I'm trying to make a simple lua program that converts Fahrenheit to Celsius and kelvin and I don't know how to put an input command on the same line as a print line. Here's what I mean.
I want the program to display:
Fahrenheit = "Here's the user input"
I know how to make it say
Fahrenheit =
"User input"
I'm still a novice.
This is my code so far:
print("Fahrenheit = ") f = io.read() c = (5/9)*(f-32)
print("Celsius = "..c) k = c + 273 print("Kelvin = "..k)
Look into io.write() and io.read(). For instance, you could say:
io.write("Fahrenheit = ")
The write command writes output to the screen buffer, but doesn't add a newline. Similarly, read checks the latest input, and returns it.
For reference, I suggest this link from the tutorial.
Related
I have the following code.
import lib
var stat = false
when isMainModule:
while stat != true:
echo("Option: ")
var opt = readChar(stdin)
case opt
of 'q':
stat = true
of 'n':
echo("Salu: ")
var ss = readLine(stdin)
echo("Nam: ")
var nn = readLine(stdin)
let k = prompt("Rust")
else: discard
What I am trying to achieve is, prompting and receiving user input one after another for two variables. Upon choosing n I am expecting Salu first and once user input is supplied then Nam.
However, what I receive when I execute the following nim code by issuing the following command is, nim c -r src/mycode.nim
~~> nim c -r src/cmdparsing.nim
...
...
...
CC: stdlib_system.nim
CC: cmdparsing.nim
Hint: [Link]
Hint: operation successful (48441 lines compiled; 2.338 sec total; 66.824MiB peakmem; Debug Build) [SuccessX]
Hint: /home/XXXXX/Development/nim_devel/mycode/src/mycode [Exec]
Option:
n
Salu:
Nam:
Salu is being echoed, but readLine doesn't wait for my input and immediately echoes Nam. But, stacked readLine commands from the prompt procedure appears one after the other for receiving user input.
I was wondering what is that I am missing to understand here. Could someone enlighten me?
Code for prompt lives in lib.nim which is as follows,
proc prompt*(name: string): bool =
echo("Salutation: ")
var nn = readLine(stdin)
echo(nn&"."&name)
echo("Diesel")
var dd = readLine(stdin)
echo(dd)
return true
You do a readChar to get the opt value, and then you input two chars: n and \n. The first is the opt value, the second gets buffered or retained in the stdin waiting for further reading. The next time you try to read a line, the \n that's still hanging is interpreted as a new line, and immediately assigned to ss. You don't see anything because the line is empty except for the newline char.
E.g.
var opt = readChar(stdin)
case opt
of 'n':
var ss = readLine(stdin)
echo ss
else:
discard
Compile and run, but in the input write something like "ntest". n fires the first branch of case, test (the remainder of stdin) is assigned to ss, and echoed.
You have two options to solve the problem:
Read a line instead of a char, and store only the first char with something like var opt = readLine(stdin)[0].
Use the rdstdin module:
import rdstdin
var ss = readLineFromStdin("Salu:")
So I'm trying to make a lottery program where you pick a animal, letter, and number, those are put into a array and compared to another that has the parts chosen by random.
Testing with what I call the animal round.
I have a while loop for invalid entries, that it will not move on till one of the four animals is accepted. But when it does that, the variable invalid goes to false and the coding after it doesn't get used at all. I had this problem last night, and when I finally gave up and went to bed, I decided I'll write it out on flowgorithm (If you haven't heard it makes a flow chart and you can go through programming with it step by step).
I made it, and it worked like expected, I copy and paste it over, and I get the exact same problem as last night.
Here is the code.
#import library
import random
#get variables
game = True
invalid = True
animalarray = [""]
animalarray.append("tiger")
animalarray.append("cow")
animalarray.append("turtle")
animalarray.append("bird")
lotteryarray = [""]
#game loop
#animal round
print("Pick a animal: ")
print("tiger")
print("cow")
print("turtle")
print("bird")
print(" ")
lotteryarray[0] = input()
#while loop for invalid entry
while invalid == True:
if lotteryarray[0] == "tiger" or lotteryarray[0] == "cow" or lotteryarray[0] == "turtle" or lotteryarray[0] == "bird":
invalid == False
else:
print("Invalid entry!")
lotteryarray[0] = input()
print(" ")
print("You chose " + lotteryarray[0])
game == False
And this is all I get in the shell:
Pick a animal:
tiger
cow
turtle
bird
tiger
the tiger there is what I put in, it isn't being printed.
And here is the flowgorithm, like I said, in flowgorithm this works.
flowgorithm of lottery game
I figured it out.
I printed what invalid was after it was meant to change to False and it didn't change, I changed the two equal signs to one and it worked and changed the value.
I'm writing an LPeg-based parser. How can I make it so a parsing error returns nil, errmsg?
I know I can use error(), but as far as I know that creates a normal error, not nil, errmsg.
The code is pretty long, but the relevant part is this:
local eof = lpeg.P(-1)
local nl = (lpeg.P "\r")^-1 * lpeg.P "\n" + lpeg.P "\\n" + eof -- \r for winblows compat
local nlnoeof = (lpeg.P "\r")^-1 * lpeg.P "\n" + lpeg.P "\\n"
local ws = lpeg.S(" \t")
local inlineComment = lpeg.P("`") * (1 - (lpeg.S("`") + nl * nl)) ^ 0 * lpeg.P("`")
local wsc = ws + inlineComment -- comments count as whitespace
local backslashEscaped
= lpeg.P("\\ ") / " " -- escaped spaces
+ lpeg.P("\\\\") / "\\" -- escaped escape character
+ lpeg.P("\\#") / "#"
+ lpeg.P("\\>") / ">"
+ lpeg.P("\\`") / "`"
+ lpeg.P("\\n") -- \\n newlines count as backslash escaped
+ lpeg.P("\\") * lpeg.P(function(_, i)
error("Unknown backslash escape at position " .. i) -- this error() is what I wanna get rid of.
end)
local Line = lpeg.C((wsc + (backslashEscaped + 1 - nl))^0) / function(x) return x end * nl * lpeg.Cp()
I want Line:match(...) to return nil, errmsg when there's an invalid escape.
LPeg itself doesn't provide specific functions to help you with error reporting. A quick fix to your problem would be to make a protected call (pcall) to match like this:
local function parse(text)
local ok, result = pcall(function () return Line:match(text) end)
if ok then
return result
else
-- `result` will contain the error thrown. If it is a string
-- Lua will add additional information to it (filename and line number).
-- If you do not want this, throw a table instead like `{ msg = "error" }`
-- and access the message using `result.msg`
return nil, result
end
end
However, this will also catch any other error, which you probably don't want. A better solution would be to use LPegLabel instead. LPegLabel is an extension of LPeg that adds support for labeled failures. Just replace require"lpeg" with require"lpeglabel" and then use lpeg.T(L) to throw labels where L is an integer from 1-255 (0 is used for regular PEG failures).
local unknown_escape = 1
local backslashEscaped = ... + lpeg.P("\\") * lpeg.T(unknown_escape)
Now Line:match(...) will return nil, label, suffix if there is a label thrown (suffix is the remaining unprocessed input, which you can use to compute for the error position via its length). With this, you can print out the appropriate error message based on the label. For more complex grammars, you would probably want a more systematic way of mapping the error labels and messages. Please check the documentation found in the readme of the LPegLabel repository to see examples of how one may do so.
LPegLabel also allows you to catch the labels in the grammar by the way (via labeled choice); this is useful for implementing things like error recovery. For more information on labeled failures and examples, please check the documentation.
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.
I'm brand new to TCL, and am trying to wrap my brain around all the usages of "", {}, and [] that it uses. Something I'm used to doing in other languages is defining my variables prior to use, at the beginning of the application. The below code works:
puts "Please enter an integer of choice to be added: "
flush stdout
gets stdin intAnswer
puts "Please enter a second integer of choice to be added: "
flush stdout
gets stdin intAnswerTwo
puts "Please enter a third integer of choice to be added: "
flush stdout
gets stdin intAnswerThree
puts "The total of the three integers is: [expr $intAnswer + $intAnswerTwo + $intAnswerThree]"
What I'm wanting to do is define the variables prior to use. As such:
set intAnswer 0
set intAnswerTwo 0
set intAnswerThree 0
set intTotal 0
This code, placed at the beginning, doesn't work with the rest of the code. What am I missing?
The code looks absolutely fine to me, though [expr {$intAnswer + $intAnswerTwo + $intAnswerThree}] would be better (as it stops potential reinterpretation of the variables' contents, which would be both a safety and performance issue).
However, if you really want to have integers from the user, you need to validate their input. This is most easily done by writing a procedure to do the job so you can reuse it (i.e., you refactor the code to get a value so you can use a more sophisticated version and get it right once):
proc getIntFromUser {message} {
# Loop forever (until we [exit] or [return $response])
while true {
puts $message
flush stdout
set response [gets stdin]
# Important to check for EOF...
if {[eof stdin]} {
exit
}
# The validator (-strict is needed for ugly historical reasons)
if {[string is integer -strict $response]} {
return $response
}
# Not an integer, so moan about it
puts "\"$response\" is not an integer!"
}
}
Now you have that procedure, the rest of your code can become:
set intAnswer [getIntFromUser "Please enter an integer of choice to be added: "]
set intAnswerTwo [getIntFromUser "Please enter a second integer of choice to be added: "]
set intAnswerThree [getIntFromUser "Please enter a third integer of choice to be added: "]
puts "The total of the three integers is: [expr {$intAnswer + $intAnswerTwo + $intAnswerThree}]"
The art of writing good Tcl code (or good code in pretty much any other language) is knowing what are the good points to refactor. A good starting point is “if you do it twice or more, do it once and share”. It's doubly good if you can give the procedure a good name and clear interface, a clear indication that you've got it right. Indeed, you could also go for:
set total [expr {
[getIntFromUser "Please enter an integer of choice to be added: "] +
[getIntFromUser "Please enter a second integer of choice to be added: "] +
[getIntFromUser "Please enter a third integer of choice to be added: "]
}]
puts "The total of the three integers is: $total"
The results observed by the user will be identical.