Trying to translate BASIC code written in the 1990's to Python. I keep coming across two symbols, ! (exclamation mark) and . (period). I can't find any documentation online on what they do.
I have the code running but some of the outputs are not as expected - I am wondering if these might be the issue as I previously thought that the period may just be a typo for a multiplication.
Examples:
|
v
QWLOST = (((TW-TDAO)/(TWRT-TDAOR))^1.25)*((VISR/VIS)^0.25).(PW+PE)*DT
TFAVE = (TTO+TBO)/2!
^
|
In case anyone else in the future needs to know this.
! - defines a single
. - Was just a typo for * (multiplication)
I tried a few things in bwBasic (in Linux, in case that's relevant!).
bwBASIC: list
10: for i = 1 to 20
20: print i, ., . - i
30: next i
40: print ".="; .
This gave me:
bwBASIC: run
1 20 19
2 20 18
3 20 17
4 20 16
5 20 15
6 20 14
7 20 13
8 20 12
9 20 11
10 20 10
11 20 9
12 20 8
13 20 7
14 20 6
15 20 5
16 20 4
17 20 3
18 20 2
19 20 1
20 20 0
.= 20
Which would suggest that . (in bwBasic in any case) is the max number in a for loop.
Currently for a task, I am working with input files which give Matrix related test cases (Matrix Multiplication) i.e., example of an input file ->
N M
1 3 5 ... 6 (M columns)
....
5 4 2 ... 1 (N rows)
I was using simple read() to access them till now, but this is not efficient for large files of size > 10^2.
So I wanted to know is there some way to use processes to do this in parallel.
Also I was thinking of using multiple IO readers based on line, so then each process could read different segments of the file but couldn't find any helpful resources.
Thank you.
PS: Current code is using this:
io:fread(IoDev, "", "~d")
Did you consider to use re module? I did not make a performance test, but it may be efficient. In the following example I do not use the first "M N" line. So I did not put it in the matrix.txt file.
matrix file:
1 2 3 4 5 6 7 8 9
11 12 13 14 15 16 17 18 19
21 22 23 24 25 26 27 28 29
31 32 33 34 35 36 37 38 39
I made the conversion in the shell
1> {ok,B} = file:read_file("matrix.txt"). % read the complete file and store it in a binary
{ok,<<"1 2 3 4 5 6 7 8 9\r\n11 12 13 14 15 16 17 18 19\r\n21 22 23 24 25 26 27 28 29\r\n31 32 33 34 35 36 37 38 39">>}
2> {ok,ML} = re:compile("[\r\n]+"). % to split the complete binary in a list a binary, one for each line
{ok,{re_pattern,0,0,0,
<<69,82,67,80,105,0,0,0,0,0,0,0,1,8,0,0,255,255,255,255,
255,255,...>>}}
3> {ok,MN} = re:compile("[ ]+"). % to split the line into binaries one for each integer
{ok,{re_pattern,0,0,0,
<<69,82,67,80,73,0,0,0,0,0,0,0,17,0,0,0,255,255,255,255,
255,255,...>>}}
4> % a function to split a line and convert each chunk into integer
4> F = fun(Line) -> Nums = re:split(Line,MN), [binary_to_integer(N) || N <- Nums] end.
#Fun<erl_eval.7.126501267>
5> Lines = re:split(B,ML). % split the file into lines
[<<"1 2 3 4 5 6 7 8 9">>,<<"11 12 13 14 15 16 17 18 19">>,
<<"21 22 23 24 25 26 27 28 29">>,
<<"31 32 33 34 35 36 37 38 39">>]
6> lists:map(F,Lines). % map the function to each lines
[[1,2,3,4,5,6,7,8,9],
[11,12,13,14,15,16,17,18,19],
[21,22,23,24,25,26,27,28,29],
[31,32,33,34,35,36,37,38,39]]
7>
if you want to check the matrix size, you can replace the last line with:
[[NbRows,NbCols]|Matrix] = lists:map(F,Lines),
case (length(Matrix) == NbRows) andalso
lists:foldl(fun(X,Acc) -> Acc andalso (length(X) == NbCols) end,true,Matrix) of
true -> {ok,Matrix};
_ -> {error_size,Matrix}
end.
is there some way to use processes to do this in parallel.
Of course.
Also I was thinking of using multiple IO readers based on line, so
then each process could read different segments of the file but
couldn't find any helpful resources.
You don't seek to positions in a file by line, rather you seek to byte positions. While a file may look like a bunch of lines, a file is actually just one long sequence of characters. Therefore, you will need to figure out what byte positions you want to seek to in the file.
Check out file:position, file:pread.
I've already checked a similarly existing topic (How to read numeric data from a string in FORTRAN), but I'm not being able to do what I want.
I need to open a file and read a numeric value from a string. Bellow there's a section of the file in question. I want to read the integer next to 'ELEMENTS:', but so far I'm not being able to do so.
ELEMENT GROUP 2.4.6
GROUP: 1 ELEMENTS: 187169 MATERIAL: 2 NFLAGS: 1
fluid
0
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
Can someone please help me here?
Ok guys, thanks to your answers the program is working!
For further reference, here's the reading part of the code:
READ(77,'(A)') str
ipos = INDEX(str,"ELEMENTS:",back=.true.) + 9
READ (str(1+ipos:),*) k
PRINT*, k
Thank for the answers.
Data Encryption Standard (DES) algorithm : (Using sbox 2) to show that Two output bits from each S-box affect middle bits of the next round and the other two affect the end bits.
The permutation table P is defined in the following table.
16 7 20 21 29 12 28 17 [END BITS]
1 15 23 26 5 18 31 10 [MIDDLE BITS]
2 8 24 14 32 27 3 9 [MIDDLE BITS]
19 13 30 6 22 11 4 25 [END BITS]
From the table above you can see that bits 7 and 6 refer to the end bits and 5 and 8 refer to the middle bits.
However am not sure if this is correct because if we consider E table the 5,6 are end bits and 7,8 affecting middle bit. What is correct ?
Don't fully understand the question but your first statement about bits 7,6,5 and 8 is true, but remember that the "cascade effect" will make all the changes made by the P-table will go to the "right side" of the equation; but at the same time these will interact in the next round in the left side!
To fully understand the process check out this link: http://www.cronos.est.pr/DES.php
Since length is a generic method, why can't I do
length.character <- nchar
? It seems that strings are treated special in R. Is there a reason for that? Would you discourage defining functions like head.character and tail.character?
If you look at the help page for InternalMethods (mentioned in the details portion of the help page for length) it states that
For efficiency, internal dispatch only
occurs on objects, that
is those for which ‘is.object’ returns true.
Vectors are not objects in the same sense as other objects are, so the method dispatch is not being done on any basic vectors (not just character). if you really want to use this type of dispatch you need a defined object, e.g.:
> tmp <- state.name
> class(tmp) <- 'mynewclass'
> length.mynewclass <- nchar
> length(tmp)
[1] 7 6 7 8 10 8 11 8 7 7 6 5 8 7 4 6 8 9 5 8 13 8 9 11 8
[26] 7 8 6 13 10 10 8 14 12 4 8 6 12 12 14 12 9 5 4 7 8 10 13 9 7
>
My 2c:
Strings are not treated specially in R. If length did the same thing as nchar, then you would get unexpected results if you tried to compute length(c("foo", "bazz")). Or to put it another way, would you expect the length of a numeric vector to return the number of digits in each element of the vector or the length of the vector itself?
Also creating this method might side-effect other functions which expect the normal string behavior.
Now I found a reason not to define head.character: it changes the way how head works. For example:
head.character <- function(s,n) if(n<0) substr(s,1,nchar(s)+n) else substr(s,1,n)
test <- c("abc", "bcd", "cde")
head("abc", 2) # works fine
head(test,2)
Without the definition of head, the last line would return c("abc", "bcd"). Now, with head.character defined, this function is applied to each element of the list and returns c("ab", "bc", "cd").
But I have a strhead and a strtail function now.. :-)