I got the following question wrong on a test, but he didn't offer correct answers, and now the semester is over.
Does anyone know this?
I would love to know where I went wrong.
The question was to draw a parse tree for the following expression: (a+b)*(c+d) - 4
I would draw it something like this:
-
/ \
* 4
/ \
+ +
/ \ / \
a b c d
(Pardon my ASCII art skills)
Related
How can I draw the parse tree for 4*(3+5*7).
The sum of the above expression is 152.
first 5*7=35, then 35+3=38, finally 38*4=152.
I am not sure about what I drew. Please Help. Many thanks!
Something like this, perhaps? (pardon my crappy ASCII art skills)
*
/ \
4 (
/ \
+ )
/ \
3 *
/ \
5 7
(an AST would omit the parenthesis, not required for evaluation)
First time markdown user (and LaTex novice).
I'm trying to insert inline formulas using single $ as I have seen demonstrated in several places, including the R Markdown Reference Guide - but it's not working.
inline equation test: $x \leq 5 $ not working
is simply output as
"inline equation test: $x 5 $ not working"
It works fine using $$ to create a new line, but any tips how to get it working inline would be much appreciated.
And as so often happens, as soon as I ask a question, the answer comes to me.
inline equation test: $x \leq 5 $ not working
has a space before the closing $ and does not work.
inline equation test: $x \leq 5$ not working
has the space deleted and works just fine.
I'm totally new to AWK, however I think this is the best way to solve my problem and a good time to learn AWK.
I am trying to read a large data file that is created by a simulation program. The output is made to be readable by humans, so its formatting isn't very consistent. An example of the output is in this image
http://i.imgur.com/0kf8l.png
I need a way to find a line like "He 2 4686A -2.088 0.0071", by specifying the "He 2 4686A" part and get the following two numbers. The problem is the line "He 2 4686A -2.088 0.0071" can appear anywhere in the table.
I know how to find the entry "He 2 4686A", but I don't know which of the 4 columns it's in. So I don't know how to address the values that follow it.
A command that lets me just read the next two words, or tells me the location of the pattern once a match is found will both help.
/He 2 4686A/ finds the line
Ca A 3970A -0.900 0.1100 He 2 4686A -2.088 0.0071 S 3 18.67m -0.371 0.3721 Ar 4 444.7A -2.124 0.0066
Any help is appreciated.
First step should be to bring what seems to be 4 columns of records into a 1-column format...then its easy with awk because you can then filter for the first 5 fields - like:
echo "He 2 4686A -2.088 0.0071" | \
awk '$1 == "He" && $2 == 2 && $3 == "4686A" {print $4, $5}'
which gives
-2.088 0.0071
So, for me, the only challenge is to transform your data to one-column format...And from the picture that look simple because it seems that the columns have a fixed length which you can count.
Assuming that your column-width is 30 characters (difficult to tell from a picture, beware of tabs) and you data is in input_file, then you could first "cut" the data into 4 columns and then pipe the output to another awk-process
awk '{
print substr($0,1,30)
print substr($0,31,30)
print substr($0,61,30)
print substr($0,91,30)
}' input_file | \
awk '$1 == "He" && $2 == 2 && $3 == "4686A" {print $4, $5}'
If you really just need the next two numbers behind an anchor then I would say the grep-solution from Costa is best for you, however this gives you the possibility to implement further logic...
If you're not dead set on using awk, grep would be the easiest way...
egrep -o "He 2 4686A \-?[0-9.]+ \-?[0-9.]+" output.txt
EDIT: The above would work only if the spacing was done with a whitespace, which doesn't seem to be your case. In order to handle tabs and/or repeating whitespaces...
egrep -o "He[ \t]+2[ \t]+4686A[ \t]+\-?[0-9.]+[ \t]+\-?[0-9.]+" output.txt
If I run grep -C 1 match over the following file:
a
b
match1
c
d
e
match2
f
match3
g
I get the following output:
b
match1
c
--
e
match2
f
match3
g
As you can see, since the context around the contiguous matches "match2" and "match3" overlap, they are merged. However, I would prefer to get one context description for each match, possibly duplicating lines from the input in the context reporting. In this case, what I would like is:
b
match1
c
--
e
match2
f
--
f
match3
g
What would be the best way to achieve this? I would prefer solutions which are general enough to be trivially adaptable to other grep options (different values for -A, -B, -C, or entirely different flags). Ideally, I was hoping that there was a clever way to do that just with grep....
I don't think it is possible to do that using plain grep.
the sed construct below works to some extent, now I only need to figure out how to add the "--" separator
$ sed -n -e '/match/{x;1!p;g;$!N;p;D;}' -e h log
b
match1
c
e
match2
f
f
match3
g
I don't think this is possible using plain grep.
Have you ever used Python? In my opinion it's a perfect language for such tasks (this code snippet will work for both Python 2.7 and 3.x):
with open("your_file_name") as f:
lines = [line.rstrip() for line in f.readlines()]
for num, line in enumerate(lines):
if "match" in line:
if num > 0:
print(lines[num - 1])
print(line)
if num < len(lines) - 1:
print(lines[num + 1])
if num < len(lines) - 2:
print("--")
This gives me:
b
match1
c
--
e
match2
f
--
f
match3
g
I'd suggest to patch grep instead of working around it. In GNU grep 2.9 in src/main.cpp:
933 /* We print the SEP_STR_GROUP separator only if our output is
934 discontiguous from the last output in the file. */
935 if ((out_before || out_after) && used && p != lastout && group_separator)
936 {
937 PR_SGR_START_IF(sep_color);
938 fputs (group_separator, stdout);
939 PR_SGR_END_IF(sep_color);
940 fputc('\n', stdout);
941 }
942
A simple additional flag would suffice here.
Edit: Well, d'oh, it is of course not THAT simple since grep would not reproduce the context, just add a few more separators. Due to the linearity of grep, the whole patch is probably not that easy. Nevertheless, if you have a good case for the patch, it could be worth it.
This does not appear possible with grep or GNU grep. However it is possible with standard POSIX tools and a good shell like bash as leverage to obtain the desired output.
Note: neither python nor perl should be necessary for the solution. Worst case, use awk or sed.
One solution I rapidly prototyped is something like this (it does involve overhead of re-reading the file, and this solution depends on whether this overhead is OK, and the give-away is the original question's use of -1 as fixed number of lines of context which allows simple use of head & tail) :
$ OIFS="$IFS"; lines=`grep -n match greptext.txt | /bin/cut -f1 -d:`;
for l in $lines;
do IFS=""; match=`/bin/tail -n +$(($l-1)) greptext.txt | /bin/head -3`;
echo $match; echo "---";
done; IFS="$OIFS"
This might have some corner case associated with it, and this resets IFS when perhaps not necessary, though it is a hint for trying to use the power of POSIX shell & tools rather than a high level interpreter to get the desired output.
Opinion: All good operating systems have: grep, awk, sed, tr, cut, head, tail, more, less, vi as built-ins. On the best operating systems, these are in /bin.
I have some .rst files and I convert them to .tex file using standard sphinx converter.
In some .rst I have tables with special width like:
.. list-table::
:widths: 50 50
The resulting .tex always contains tables like:
\begin{tabulary}{\textwidth}{|L|L|}
So, the column width is lost.
How can I preserve column width when converting rst to latex?
I used comma separator too,
.. list-table::
:widths: 50 , 50
:header-rows: 1
* - SETTING
- DESCRIPTION
* - Enable
- Enables or disables internal tracing.
* - Verbose
- Enables or disables extended internal tracing.
but it doesn't work.. maybe I used a bad converter? What converter do you recommend?
actually the command
.. tabularcolumns:: |p{4.5cm}|p{8.5cm}|
is needed just before .. list-table::
https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-tabularcolumns
try:
:widths: 50, 50
with a comma separator.
The output also depends on how your table is written in rst.
I assumed that you were using the standard rst table syntax, not making tables from bulleted lists (as is possible). For more help, try http://docutils.sourceforge.net/docs/ref/rst/directives.html#tables
Also, if the 50, 50 is the column width, your latex code should look like this:
\begin{tabulary}{ 1\textwidth}{ | p{0.5} | p{0.5} | }
and:
\begin{tabulary}{total width of table}{| column width| column width|}
The docutils rst2latex writer has some issues with tables: http://docutils.sourceforge.net/docs/dev/todo.html#tables , so maybe your problem is related to that? I think the Sphinx writer is based on rst2latex and might thus have the same issues.
I can confirm that this:
.. list-table::
:widths: 10 40 50
* - Module
- Link
- Description
Works with rst2latex
\setlength{\DUtablewidth}{\linewidth}
\begin{longtable*}[c]{|p{0.104\DUtablewidth}|p{0.375\DUtablewidth}|p{0.465\DUtablewidth}|}
\hline
Module
&
Link
&
Description
\\
\hline
But with sphinx, I get what the OP put. So not an rst2latex issue I would gather.
The "Auto" width stuff the docs talk about is also not very functional for me, links tend to bleed over.
Since I have a huge documentation, I tried to fix the latex generation. Also, I consider Latex notation in rst files a disadvantage, because it's inconsistent and requires editors to partly learn a touchy markup language.
I replaced LaTeXTranslator.depart_table with my own version. I copied the original depart_table and added this code (shortened):
def my_depart_table (self, node):
totalColwidth = 0
givenColwidth = []
hasColwidth = False
for tgroup in node:
for tableColspec in tgroup:
try:
if tableColspec.has_key('colwidth'):
totalColwidth += tableColspec['colwidth']
givenColwidth.append(tableColspec['colwidth'])
hasColwidth = True
except:
print "colspec missing. \n"
# original code
if hasColwidth:
colspec = ""
for thisColwidth in givenColwidth:
colspec += ('>{\RaggedRight}p{%.3f\\linewidth}' % (0.95 * thisColwidth / totalColwidth))
#print "using widths: %.3f %s %s" % ((0.95 * thisColwidth / totalColwidth), thisColwidth, totalColwidth)
self.body.append('{' + colspec + '}\n')
# more original code
LaTeXTranslator.depart_table = my_depart_table
Im neither fluent in Python nor Sphinx, so use at own risk. I hope you get the idea or can even give advice.
If you use Python < 3.0 and want to remove the factor 0.95 completely, remember to either cast one of the integers to float or import division from __ future __.