I am trying to making print statement work in Pluto.jl. Right now when I execute println it prints to console, using PlutoUI extension to makes the print statement work but not in for loop.
Is there a way to print in for loop to Pluto.jl notebook?
You can use with_terminal() like so:
(the code is:
using PlutoUI
with_terminal() do
for i in 1:10
println("Hi, I'm $i")
end
end
Related
I have created a "while" loop that looks like this:
x <- 2
while (x < 8) {
print("Shrek")
}
Now, I have tried breaking the loop by inserting break in to the while loop, like this:
while (x < 8) {
print("Shrek")
break
}
but this doesn't break the loop, the console just keeps printing "Shrek".
How can i make it stop? Have I put break in the wrong place?
Side question: Can there arise any problems from exiting Rstudio while it's in an on-going while() loop like this?
Thanks!
Edit:
Pressing escape stopped the loop. Is there any line of code in the console that also stops it?
Based on the code you have given I can't reproduce this. When I run everything, break works just fine. Have you potentially defined a variable called 'break' that would have overridden the default function? If not try resetting R and running this again.
I've written a prime-generating function generatePrimes (full code here) that takes input bound::Int64 and returns a Vector{Int64} of all primes up to bound. After the function definition, I have the following code:
println("Generating primes...")
println("Last prime: ", generatePrimes(10^7)[end])
println("Primes generated.")
which prints, unexpectedly,
Generating primes...
9999991
Primes generated.
This output misses the "Last prime: " segment of the second print statement. The output does work as expected for smaller inputs; any input at least up to 10^6, but somehow fails for 10^7. I've tried several workarounds for this (e.g. assigning the returned value or converting it to a string before calling it in a print statement, combining the print statements, et cetera) and discovered some other weird behaviour: if the "Last prime", is removed from the second print statement, for input 10^7, the last prime doesn't print at all and all I get is a blank line between the first and third print statements. These issues are probably related, and I can't seem to find anything online about why some print statements wouldn't work in Julia.
Thanks so much for any clarification!
Edit: Per DNF's suggestion, following are some reductions to this issue:
Removing the first and last print statements doesn't change anything -- a blank line is always printed in the case I outlined and each of the cases below.
println(generatePrimes(10^7)[end]) # output: empty line
Calling the function and storing the last index in a variable before calling println doesn't change anything either; the cases below work exactly the same either way.
lastPrime::Int = generatePrimes(10^7)[end]
println(lastPrime) # output: empty line
If I call the function in whatever form immediately before a println, an empty line is printed regardless of what's inside the println.
lastPrime::Int = generatePrimes(10^7)[end]
println("This doesn't print") # output: empty line
println("This does print") # output: This does print
If I call the function (or print the pre-generated-and-stored function result) inside a println, anything before the function call (that's also inside the println) isn't printed. The 9999991 and anything else there may be after the function call is printed only if there is something else inside the println before the function call.
# Example 1
println(generatePrimes(10^7)[end]) # output: empty line
# Example 2
println("This first part doesn't print", generatePrimes(10^7)[end]) # output: 9999991
# Example 3
println("This first part doesn't print", generatePrimes(10^7)[end], " prints") # output: 9999991 prints
# Example 4
println(generatePrimes(10^7)[end], "prime doesn't print") # output: prime doesn't print
I could probably list twenty different variations of this same thing, but that probably wouldn't make things any clearer. In every single case version of this issue I've seen so far, the issue only manifests if there's that function call somewhere; println prints large integers just fine. That said, please let me know if anyone feels like they need more info. Thanks so much!
Most likely you are running this code from Atom Juno which recently has some issues with buffering standard output (already reported by others and I also sometimes have this problem).
One thing you can try to do is to flush your standard output
flush(stdout)
Like with any unstable bug restarting Atom Juno also seems to help.
I had the same issue. For me, changing the terminal renderer (File -> Settings -> Packages -> julia-client -> Terminal Options) from webgl to canvas (see pic below) seems to solve the issue.
change terminal renderer
I've also encountered this problem many times. (First time, it was triggered after using the debugger. It is probably unrelated but I have been using Julia+Juno for 2 weeks prior to this issue.)
In my case, the code before the println statement needed to have multiple dictionary assignation (with new keys) in order to trigger the behavior.
I also confirmed that the same code ran in Command Prompt (with same Julia interpreter) prints fine. Any hints about how to further investigate this will be appreciated.
I temporarily solve this issue by printing to stderr, thinking that this stream has more stringent flush mechanism: println(stderr, "hello!")
I wrote a function that outputs a single element numeric after a 300-cycle for loop. I make it print about 10 lines in each cycle, to know where it's at. Now I want to run this for loop itself in a 1000 cycle for loop (and place the resulting numbers in a matrix). But it prints way to much stuff and I don't know where it's at in the execution of the outer (1000 cycle) for loop. The output from the inner for loop overwhelms a print statement executed at each of the outer loop's cycles. Here's how it looks:
for(i in 1:1000){
function(...){...} #prints 10 lines 300 times before outputting a single element numeric
cat("Outer loop step "); print(i)}
Now I don't want to remove the print statements from my function, but I want to mute them when I call the function in that for loop. How can I run my function without executing it's print() statements?
Modify your function so you can pass in a "debug" true/false parameter to control the print statements.
Don't use print or cat. Use message instead. You can then use suppressMessages to suppress the message output.
How can output to stdout be suppressed?
A semi-colon can be used to supress display of returned objects, for example
>>> 1+1
2
>>> 1+1; # No output!
However, a function that prints to stdout is not affected by the semi-colon.
>>> print('Hello!')
Hello!
>>> MyFunction()
Calculating values...
How can the output from print / MyFunction be suppressed?
Add %%capture as the first line of the cell. eg
%%capture
print('Hello')
MyFunction()
This simply discards the output, but the %%capture magic can be used to save the output to a variable - consult the docs
Suppress output
Put a ; at the end of a line to suppress the printing of output [Reference].
A good practice is to always return values from functions rather than printing values inside a function. In that case, you have the control; if you want to print the returned value, you can; otherwise, it will not be printed just by adding a ; after the function call.
(credit: https://stackoverflow.com/a/23611571/389812)
You could use io.capture_output:
from IPython.utils import io
with io.capture_output() as captured:
MyFunction()
to supress (e.g. capture) stdout and stderr for those lines within the with-statement.
If anyone is interested in clearing all outputs:
Go to Cell
Go to All Output
Then choose whichever option you like.
Is it possible to have gdb log something to the terminal instead of breaking on it? For example I would like to set a 'breakpoint' on some method and have gdb print self as well as the parameters each time the method is invoked. Basically I want to insert print statements into arbitrary places without actually recompiling.
thanks for any suggestions
This is what i have so far after these helpful comments:
define logFoo
b fooMethod
commands
po self
end
end
GDB doesn't seem to like the nested end statements though. any thoughts?
You can use Breakpoint Command Lists. There is an example how to do it.
For example, here is how you could use
breakpoint commands to print the value
of x at entry to foo whenever x is
positive.
break foo if x>0
commands
silent
printf "x is %d\n",x
cont
end
Use a breakpoint as usual, and set a macro to log and continue:
define c
print "foo"
cont
c
end
No, this is not possible. You can only hook into the symbols of the code and machine code. If you want to log output you will need a logging functionality.
If you are tracing specific errors try conditional breakpoints and watch variables.
EDIT:
Even while not directly loggin it could be an alternative to use GDB command files