I have a c(java,c++) file with t functions in it. Is there any way, I can find out the function with smallest no. of words.
Given a function, I can calculate the no.of words in it using yylex().
Since you haven't specified the language for implementation of the solution, I will propose a description of the algorith I would use.
You can iterate through the file and use regex to detect function prototipes (such as "^(\w+( )?){2,}\([^!##$+%^]+?\)" for C functions). Once you've detected you have a function, you iterate through the next lines and count the words. Once you detect a line containing another function definition, you will store the function with its word count and get to the next until you reach the end of the file.
If we consider you need only the function with the least number of words, you can just store the function name only if it has fewer words than the previous one.
Related
Let X be a square matrix. We want to force it to be Hermitian, that is: self-conjugate-transpose. X = X^H = conj(X^T). To do this in Python with numpy is easy:
X = 0.5*(X + np.conj(X.T))
I haven't found in NumPy a single function that does it in a single experssion f(x).
The question is should I define a new function to do it? E.g.
def make_hermitian(X):
return 0.5*(X + np.conj(X.T))
(one can come up with short name, e.g. "make_h" or "herm" or "selfconj").
Pros: more readable code, one operation in shorter form. If one uses shorter name it saves writing when repeated many times, and makes modification in this operation far more easy and comfortable (need to change only in place).
Cons: replaces a very short and straight-forward expression which is self-evident.
What is more appropriate way of programming: define a new function or just write the explicit expression repeatedly?
I would say it depends on how many times you need to reuse that function.
If it's more than twice, then definitely make a function. If it's only once or twice, I would say it's up to you. If you choose to go with no function, add a short comment specifying what such piece of code is supposed to do.
My preference in any case would be defining a function with a meaningful name, because if anyone else is going to / supposed to read the code, they may not know or remember how to achieve a Hermitian matrix, and hence the math alone ain't going to be sufficient.
On the other hand, a meaningful function name will tell them clearly what it's going on, and they can google after what a Hermitian matrix is.
I have a function where I want to solve for many variables separately, do I have to write down the function every time in terms of the other variable?
x,xG,xR
y = e.^tan(x.^2)+cos.^2(x);
yG = e.^tan(xG.^2)+cos.^2(xG);
First you cannot write an expression like cos.^2(x). If x is a single variable (ie x=pi) you could write either cos(x)^2 or cos(x^2). If x is a vector (a column vector might be x=[3;4;pi] and a row vector might be x=[3,4,pi], then you might write cos(x).^2 or cos(x.^2). The role of the period (.) in octave is explained here: https://octave.org/doc/v4.0.3/Arithmetic-Ops.html
Another issue has to do with understanding the difference between an expression: x=e^tanh(y); and a function. The later is a separate chunk of code that can be invoked from anywhere in your program.
Consider this simple example
1;
function y=myfunc(x)
y=exp(tanh(x));
endfunction
## main program
xxx=pi/3;
yyy=myfunc(xxx);
printf('%7.3f %7.3f\n',xxx,yyy)
y=exp(tanh(pi/3))
comments: The '1' in the first line tells Octave that there is more to the script than just the following function: the main program has to be interpreted as well. The function line specifies that inside the function, the input will be called x and the output y, so when my function is called from main, the input is xxx(=pi/2) and the output is yyy. The last line in this tiny script is an expression that does the same thing as the function. Note that since I didn't include a semi-colon at the end of that line the result is printed out
I suggest you play with this for a while, then if you have more questions, ask them in a new question.
I have a file with 13 columns and 41 lines consisting of the coefficients for the Joback Method for 41 different groups. Some of the values are non-existing, though, and the table lists them as "X". I saved the table as a .csv and in my code read the file to an array. An excerpt of two lines from the .csv (the second one contains non-exisiting coefficients) looks like this:
48.84,11.74,0.0169,0.0074,9.0,123.34,163.16,453.0,1124.0,-31.1,0.227,-0.00032,0.000000146
X,74.6,0.0255,-0.0099,X,23.61,X,797.0,X,X,X,X,X
What I've tried doing was to read and define an array to hold each IOSTAT value so I can know if an "X" was read (that is, IOSTAT would be positive):
DO I = 1, 41
(READ(25,*,IOSTAT=ReadStatus(I,J)) JobackCoeff, J = 1, 13)
END DO
The problem, I've found, is that if the first value of the line to be read is "X", producing a positive value of ReadStatus, then the rest of the values of those line are not read correctly.
My intent was to use the ReadStatus array to produce an error message if JobackCoeff(I,J) caused a read error, therefore pinpointing the "X"s.
Can I force the program to keep reading a line after there is a reading error? Or is there a better way of doing this?
As soon as an error occurs during the input execution then processing of the input list terminates. Further, all variables specified in the input list become undefined. The short answer to your first question is: no, there is no way to keep reading a line after a reading error.
We come, then, to the usual answer when more complicated input processing is required: read the line into a character variable and process that. I won't write complete code for you (mostly because it isn't clear exactly what is required), but when you have a character variable you may find the index intrinsic useful. With this you can locate Xs (with repeated calls on substrings to find all of them on a line).
Alternatively, if you provide an explicit format (rather than relying on list-directed (fmt=*) input) you may be able to do something with non-advancing input (advance='no' in the read statement). However, as soon as an error condition comes about then the position of the file becomes indeterminate: you'll also have to handle this. It's probably much simpler to process the line-as-a-character-variable.
An outline of the concept (without declarations, robustness) is given below.
read(iunit, '(A)') line
idx = 1
do i=1, 13
read(line(idx:), *, iostat=iostat) x(i)
if (iostat.gt.0) then
print '("Column ",I0," has an X")', i
x(i) = -HUGE(0.) ! Recall x(i) was left undefined
end if
idx = idx + INDEX(line(idx:), ',')
end do
An alternative, long used by many many Fortran programmers, and programmers in other languages, would be to use an editor of some sort (I like sed) and modify the file by changing all the Xs to NANs. Your compiler has to provide support for IEEE NaNs for this to work (most of the current crop in widespread use do) and they will correctly interpret NAN in the input file to a real number with value NaN.
This approach has the benefit, compared with the already accepted (and perfectly good) answer, of not requiring clever programming in Fortran to parse input lines containing mixed entries. Use an editor for string processing, use Fortran for reading numbers.
So I've been Googling function arguments and I would like to understand arguments better.
I am new to as3, to summarize arguments with my current knowledge, I would say they are like temporary variables? I don't fully get why you add parameters which are names that can be any value? Then you like call these parameters later and their order magically replace these parameters, but why? I'm missing some understanding here to fully grasp their use. Why make parameters in a function and then add the values later? If I'm even saying that right.
function name( applepie, sugar, healthyfood)
name( 1,2,3)
What was the point?
Also I haven't found a syntax book that describes what every symbol does yet that I can just search like () and it describes it, I heard some just use Google, but the results I got weren't very fruitful. Hence why I'm here asking. Personally I don't want to continue on until I fully grasps the use of (). I also tried Adobe website search but that didn't work out well either, was a good amount of searches trust me....
A function is a piece of code that can be reused many times in different contexts. You pass arguments to a function to tell the function something about the context in which it is being called; as a trivial example, when you call the print() function you must specify what you want the function to print. In your example name(applepie, sugar, healthyfood) the function should use the value supplied in place of each argument somewhere in its body, because the function doesn't know what values it will be passed, in the body of the function definition you use the names you chose (which should be descriptive) to refer to the values which will be passed in later and which will presumably be different each time it is called.
The parentheses are used for delimiting different semantic elements, in this case they are telling the interpreter where the argument list starts and stops.
First, here the way i'm calling the function :
eval([functionName '(''stringArg'')']); % functionName = 'someStringForTheFunctionName'
Now, I have two functionName functions in my path, one that take the stringArg and another one that takes something else. I'm getting some errors because right now the first one it finds is the function that doesn't take the stringArg. Considering the way i'm calling the functionName function, how is it possible to call the correct function?
Edit:
I tried the function which :
which -all someStringForTheFunctionName
The result :
C:\........\x\someStringForTheFunctionName
C:\........\y\someStringForTheFunctionName % Shadowed
The shadowed function is the one i want to call.
Function names must be unique in MATLAB. If they are not, so there are duplicate names, then MATLAB uses the first one it finds on your search path.
Having said that, there are a few options open to you.
Option 1. Use # directories, putting each version in a separate directory. Essentially you are using the ability of MATLAB to apply a function to specific classes. So, you might set up a pair of directories:
#char
#double
Put your copies of myfun.m in the respective directories. Now when MATLAB sees a double input to myfun, it will direct the call to the double version. When MATLAB gets char input, it goes to the char version.
BE CAREFUL. Do not put these # directories explicitly on your search path. DO put them INSIDE a directory that is on your search path.
A problem with this scheme is if you call the function with a SINGLE precision input, MATLAB will probably have a fit, so you would need separate versions for single, uint8, int8, int32, etc. You cannot just have one version for all numeric types.
Option 2. Have only one version of the function, that tests the first argument to see if it is numeric or char, then branches to perform either task as appropriate. Both pieces of code will most simply be in one file then. The simple scheme will have subfunctions or nested functions to do the work.
Option 3. Name the functions differently. Hey, its not the end of the world.
Option 4: As Shaun points out, one can simply change the current directory. MATLAB always looks first in your current directory, so it will find the function in that directory as needed. One problem is this is time consuming. Any time you touch a directory, things slow down, because there is now disk input needed.
The worst part of changing directories is in how you use MATLAB. It is (IMHO) a poor programming style to force the user to always be in a specific directory based on what code inputs they wish to run. Better is a data driven scheme. If you will be reading in or writing out data, then be in THAT directory. Use the MATLAB search path to categorize all of your functions, as functions tend not to change much. This is a far cleaner way to work than requiring the user to migrate to specific directories based on how they will be calling a given function.
Personally, I'd tend to suggest option 2 as the best. It is clean. It has only ONE main function that you need to work with. If you want to keep the functions district, put them as separate nested or sub functions inside the main function body. Inside of course, they will have distinct names, based on how they are driven.
OK, so a messy answer, but it should do it. My test function was 'echo'
funcstr='echo'; % string representation of function
Fs=which('-all',funcstr);
for v=1:length(Fs)
if (strcmp(Fs{v}(end-1:end),'.m')) % Don''t move built-ins, they will be shadowed anyway
movefile(Fs{v},[Fs{v} '_BK']);
end
end
for v=1:length(Fs)
if (strcmp(Fs{v}(end-1:end),'.m'))
movefile([Fs{v} '_BK'],Fs{v});
end
try
eval([funcstr '(''stringArg'')']);
break;
catch
if (strcmp(Fs{v}(end-1:end),'.m'))
movefile(Fs{v},[Fs{v} '_BK']);
end
end
end
for w=1:v
if (strcmp(Fs{v}(end-1:end),'.m'))
movefile([Fs{v} '_BK'],Fs{v});
end
end
You can also create a function handle for the shadowed function. The problem is that the first function is higher on the matlab path, but you can circumvent that by (temporarily) changing the current directory.
Although it is not nice imo to change that current directory (actually I'd rather never change it while executing code), it will solve the problem quite easily; especially if you use it in the configuration part of your function with a persistent function handle:
function outputpars = myMainExecFunction(inputpars)
% configuration
persistent shadowfun;
if isempty(shadowfun)
funpath1 = 'C:\........\x\fun';
funpath2 = 'C:\........\y\fun'; % Shadowed
curcd = cd;
cd(funpath2);
shadowfun = #fun;
cd(curcd); % and go back to the original cd
end
outputpars{1} = shadowfun(inputpars); % will use the shadowed function
oupputpars{2} = fun(inputparts); % will use the function highest on the matlab path
end
This problem was also discussed here as a possible solution to this problem.
I believe it actually is the only way to overload a builtin function outside the source directory of the overloading function (eg. you want to run your own sum.m in a directory other than where your sum.m is located.)
EDIT: Old answer no longer good
The run command won't work because its a function, not a script.
Instead, your best approach would be honestly just figure out which of the functions need to be run, get the current dir, change it to the one your function is in, run it, and then change back to your start dir.
This approach, while not perfect, seems MUCH easier to code, to read, and less prone to breaking. And it requires no changing of names or creating extra files or function handles.