Sorbet infers the type of true to be TrueClass, and the type of false to be FalseClass. Often it would be nice if it would instead infer T::Boolean. Why not special case true and false to have the type T::Boolean instead?
It's possible to work around this problem with a type annotation, initializing variables with T.let(true, T::Boolean) for example, but it would be nice to not have to provide this extra information.
# typed: true
T.reveal_type(true) # Revealed type: `TrueClass`
T.reveal_type(false) # Revealed type: `FalseClass`
extend T::Sig
sig {params(x: T::Boolean).void}
def test(x)
var = true
10.times do
var = false # Changing the type of a variable in a loop is not permitted
end
end
The assignment of false to var in the loop causes an error to be raised, as the type of var is being changed from TrueClass to FalseClass.
Sorbet's flow-sensitive typing is made more precise by true and false having different types. In the following example, a variable with the value true is used as the condition of an if-statement:
# typed: true
val = true
if val
puts "true!"
else
puts "false?"
end
The resulting error from sorbet is:
editor.rb:7: This code is unreachable https://srb.help/7006
7 | puts "false?"
^^^^^^^^
Errors: 1
Behind the scenes, sorbet knows that the value being examined has the type TrueClass, and that the value true is the only value of that type. As a result, it knows that val cannot be false, and that the else branch will never be executed.
Now consider the case where we instead infer the type T::Boolean for true and false. T::Boolean is a synonym for T.any(TrueClass, FalseClass), so in the example it now means that val could be either true or false. As a result, it becomes impossible to tell from the type alone that the else branch will not be executed.
The flow-sensitive typing documentation on sorbet.org has more information on this topic.
Asked the same question today as well.
Ended up fixing it as you suggested with type annotations and initializing with T.let(true, T::Boolean)
# typed: true
extend T::Sig
sig {params(x: T::Boolean).void}
def test(x)
var = T.let(true, T::Boolean)
10.times do
var = T.let(false, T::Boolean)
end
end
I'm trying to create a little menu to switch from "YouCompleteMe" to "Supertab" and vice versa.
function! TabFunction()
if !exists("g:WhatTab")
let g:WhatTab = "Tab function?"
endif
if !exists("g:MenuTab_choices")
let g:MenuTab_choices = "&SuperTab\n&YouCompleteMe"
endif
let n = confirm(g:WhatTab, g:MenuTab_choices, "Question")
if n == 1
let g:SuperTabMappingForward = '<Tab>'
let g:SuperTabMappingBackward = '<S-Tab>'
let g:ycm_key_list_select_completion = ['<C-Tab>', '<Down>']
let g:ycm_key_list_previous_completion = ['<C-S-Tab>', '<Up>']
elseif n == 2
let g:SuperTabMappingForward = '<C-Tab>'
let g:SuperTabMappingBackward = '<C-S-Tab>'
let g:ycm_key_list_select_completion = ['<Tab>', '<Down>']
let g:ycm_key_list_previous_completion = ['<S-Tab>', '<Up>']
endif
endfun
This doesn't work.
When I try to check the value of these variables from the commandline
:echo 'global variable'
the values are correct but they don't work as expected.
Is it not possible to declare a global variable like this?
The use of the g: variable prefix ensures that the global variables are set from within a function; this is correct. Your problem is that the plugin configuration variables like g:SuperTabMappingForward are only evaluated once during plugin load (when Vim starts up), but not during runtime. This mechanism wasn't meant for dynamic reconfiguration.
Solutions
Instead of toggling the (ignored) config variables, you have to do the remapping yourself. At least SuperTab defines corresponding <Plug>... targets; I guess YCM does this, too:
if n == 1
imap <Tab> <Plug>SuperTabForward
...
elseif n == 2
imap <C-Tab> <Plug>SuperTabForward
Alternatively, the brute-force variant would be to reload the plugins (:runtime plugin/supertab.vim) to get the changed global variable values to be considered, but that's very inefficient, may cause errors, and makes you work around plugin load guards in addition.
I have a problem with addEventListener "touch". When two or more object are located nearby and activated with one "touch" only one object hits the endded phase.
What I've tried:
function theBall(event)
local ball = event.target.id.id
if event.phase == "began" then
print("began")
display.getCurrentStage():setFocus(event.target)
end
if event.phase == "ended" or event.phase == "cancelled" then
print("ended")
display.getCurrentStage():setFocus(nil)
end
end
invisibleBall[ball]:addEventListener( "touch", theBall)
in simulator output:
began
began
began
ended
You need to do a:
return true
at the end of your function, if not the event propagates to any objects below it. This is by design. Just put that return true before the last end and you will be all taken care of.
Situation :
There are two sensors and I want to save the data of values of each sensor in the certain file..But it's not working. I am working on linux system and the file is still empty.
What's wrong with my code? any suggestion please?
my code is:
--Header file
require("TIMER")
require("TIMESTAMP")
require("ANALOG_IN")
function OnExit()
print("Exit code...do something")
end
function main()
timer = "TIMER"
local analogsensor_1 = "AIR_1"
local analogsensor_2 = "AIR_2"
local timestr = os.data("%Y-%m-%d %H:%M:%S")
-- open the file for writing binary data
local filehandle = io.open("collection_of_data.txt", "a")
while true do
valueOfSensor_1 = ANALOG_IN.readAnalogIn(analogsensor_1);
valueOfSensor_2 = ANALOG_IN.readAnalogIn(analogsensor_2);
if (valueOfSensor_1 > 0 and valueOfSensor_2 > 0) then
-- save values of sensors
filehandle:write(timestr, " -The Value of the Sensors: ", tostring(valueOfSensor_1), tostring(valueOfSensor_2)"\n");
end
TIMER.sleep(timer,500)
end
-- close the file
filehandle:close()
end
print("start main")
main()
I do not know what this libs realy do.
But this code is incorrect;
1) you do not close while statement.
if in real code you close it before filehandle:close() then try call filehandle:flush()
2) you forgot comma:
filehandle:write(timestr, " -The Value of the Sensors: ", tostring(valueOfSensor_1), tostring(valueOfSensor_2)"\n")
(it should seay something like attemt call a number value).
3) try print out valueOfSensor_1 and valueOfSensor_2 values. May be there no data.
Beside the typos pointed out by #moteus, shouldn't this:
if (valueOfSensor_1 and valueOfSensor_2 > 0) then
be like this?
if (valueOfSensor_1 > 0 and valueOfSensor_2 > 0) then
Edit, in response to your comment to another answer:
still error..it says "attempt to call field 'data' (a nil value)
I can't be sure without the stack trace, but, most likely, something bad happens in the ANALOG_IN library code. You may not be using it properly.
try to turn this:
valueOfSensor_1 = ANALOG_IN.readAnalogIn(analogsensor_1);
valueOfSensor_2 = ANALOG_IN.readAnalogIn(analogsensor_2);
into this:
success, valueOfSensor_1 = pcall(ANALOG_IN.readAnalogIn, analogsensor_1);
if not success then
print("Warning: error reading the value of sensor 1:\n"..valueOfSensor_1)
valueOfSensor_1 = 0
end
success, valueOfSensor_2 = pcall(ANALOG_IN.readAnalogIn, analogsensor_2);
if not success then
print("Warning: error reading the value of sensor 2:\n"..valueOfSensor_2)
valueOfSensor_2 = 0
end
If the failure in ANALOG_IN is not systematic, it will work around it. If the call fails systematically, you'll get a huge warning log, and an empty collection_of_data.txt.
Please note that ANALOG_IN is not a standard Lua library. You should check its documentation , and pay attention to the details of its usage.
How can I check if a file exists using Lua?
Try
function file_exists(name)
local f=io.open(name,"r")
if f~=nil then io.close(f) return true else return false end
end
but note that this code only tests whether the file can be opened for reading.
Using plain Lua, the best you can do is see if a file can be opened for read, as per LHF. This is almost always good enough. But if you want more, load the Lua POSIX library and check if posix.stat(path) returns non-nil.
Lua 5.1:
function file_exists(name)
local f = io.open(name, "r")
return f ~= nil and io.close(f)
end
I will quote myself from here
I use these (but I actually check for the error):
require("lfs")
-- no function checks for errors.
-- you should check for them
function isFile(name)
if type(name)~="string" then return false end
if not isDir(name) then
return os.rename(name,name) and true or false
-- note that the short evaluation is to
-- return false instead of a possible nil
end
return false
end
function isFileOrDir(name)
if type(name)~="string" then return false end
return os.rename(name, name) and true or false
end
function isDir(name)
if type(name)~="string" then return false end
local cd = lfs.currentdir()
local is = lfs.chdir(name) and true or false
lfs.chdir(cd)
return is
end
os.rename(name1, name2) will rename name1 to name2. Use the same name and nothing should change (except there is a badass error). If everything worked out good it returns true, else it returns nil and the errormessage. If you dont want to use lfs you cant differentiate between files and directories without trying to open the file (which is a bit slow but ok).
So without LuaFileSystem
-- no require("lfs")
function exists(name)
if type(name)~="string" then return false end
return os.rename(name,name) and true or false
end
function isFile(name)
if type(name)~="string" then return false end
if not exists(name) then return false end
local f = io.open(name)
if f then
f:close()
return true
end
return false
end
function isDir(name)
return (exists(name) and not isFile(name))
end
It looks shorter, but takes longer...
Also open a file is a it risky
Have fun coding!
If you're using Premake and LUA version 5.3.4:
if os.isfile(path) then
...
end
For sake of completeness: You may also just try your luck with path.exists(filename). I'm not sure which Lua distributions actually have this path namespace (update: Penlight), but at least it is included in Torch:
$ th
______ __ | Torch7
/_ __/__ ________/ / | Scientific computing for Lua.
/ / / _ \/ __/ __/ _ \ | Type ? for help
/_/ \___/_/ \__/_//_/ | https://github.com/torch
| http://torch.ch
th> path.exists(".gitignore")
.gitignore
th> path.exists("non-existing")
false
debug.getinfo(path.exists) tells me that its source is in torch/install/share/lua/5.1/pl/path.lua and it is implemented as follows:
--- does a path exist?.
-- #string P A file path
-- #return the file path if it exists, nil otherwise
function path.exists(P)
assert_string(1,P)
return attrib(P,'mode') ~= nil and P
end
If you are willing to use lfs, you can use lfs.attributes. It will return nil in case of error:
require "lfs"
if lfs.attributes("non-existing-file") then
print("File exists")
else
print("Could not get attributes")
end
Although it can return nil for other errors other than a non-existing file, if it doesn't return nil, the file certainly exists.
An answer which is windows only checks for files and folders, and also requires no additional packages. It returns true or false.
io.popen("if exist "..PathToFileOrFolder.." (echo 1)"):read'*l'=='1'
io.popen(...):read'*l' - executes a command in the command prompt and reads the result from the CMD stdout
if exist - CMD command to check if an object exists
(echo 1) - prints 1 to stdout of the command prompt
An answer which is windows only checks for files and folders, and also requires no additional packages. It returns true or false.
You can also use the 'paths' package. Here's the link to the package
Then in Lua do:
require 'paths'
if paths.filep('your_desired_file_path') then
print 'it exists'
else
print 'it does not exist'
end
Not necessarily the most ideal as I do not know your specific purpose for this or if you have a desired implementation in mind, but you can simply open the file to check for its existence.
local function file_exists(filename)
local file = io.open(filename, "r")
if (file) then
-- Obviously close the file if it did successfully open.
file:close()
return true
end
return false
end
io.open returns nil if it fails to open the file. As a side note, this is why it is often used with assert to produce a helpful error message if it is unable to open the given file. For instance:
local file = assert(io.open("hello.txt"))
If the file hello.txt does not exist, you should get an error similar to stdin:1: hello.txt: No such file or directory.
For library solution, you can use either paths or path.
From the official document of paths:
paths.filep(path)
Return a boolean indicating whether path refers to an existing file.
paths.dirp(path)
Return a boolean indicating whether path refers to an existing directory.
Although the names are a little bit strange, you can certainly use paths.filep() to check whether a path exists and it is a file. Use paths.dirp() to check whether it exists and it is a directory. Very convenient.
If you prefer path rather than paths, you can use path.exists() with assert() to check the existence of a path, getting its value at the same time. Useful when you are building up path from pieces.
prefix = 'some dir'
filename = assert(path.exist(path.join(prefix, 'data.csv')), 'data.csv does not exist!')
If you just want to check the boolean result, use path.isdir() and path.isfile(). Their purposes are well-understood from their names.
If you use LOVE, you can use the function love.filesystem.exists('NameOfFile'), replacing NameOfFile with the file name.
This returns a Boolean value.
How about doing something like this?
function exist(file)
local isExist = io.popen(
'[[ -e '.. tostring(file) ..' ]] && { echo "true"; }')
local isIt = isExist:read("*a")
isExist:close()
isIt = string.gsub(isIt, '^%s*(.-)%s*$', '%1')
if isIt == "true" then
return true
end
return false
end
if exist("myfile") then
print("hi, file exists")
else
print("bye, file does not exist")
end
if you are like me exclusively on Linux, BSD any UNIX type you can use this:
function isDir(name)
if type(name)~="string" then return false end
return os.execute('if [ -d "'..name..'" ]; then exit 0; else exit 1; fi')
end
function isFile(name)
if type(name)~="string" then return false end
return os.execute('if [ -f "'..name..'" ]; then exit 0; else exit 1; fi')
end
Actually this looks even better:
function isDir(name)
if type(name)~="string" then return false end
return os.execute('test -d '..name)
end
function isFile(name)
if type(name)~="string" then return false end
return os.execute('test -f '..name)
end
function exists(name)
if type(name)~="string" then return false end
return os.execute('test -e '..name)
end
IsFile = function(path)
print(io.open(path or '','r')~=nil and 'File exists' or 'No file exists on this path: '..(path=='' and 'empty path entered!' or (path or 'arg "path" wasn\'t define to function call!')))
end
IsFile()
IsFile('')
IsFIle('C:/Users/testuser/testfile.txt')
Looks good for testing your way. :)