", "t", "\"", ",", "\"", "a", "n", "d", "t"}, {"e", 
"i",
    "r", "a", "d", "o", "p", "t", "i", "o", "n", "t", "r", "i", "e", 
"d",
    "\"", ",", "\"", "g", "r", "a", "p", "p", "l", "e", "t"}, {"e", "m", 
"u",
    "n", "t", "o", "t"}, {"y", "s", "o", "u", "l", "w", "i", "t"}, {}, 
{"o",
    "o", "p", "s", "o", "f", "s", "t", "e", "e", "l"}}

and, finally, reconstruct the records

In[6]:=
StringJoin /@ %
Out[6]=
{"T", "osefriendst", "ou", "ast\",\"andt", 
"eiradoptiontried\",\"grapplet", \
"emuntot", "ysoulwit", "", "oopsofsteel"}

Tomas Garza
Mexico City

Aaron Hirsh wrote:

> Is it possible to use metacharacters as part of record separators in
> ReadList? For example, can one separate data at each occurrence of a
> number, or at each occurrence of a character other than an uppercase
> letter?
>



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