I have some code
::redo::
io.write("input: ")
var = io.read("*n")
if var then
if var > 5 and var < 10 then io.write("yes\n") goto redo
else io.write("invalid\n") goto redo end
else io.write("invalid\n") goto redo end
that is supposed to check a numeric input value and return if it's within a certain range. If it isn't a numeric value, it's supposed to "redo" the script and ask for input again. The issue is that whenever it takes an input that isn't a number it repeats io.write("input: ") and io.write("invalid\n") unceasingly meaning it's skipping the var = io.read("*n") line. Is there a special meaning or quirk to io.read("*n") that keeps it from reevaluating? The code seems to work if replaced with io.read()
When you call io.read('*n') and it doesn't find a number, it doesn't use up the input, and any calls to io.read('*n') will read the same input over and over. You need to eat up the input and discard it by calling io.read('*l'). That will let you read new input with io.read('*n').
Another method would be to read a line with io.read('*l'), extract a number from it with string.match and convert it to a number with tonumber. Then you don't have to read the same input twice, but you'd have to decide what types of number notation you want to match. (io.read('*n') accepts various types of numbers, including hexadecimal and scientific notation.)
Related
The following code always outputs "not":
print "input a number please. "
TestNumber = gets
if TestNumber % 2 == 0
print "The number is even"
else
print "The number is not even"
end
What is going wrong with my code?
The gets() method returns an object of type String.
When you call %() on a String object, the return value is a new String object (usually it changes the text. You can read more about string formatting here).
Since there are no String objects that == 0, the if/else will always take the same path.
If you want to use the return value of gets() like a number, you will need to transform it into one first. The simplest approach is probably to use the to_i() method on String objects, which returns a new 'Integer' object. If you're doing something where the user input will not always be an integer (e.g. 3.14 or 1.5), you might need to use a different approach.
One last thing: in your example the result of gets() is saved into a constant called TestNumber. Constants are different to normal variables, and they will probably cause problems if you're not using them intentionally. Normal variables don't start with capital letters. (You can read more about ruby variables here). In ruby you need to write you variable names like this: test_number.
I suspect your Testnumber variable might be interpreted as a string during the operation. make sure the testnum is converted to an integer first even if you put in say 100 it could be its being interpreted as the stirng "100" and not the integer 100.
A similar issue can be found here: Ruby Modulo Division
You have to convert TestNumber from string to integer, as your input has linefeed and/or other unwanted characters that do not match an integer.
Use TestNumber = gets.to_i to convert to integer before testing.
I am wondering how to make something where if X=5 and Y=2, then have it output something like
Hello 2 World 5.
In Java I would do
String a = "Hello " + Y + " World " + X;
System.out.println(a);
So how would I do that in TI-BASIC?
You have two issues to work out, concatenating strings and converting integers to a string representation.
String concatenation is very straightforward and utilizes the + operator. In your example:
"Hello " + "World"
Will yield the string "Hello World'.
Converting numbers to strings is not as easy in TI-BASIC, but a method for doing so compatible with the TI-83+/84+ series is available here. The following code and explanation are quoted from the linked page:
:"?
:For(X,1,1+log(N
:sub("0123456789",ipart(10fpart(N10^(-X)))+1,1)+Ans
:End
:sub(Ans,1,length(Ans)-1?Str1
With our number stored in N, we loop through each digit of N and store
the numeric character to our string that is at the matching position
in our substring. You access the individual digit in the number by
using iPart(10fPart(A/10^(X, and then locate where it is in the string
"0123456789". The reason you need to add 1 is so that it works with
the 0 digit.
In order to construct a string with all of the digits of the number, we first create a dummy string. This is what the "? is used
for. Each time through the For( loop, we concatenate the string from
before (which is still stored in the Ans variable) to the next numeric
character that is found in N. Using Ans allows us to not have to use
another string variable, since Ans can act like a string and it gets
updated accordingly, and Ans is also faster than a string variable.
By the time we are done with the For( loop, all of our numeric characters are put together in Ans. However, because we stored a dummy
character to the string initially, we now need to remove it, which we
do by getting the substring from the first character to the second to
last character of the string. Finally, we store the string to a more
permanent variable (in this case, Str1) for future use.
Once converted to a string, you can simply use the + operator to concatenate your string literals with the converted number strings.
You should also take a look at a similar Stack Overflow question which addresses a similar issue.
For this issue you can use the toString( function which was introduced in version 5.2.0. This function translates a number to a string which you can use to display numbers and strings together easily. It would end up like this:
Disp "Hello "+toString(Y)+" World "+toString(X)
If you know the length of "Hello" and "World," then you can simply use Output() because Disp creates a new line after every statement.
I have MATLAB set to record three webcams at the same time. I want to capture and save each feed to a file and automatically increment it the file name, it will be replaced by experiment_0001.avi, followed by experiment_0002.avi, etc.
My code looks like this at the moment
set(vid1,'LoggingMode','disk');
set(vid2,'LoggingMode','disk');
avi1 = VideoWriter('X:\ABC\Data Collection\Presentations\Correct\ExperimentA_002.AVI');
avi2 = VideoWriter('X:\ABC\Data Collection\Presentations\Correct\ExperimentB_002.AVI');
set(vid1,'DiskLogger',avi1);
set(vid2,'DiskLogger',avi2);
and I am incrementing the 002 each time.
Any thoughts on how to implement this efficiently?
Thanks.
dont forget matlab has some roots to C programming language. That means things like sprintf will work
so since you are printing out an integer value zero padded to 3 spaces you would need something like this sprintf('%03d',n) then % means there is a value to print that isn't text. 0 means zero pad on the left, 3 means pad to 3 digits, d means the number itself is an integer
just use sprintf in place of a string. the s means String print formatted. so it will output a string. here is an idea of what you might do
set(vid1,'LoggingMode','disk');
set(vid2,'LoggingMode','disk');
for (n=1:2:max_num_captures)
avi1 = VideoWriter(sprintf('X:\ABC\Data Collection\Presentations\Correct\ExperimentA_%03d.AVI',n));
avi2 = VideoWriter(sprintf('X:\ABC\Data Collection\Presentations\Correct\ExperimentB_002.AVI',n));
set(vid1,'DiskLogger',avi1);
set(vid2,'DiskLogger',avi2);
end
I'm about to build a program written in pseudocode. I've already done most of the work , but I'm stuck on the code and I don't know what to do exactly. im a begginer and not everything is clear to me ...in one of the tasks i have to do , i have to make the program ask for the players name , which will be stored as a string then the program has to check if it exceeds the limit between 2/20 characters and inform the user if the input is wrong . i have researched and tried to figure out how i might be able to fix my code but i have a really short amount of time left and coudn't find anything regarding my problem :/ . this is the code ive done for this specific task. i know its wrong but i just dont know how to fix it . any help with be much appreciated . Thanks in advance :)
pseudocode:
// Getting user's name
valid = false
loop until valid is equal to true
Output" please enter your name "
Input playName
If (playName is => 1)AND(=<20)then
Valid = true
Otherwise
output "name exceeds the character limit"
I'm not sure what the syntax of your pseudo code is but :
assuming tabulation has meaning, you may have forgot to indent some lines to include them in the loop
'valid' is first declared with a lower case first letter so you may continue referencing it same way in line "Valid = true" -> "valid = true"
In the 'If' you want to test the lenght of the String and not compare the string to an int so maybe call a function length(String) that would return the length of the string or access a string.length attribute (as you wish in pseudo code)
You want the playName to be superior or equal to 2 "length(playName) >= 2" and inferior or equal to 20 "length(playname) <= 20"
The commonly used keyword meaning Otherwise is 'Else' as in
IF (Condition) THEN (code) ELSE (code)
I may modify you code like this :
// Getting user's name
valid = false
loop until valid is equal to true
Output" please enter your name "
Input playName
If (length(playName) >= 2) AND (length(playName) <= 20)
Then
valid = true
Else
output "name exceeds the character limit"
Is it possible to use variables in both fields of the gsub method ?
I'm trying to get this piece of code work :
$I = 0
def random_image
$I.to_s
random = rand(1).to_s
logo = File.read('logo-standart.txt')
logo_aleatoire = logo.gsub(/#{$I}/, random)
File.open('logo-standart.txt', "w") {|file| File.puts logo_aleatoire}
$I.to_i
$I += 1
end
Thanks in advance !
filecontents = File.read('logo-standart.txt')
filecontents.gsub!(/\d+/){rand(100)}
File.open("logo-standart.txt","w"){|f| f << filecontents }
The magic line is the second line.
The gsub! function modifies the string in-place, unlike the gsub function, which would return a new string and leave the first string unmodified.
The single parameter that I passed to gsub! is the pattern to match. Here, the goal is to match any string of one or more digits -- this is the number that you're going to replace. There's no need to loop through all of the possible numbers running gsub on each one. You can even match numbers as high as a googol (or higher) without your program taking longer and longer to run.
The block that gsub! takes is evaluated each time the pattern matches to programmatically generate a replacement number. So each time, you get a different random number. This is different from the more usual form of gsub! that takes two parameters -- there the parameter is evaluated once before any pattern matching occurs, and all matches are replaced by the same string.
Note that the way this is structured, you get a new random number for each match. So if the number 307 appears twice, it turns into two different random numbers.
If you wanted to map 307 to the same random number each time, you could do the following:
filecontents = File.read('logo-standart.txt')
randomnumbers = Hash.new{|h,k| h[k]=rand(100)}
filecontents.gsub!(/\d+/){|match| randomnumbers[match]}
File.open("logo-standart.txt","w"){|f| f << filecontents }
Here, randomnumbers is a hash that lets you look up the numbers and find what random number they correspond to. The block passed when constructing the hash tells the hash what to do when it finds a number that it hasn't seen before -- in this case, generate a new random number, and remember what that random number the mapping. So gsub!'s block just asks the hash to map numbers for it, and randomnumbers takes care of generating a new random number when you encounter a new number from the original file.