I am trying to understand a small read function in my program I am trying to decipher.The code is below
READ (LREST, END=350, ERR=350) ICHR
IF (ICHR .EQ. ICKLNK) THEN
DO L = 1, 4
READ (LREST, END=350, ERR=350)
ENDDO
So basically LREST is some kind of an argument provided for this subroutine this function is in. However, I found that LREST is not defined anywhere(used grep to see where LREST is defined in my *.f files. So my questions is what is that LREST doing there in READ function. I thought the location LREST is at is where the unit is defined.
Second questions is that ICHR is a 16 character string variable define for this subroutine. However, the contents of ICHR have not been assigned. I have no idea what this READ function is trying to read from.
Going over to IF statement, ICKLNK is another 16 character string variable with a defined strings. Because ICHR is not defined, does that mean this if statement never gets entered in?
Finally, the do loop( or for loop) has variable L in it but it is not even being used for read function inside of the loop.
Im a beginning in fortran so I may just be lacking a very basic knowledge but if you know an answer to my question please let me know. Thanks!
Han
You are correct that LREST is specifying the unit number (or internal file if it is character). You seem to suggest that LREST is an argument in this subroutine or function, which means its value is passed in by whoever calls the function. Showing us only a small piece of the code makes it hard to provide further details.
Again, you say ICHR is an argument to the procedure, so it takes on the value of whatever was passed in by the call. ICLNK is probably similar, but you didn't show all the code.
The DO (not for) loop is using L just as a counter; it doesn't need to be referenced inside the loop.
Related
I have functions process and matrix. The following code works
process(matrix({{2,4,6},{8,10,12},{14,16,20}}))
However the following doesn't work.
n='matrix({{2,4,6},{8,10,12},{14,16,20}})'
process(n)
It throws some error. The reason is obvious that process takes n as string rather than the output of the function matrix. So the basic difficulty involved here is about evaluating string from variable n and then give it as argument to the function process. Here loadstring function is of no use as matrix is local function and can't be referred from loadstring.
Is there any work around for this? I hope that I have clearly stated the problem here. It is about evaluating (or unloading) string and then passing it as argument to another function. Any help will be appreciated. Thanks.
as matrix is local function
Lua takes local declarations seriously. If a variable is declared local, it can only be accessed by code which is statically within the local scope of that variable. Strings which you later turn into code are not statically in the local scope and therefore cannot access local variables.
Now, with Lua 5.2+, you can provide load with a second parameter, a table which represents the global environment against which that Lua chunk will be built. If that table contains a matrix value, then the loaded string can access it. For Lua 5.1, you'd have to use setfenv on the function returned to load to accomplish a similar effect. The Lua 5.2+ method would look like this:
local env = {matrix = matrix}
local func = load("return matrix({{2,4,6},{8,10,12},{14,16,20}})", nil, "t", env)
process(func())
Note the following:
You must create an explicit table which is the global environment. There's nothing you can pass that says "make my locals available"; you have to put every local you'd like to access there. Which is, generally speaking, why you pass these things as parameters or just make them globals.
You explicitly need the "return " there if you want to get the results of the call to matrix.
You have to call the function. Functions are values in Lua, so you can freely pass them around. But if you want to pass the results of a function to another function, you have to actually call it.
Lets say that there is a function in my Delphi app:
MsgBox
and there is a string which has MsgBox in it.
I know what most of you are going to say is that its possible, but I think it is possible because I opened the compiled exe(compiled using delphi XE2) using a Resource Editor, and that resource editor was built for Delphi. In that, I could see most of the code I wrote, as I wrote it. So since the variables names, function names etc aren't changed during compile, there should a way to execute the functions from a string, but how? Any help will be appreciated.
EDIT:
What I want to do is to create a simple interpreter/scripting engine. And this is how its supposed to work:
There are two files, scr.txt and arg.txt
scr.txt contains:
msg_show
0
arg.txt contains:
"Message"
And now let me explain what that 0 is:
First, scr.txt's first line is function name
second line tells that at which line its arguments are in the arg.txt, i.e 0 tells that "Message" is the argument for msg_show.
I hope my question is now clear.
I want to make a simple scripting engine.
In order to execute arbitrary code stored as text, you need a compiler or an interpreter. Either you need to write one yourself, or embed one that already exists. Realistically, the latter option is your best option. There are a number available but in my view it's hard to look past dwscript.
I think I've already solved my problem! The answer is in this question's first answer.
EDIT:
But with that, as for a workaround of the problem mentioned in first comment, I have a very easy solution.
You don't need to pass all the arguments/parameters to it. Just take my example:
You have two files, as mentioned in the question. Now you need to execute the files. It is as simple as that:
read the first line of scr.txt
check if it's a function. If not, skip the line
If yes, read the next line which tells the index where it's arguments are in arg.txt
pass on the index(an integer) to the "Call" function.
Now to the function which has to be executed, it should know how many arguments it needs. i.e 2
Lets say that the function is "Sum(a,b : integer)".It needs 2 arguments
Now let the function read the two arguments from arg.txt.
And its done!
I hope it will help you all.
And I can get some rep :)
I have to write a MATLAB function with the following description:
function counts = letterStatistics(filename, allowedChar, N)
This function is supposed to open a text file specified by filename and read its entire contents. The contents will be parsed such that any character that isn’t in allowedChar is removed. Finally it will return a count of all N-symbol combinations in the parsed text. This function should be stored in a file name “letterStatistics.m” and I made a list of some commands and things of how the function should be organized according to my professors' lecture notes:
Begin the function by setting the default value of N to 1 in case:
a. The user specifies a 0 or negative value of N.
b. The user doesn’t pass the argument N into the function, i.e., counts = letterStatistics(filename, allowedChar)
Using the fopen function, open the file filename for reading in text mode.
Using the function fscanf, read in all the contents of the opened file into a string variable.
I know there exists a MATLAB function to turn all letters in a string to lower case. Since my analysis will disregard case, I have to use this function on the string of text.
Parse this string variable as follows (use logical indexing or regular expressions – do not use for loops):
a. We want to remove all newline characters without this occurring:
e.g.
In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.
In my younger and more vulnerableyears my father gave me some advicethat I’ve been turning over in my mindever since.
Replace all newline characters (special character \n) with a single space: ' '.
b. We will treat hyphenated words as two separate words, hence do the same for hyphens '-'.
c. Remove any character that is not in allowedChar. Hint: use regexprep with an empty string '' as an argument for replace.
d. Any sequence of two or more blank spaces should be replaced by a single blank space.
Use the provided permsRep function, to create a matrix of all possible N-symbol combinations of the symbols in allowedChar.
Using the strfind function, count all the N-symbol combinations in the parsed text into an array counts. Do not loop through each character in your parsed text as you would in a C program.
Close the opened file using fclose.
HERE IS MY QUESTION: so as you can see i have made this list of what the function is, what it should do, and using which commands (fclose etc.). the trouble is that I'm aware that closing the file involves use of 'fclose' but other than that I'm not sure how to execute #8. Same goes for the whole function creation. I have a vague idea of how to create a function using what commands but I'm unable to produce the actual code.. how should I begin? Any guidance/hints would seriously be appreciated because I'm having programmers' block and am unable to start!
I think that you are new to matlab, so the documentation may be complicated. The root of the problem is the basic understanding of file I/O (input/output) I guess. So the thing is that when you open the file using fopen, matlab returns a pointer to that file, which is generally called a file ID. When you call fclose you want matlab to understand that you want to close that file. So what you have to do is to use fclose with the correct file ID.
fid = open('test.txt');
fprintf(fid,'This is a test.\n');
fclose(fid);
fid = 0; % Optional, this will make it clear that the file is not open,
% but it is not necessary since matlab will send a not open message anyway
Regarding the function creation the syntax is something like this:
function out = myFcn(x,y)
z = x*y;
fprintf('z=%.0f\n',z); % Print value of z in the command window
out = z>0;
This is a function that checks if two numbers are positive and returns true they are. If not it returns false. This may not be the best way to do this test, but it works as example I guess.
Please comment if this is not what you want to know.
this is my first time asking a question so let me know if I am doing something wrong (post wise)
I am trying to create a function that writes into a .txt but i seem to get two very different results between calling it from within a module, and writing the same loop in the shell directly. The code is as follows:
def function(para1, para2): #para1 is a string that i am searching for within para2. para2 is a list of strings
with open("str" + para1 +".txt", 'a'. encoding = 'utf-8') as file:
#opens a file with certain naming convention
n = 0
for word in para2:
if word == para1:
file.write(para2[n-1]+'\n')
print(para2[n-1]) #intentionally included as part of debugging
n+=1
function("targetstr". targettext)
#target str is the phrase I am looking for, targettext is the tokenized text I am
#looking through. this is in the form of a list of strings, that is the output of
#another function, and has already been 'declared' as a variable
when I define this function in the shell, I get the correct words appearing. However, when i call this same function through a module(in the shell), nothing appears in the shell, and the text file shows a bunch of numbers (eg: 's93161), and no new lines.
I have even gone to the extent of including a print statement right after declaration of the function in the module, and commented everything but the print statement, and yet nothing appears in the shell when I call it. However, the numbers still appear in the text file.
I am guessing that there is a problem with how I have defined the parameters or how i cam inputting the parameters when I call the function.
As a reference, here is the desired output:
‘She
Ashley
there
Kitty
Coates
‘Let
let
that
PS: Sorry if this is not very clear as I have very limited knowledge on speaking python
I have found the solution to issue. Turns out that I need to close the shell and restart everything before the compiler recognizes the changes made to the function in the module. Thanks to those who took a look at the issue, and those who tried to help.
Can someone explain call by name, reference, and value in depth and also compare them to each other?
Simple examples would be great as well. I am really focused on call by name, it feels like it's very similar to call by reference.
call by name : in call by name actual argument is not evaluated at the place of function calling rather they replace all the instance of corresponding formal parameters in text.
Actual argument are evaluated as many times as required.
Actual argument are evaluated within "caller" environment (if needed) :