I am trying to read a text file and store the data inside into structs and I am interested in finding out how to ignore the first 4 lines (text header) in the text file.
This is the text file:
text file
I am only going to need the numeric values from it (year int, month int, max double, etc.) and ignore the four text lines above them.
This is the code I use to store the values as a collection of structs:
code
You can use func dropFirst(_ n: Int) to skip initial lines:
let lines = contents.components(separatedBy: "\n")
for line in lines.dropFirst(4) {
// ...
}
dropFirst(4) returns an “array slice” with all but the first 4
elements in the lines array, which means that the element storage
is not duplicated.
If it's always 4 lines then #Martin R has a good answer, otherwise you could see if the first word can be converted to an int like
for line in filtered {
let x = line.components(separatedBy: " ")
guard let year = Int(x[0] else {
continue
}
....
so I am working on a graphical calculator (bit more of a challenge than the basic windows one), and I want to be able to do the entire "math" in one textfield, just like typing in "5+3-5*11/3" and it gives you the solution when you press '='
I decided to make it with arrays of numbers and symbols, but I have no idea how to make it to fill the next array if this one already is used:
var numbers:Array = new Array("","","","","","","","","","","","","","","","");
var actions:Array = new Array("","","","","","","","","","","","","","","","");
I am using split to split the numbers I input with symbols, and I want the numbers to be placed in the arrays. Example: I type in 555+666 and then I need to have something like
if (numbers[0] = "") {numbers[0] = 555}
else if (numbers[1] = "") {numbers[1] = 555}
else if.....
Know what I mean?
Pretty hard to describe...
something like... When I type in a number, if the numbers[0] is already filled, go fill in numbers[1], if numbers[1] is filled, go to numbers[2] etc
Even if I agree with #Nbooo and the Reverse Polish Notation
However Vectors may have a fixed length.
This is not an answer but just an example (if the length of Your Array must be defined):
//Just for information..
var numbs:Vector.<Number> = new Vector.<Number>(10,true);
var count:uint = 1;
for (var i in numbs){
numbs[i] = count++
}
trace(numbs);
// If You try to add an element to a Vector,
// You will get the following Error at compile time :
/*
RangeError: Error #1126: Cannot change the length of a fixed Vector.
at Vector$double/http://adobe.com/AS3/2006/builtin::push()
at Untitled_fla::MainTimeline/frame1()
*/
numbs.push(11);
// Will throw an Error #1126
trace(numbs);
If You use this code to update a fixed Vector, this will not throw an ERROR :
numbs[4]=11;
trace(numbs);
Output :
1,2,3,4,5,6,7,8,9,10
1,2,3,4,11,6,7,8,9,10
// length is 10, so no issue...
If You consider the performance between Arrays and vectors check this reference : Vector class versus Array class
I hope this may be helpful.
[EDIT]
I suggest you to check at those links too :
ActionScript 3 fundamentals: Arrays
ActionScript 3 fundamentals: Associative arrays, maps, and dictionaries
ActionScript 3 fundamentals: Vectors and ByteArrays
[/EDIT]
Best regards.
Nicolas.
What you want to implement is the Reverse Polish Notation. In actionscript3 arrays are dynamic, not fixed size, that means you can add elements to the array without concern about capacity (at least in your case).
const array:Array = new Array();
trace(array.length); // prints 0
array.push(1);
array.push(2);
trace(array.length); // prints 2
I suggest using "push" and "pop" methods of Array/Vector, since it's much more natural for such task. Using those methods will simplify your implementation, since you'll get rid of unnecessary checks like
if (numbers[1] == "") {...}
and replace it just with:
numbers.push(value);
and then to take a value from the top:
const value:String = numbers.pop();
What I want to achieve:
I have a function where I want to loop through all possible combinations of printable ascii-characters, starting with a single character, then two characters, then three etc.
The part that makes this difficult for me is that I want this to work for as many characters as I can (leave it overnight).
For the record: I know that abc really is 97 98 99, so a numeric representation is fine if that's easier.
This works for few characters:
I could create a list of all possible combinations for n characters, and just loop through it, but that would require a huge amount of memory already when n = 4. This approach is literally impossible for n > 5 (at least on a normal desktop computer).
In the script below, all I do is increment a counter for each combination. My real function does more advanced stuff.
If I had unlimited memory I could do (thanks to Luis Mendo):
counter = 0;
some_function = #(x) 1;
number_of_characters = 1;
max_time = 60;
max_number_of_characters = 8;
tic;
while toc < max_time && number_of_characters < max_number_of_characters
number_of_characters = number_of_characters + 1;
vectors = [repmat({' ':'~'}, 1, number_of_characters)];
n = numel(vectors);
combs = cell(1,n);
[combs{end:-1:1}] = ndgrid(vectors{end:-1:1});
combs = cat(n+1, combs{:});
combs = reshape(combs, [], n);
for ii = 1:size(combs, 1)
counter = counter + some_function(combs(ii, :));
end
end
Now, I want to loop through as many combinations as possible in a certain amount of time, 5 seconds, 10 seconds, 2 minutes, 30 minutes, so I'm hoping to create a function that's only limited by the available time, and uses only some reasonable amount of memory.
Attempts I've made (and failed at) for more characters:
I've considered pre-computing the combinations for two or three letters using one of the approaches above, and use a loop only for the last characters. This would not require much memory, since it's only one (relatively small) array, plus one or more additional characters that gets looped through.
I manage to scale this up to 4 characters, but beyond that I start getting into trouble.
I've tried to use an iterator that just counts upwards. Every time I hit any(mod(number_of_ascii .^ 1:n, iterator) == 0) I increment the m'th character by one. So, the last character just repeats the cycle !"# ... ~, and every time it hits tilde, the second character increments. Every time the second character hits tilde, the third character increments etc.
Do you have any suggestions for how I can solve this?
It looks like you're basically trying to count in base-26 (or base 52 if you need CAPS). Each number in that base will account for a specific string of character. For example,
0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,10,11,12,...
Here, cap A through P are just symbols that are used to represent number symbols for base-26 system. The above simply represent this string of characters.
a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,ba,bb,bc,...
Then, you can simply do this:
symbols = ['0','1','2','3','4','5','6','7','8','9','A','B','C','D','E',...
'F','G','H','I','J','K','L','M','N','O','P']
characters = ['a','b','c','d','e','f','g','h','i','j','k','l',...
'm','n','o','p','q','r','s','t','u','v','w','x','y','z']
count=0;
while(true)
str_base26 = dec2base(count,26)
actual_str = % char-by-char-lookup-of-str26 to chracter string
count=count+1;
end
Of course, it does not represent characters that begin with trailing 0's. But that should be pretty simple.
You were not far with your idea of just getting an iterator that just counts upward.
What you need with this idea is a map from the integers to ASCII characters. As StewieGriffin suggested, you'd just need to work in base 95 (94 characters plus whitespace).
Why whitespace : You need something that will be mapped to 0 and be equivalent to it. Whitespace is the perfect candidate. You'd then just skip the strings containing any whitespace. If you don't do that and start directly at !, you'll not be able to represent strings like !! or !ab.
First let's define a function that will map (1:1) integers to string :
function [outstring,toskip]=dec2ASCII(m)
out=[];
while m~=0
out=[mod(m,95) out];
m=(m-out(1))/95;
end
if any(out==0)
toskip=1;
else
toskip=0;
end
outstring=char(out+32);
end
And then in your main script :
counter=1;
some_function = #(x) 1;
max_time = 60;
max_number_of_characters = 8;
currString='';
tic;
while numel(currString)<=max_number_of_characters&&toc<max_time
[currString,toskip]=dec2ASCII(counter);
if ~toskip
some_function(currString);
end
counter=counter+1;
end
Some random outputs of the dec2ASCII function :
dec2ASCII(47)
ans =
O
dec2ASCII(145273)
ans =
0)2
In terms of performance I can't really elaborate as I don't know what you want to do with your some_function. The only thing I can say is that the running time of dec2ASCII is around 2*10^(-5) s
Side note : iterating like this will be very limited in terms of speed. With the function some_function doing nothing, you'd just be able to cycle through 4 characters in around 40 minutes, and 5 characters would already take up to 64 hours. Maybe you'd want to reduce the amount of stuff you want to pass through the function you iterate on.
This code, though, is easily parallelizable, so if you want to check more combinations, I'd suggest trying to do it in a parallel manner.
I have to allocate a dynamic array and i know how many columns there will be on the array but i don't know how many rows, all i have is a number on a .txt file. I have tried the following code but i am not sure it will work:
int x = (int)fgetc(file)-48;
Since the ascii value of 0 is 48, i assumned that i needed to cast the character read from the file in order to be able to use it as my rows number.
I assume i should be able to allocate the array the 2D array as it follows:
m = (int **)malloc(x*sizeof(int*));
for (i=0;i<x;i++)
{
m[i] = (int*)malloc(10*sizeof(int));
}
Am i correct? Any help will be highly apretiated.
You can design a list and dynamically insert your rows.
First off fgetc() returns an integer, so casting it as an int will do nothing. Second you're only reading in one integer at a time with fgetc() so you will have a 1 digit number in x.
Your array allocation looks correct, but you can also allocate the columns as an array of int * on the stack and then allocate the rows dynamically as m[i] = (int*)malloc(x*sizeof(int)); from i = 0->9
Do I understand correctly that your file looks like
327 // number of lines
1 2 3 // line 1
33 44 55 // line 2
... repeats until 327 lines have been printed, all with 3 elements? Note that the line breaks would be optional and could be any whitespace.
The canonical way to read a number from text in C is using scanf. scanf uses, like printf, a weird looking format string as the fist parameter. Each basic type has a letter associated with it, for integers it's d or, more intuitively, i. These letters are prefixed with a %. So to read an integer, you would write scanf("%d", &lines); if lines is an int holding the number of lines. (Do rather not use x, for readability).
The way you allocate your array is correct (provided x holds the number of lines and 10 is the known line length). One style issue is that the 10 should be #defined as a macro so that you can use e.g. malloc(LINE_LEN*sizeof(int)). That helps later when that number should ever change and you have (in a real world program) scattered references to m over several source files.
If this is just a little program and the array isnt't inordinately large and does not need to live longer than the function call (which, in the case of main(), may be long enough in any case), the easiest would be to use a variable size array in C; provided you use a modestly modern compiler:
#define LINE_LEN 10
int lineCount;
scanf("%d", &lineCount);
int m[lineCount][LINE_LEN];
// fill from file
If you compile with gcc you'll probably need to specify "-std=c99" as a command line option for that.
I want to store user inputs in an array, but when a person enters a new number, the previous input gets replaced. How can I create such an array in Matlab such that I can store all inputs without replacement? I am a beginner so bear with me
Thanks
You simply need to copy the contents of the input buffer into a data struct that won't be overwritten.
Cell arrays are good for that (see the userInputs variable below) . Without better knowledge of your code, I'm guessing the user input is stored in a variable named buffer. Here's how I would do it:
% a new buffer comes in
userInputs{iInput} = buffer;
iInput = iInput + 1;
% keep looking for more inputs
Good luck!
If you want a numeric matrix here is an example:
n = 2; %# number of rows
m = 3; %# number of columns
out = zeros(n,m); %# the output
k = 1; %# counter
while k <= n*m
x = input('Enter a number or Enter to stop: ');
if isempty(x)
break
else
out(k)=x;
end
k=k+1;
end
disp(xx)