How should the forever function be used?
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I have a function. Let's say it looks like this:
strangeFunc = do
putStrLn "Welcome to the game! Please, enter the name of the file: "
--some more code
Then, I want it to run forever, so I do this
strangeFunc = forever $ do
putStrLn "Welcome to the game! Please, enter the name of the file: "
--some more code
But I have an error: variable not in scope: forever. How can I fix it?
haskell
edited Nov 23 '18 at 19:11
AJFarmar
9,34722954
asked Nov 23 '18 at 18:13
Kada FuiteKada Fuite
163
add a comment |
I have a function. Let's say it looks like this:
strangeFunc = do
putStrLn "Welcome to the game! Please, enter the name of the file: "
--some more code
Then, I want it to run forever, so I do this
strangeFunc = forever $ do
putStrLn "Welcome to the game! Please, enter the name of the file: "
--some more code
But I have an error: variable not in scope: forever. How can I fix it?
haskell
edited Nov 23 '18 at 19:11
AJFarmar
9,34722954
asked Nov 23 '18 at 18:13
Kada FuiteKada Fuite
163
1
A side note:foreveris not a monad, it is a function.
– AJFarmar
Nov 23 '18 at 18:20
Your example has no variables, so we don't know why there's a variable out of scope. That just means you're referring to some variable that is unknown (in that context).
– Jorge Adriano
Nov 23 '18 at 18:59
1
Also while you can useforever, if running something forever is confusing you this much, maybe you should be trying to do it without resorting toforeverfirst, for instructional purposes. All you need is to code an "infinite loop", i.e. write a function that "runs the code" then calls itself.
– Jorge Adriano
Nov 23 '18 at 19:02
add a comment |
I have a function. Let's say it looks like this:
strangeFunc = do
putStrLn "Welcome to the game! Please, enter the name of the file: "
--some more code
Then, I want it to run forever, so I do this
strangeFunc = forever $ do
putStrLn "Welcome to the game! Please, enter the name of the file: "
--some more code
But I have an error: variable not in scope: forever. How can I fix it?
haskell
edited Nov 23 '18 at 19:11
AJFarmar
9,34722954
asked Nov 23 '18 at 18:13
Kada FuiteKada Fuite
163
I have a function. Let's say it looks like this:
strangeFunc = do
putStrLn "Welcome to the game! Please, enter the name of the file: "
--some more code
Then, I want it to run forever, so I do this
strangeFunc = forever $ do
putStrLn "Welcome to the game! Please, enter the name of the file: "
--some more code
But I have an error: variable not in scope: forever. How can I fix it?
haskell
haskell
edited Nov 23 '18 at 19:11
AJFarmar
9,34722954
asked Nov 23 '18 at 18:13
Kada FuiteKada Fuite
163
edited Nov 23 '18 at 19:11
AJFarmar
9,34722954
asked Nov 23 '18 at 18:13
Kada FuiteKada Fuite
163
edited Nov 23 '18 at 19:11
AJFarmar
9,34722954
edited Nov 23 '18 at 19:11
AJFarmar
9,34722954
edited Nov 23 '18 at 19:11
AJFarmar
9,34722954
9,34722954
asked Nov 23 '18 at 18:13
Kada FuiteKada Fuite
163
asked Nov 23 '18 at 18:13
Kada FuiteKada Fuite
163
asked Nov 23 '18 at 18:13
Kada FuiteKada Fuite
163
163
1
A side note:foreveris not a monad, it is a function.
– AJFarmar
Nov 23 '18 at 18:20
Your example has no variables, so we don't know why there's a variable out of scope. That just means you're referring to some variable that is unknown (in that context).
– Jorge Adriano
Nov 23 '18 at 18:59
1
Also while you can useforever, if running something forever is confusing you this much, maybe you should be trying to do it without resorting toforeverfirst, for instructional purposes. All you need is to code an "infinite loop", i.e. write a function that "runs the code" then calls itself.
– Jorge Adriano
Nov 23 '18 at 19:02
add a comment |
1
A side note:foreveris not a monad, it is a function.
– AJFarmar
Nov 23 '18 at 18:20
Your example has no variables, so we don't know why there's a variable out of scope. That just means you're referring to some variable that is unknown (in that context).
– Jorge Adriano
Nov 23 '18 at 18:59
1
Also while you can useforever, if running something forever is confusing you this much, maybe you should be trying to do it without resorting toforeverfirst, for instructional purposes. All you need is to code an "infinite loop", i.e. write a function that "runs the code" then calls itself.
– Jorge Adriano
Nov 23 '18 at 19:02
1
1
A side note:
forever is not a monad, it is a function.– AJFarmar
Nov 23 '18 at 18:20
A side note:
forever is not a monad, it is a function.– AJFarmar
Nov 23 '18 at 18:20
Your example has no variables, so we don't know why there's a variable out of scope. That just means you're referring to some variable that is unknown (in that context).
– Jorge Adriano
Nov 23 '18 at 18:59
Your example has no variables, so we don't know why there's a variable out of scope. That just means you're referring to some variable that is unknown (in that context).
– Jorge Adriano
Nov 23 '18 at 18:59
1
1
Also while you can use
forever, if running something forever is confusing you this much, maybe you should be trying to do it without resorting to forever first, for instructional purposes. All you need is to code an "infinite loop", i.e. write a function that "runs the code" then calls itself.– Jorge Adriano
Nov 23 '18 at 19:02
Also while you can use
forever, if running something forever is confusing you this much, maybe you should be trying to do it without resorting to forever first, for instructional purposes. All you need is to code an "infinite loop", i.e. write a function that "runs the code" then calls itself.– Jorge Adriano
Nov 23 '18 at 19:02
add a comment |
1 Answer
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You must import forever from Control.Monad. Add this to the top of your file:
import Control.Monad (forever)
When the compiler says variable not in scope..., it means "I don't know what this is supposed to be; you haven't defined it." This can be caused by not having the required modules imported.
How did I know this? If you search for forever on Hoogle, it says that it is in the Control.Monad module, in the base package. Hence, you must import it in order to use it.
answered Nov 23 '18 at 18:16
AJFarmarAJFarmar
9,34722954
add a comment |
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You must import forever from Control.Monad. Add this to the top of your file:
import Control.Monad (forever)
When the compiler says variable not in scope..., it means "I don't know what this is supposed to be; you haven't defined it." This can be caused by not having the required modules imported.
How did I know this? If you search for forever on Hoogle, it says that it is in the Control.Monad module, in the base package. Hence, you must import it in order to use it.
answered Nov 23 '18 at 18:16
AJFarmarAJFarmar
9,34722954
add a comment |
You must import forever from Control.Monad. Add this to the top of your file:
import Control.Monad (forever)
When the compiler says variable not in scope..., it means "I don't know what this is supposed to be; you haven't defined it." This can be caused by not having the required modules imported.
How did I know this? If you search for forever on Hoogle, it says that it is in the Control.Monad module, in the base package. Hence, you must import it in order to use it.
answered Nov 23 '18 at 18:16
AJFarmarAJFarmar
9,34722954
add a comment |
You must import forever from Control.Monad. Add this to the top of your file:
import Control.Monad (forever)
When the compiler says variable not in scope..., it means "I don't know what this is supposed to be; you haven't defined it." This can be caused by not having the required modules imported.
How did I know this? If you search for forever on Hoogle, it says that it is in the Control.Monad module, in the base package. Hence, you must import it in order to use it.
answered Nov 23 '18 at 18:16
AJFarmarAJFarmar
9,34722954
You must import forever from Control.Monad. Add this to the top of your file:
import Control.Monad (forever)
When the compiler says variable not in scope..., it means "I don't know what this is supposed to be; you haven't defined it." This can be caused by not having the required modules imported.
How did I know this? If you search for forever on Hoogle, it says that it is in the Control.Monad module, in the base package. Hence, you must import it in order to use it.
answered Nov 23 '18 at 18:16
AJFarmarAJFarmar
9,34722954
answered Nov 23 '18 at 18:16
AJFarmarAJFarmar
9,34722954
answered Nov 23 '18 at 18:16
AJFarmarAJFarmar
9,34722954
answered Nov 23 '18 at 18:16
AJFarmarAJFarmar
9,34722954
9,34722954
add a comment |
add a comment |
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1
A side note:
foreveris not a monad, it is a function.– AJFarmar
Nov 23 '18 at 18:20
Your example has no variables, so we don't know why there's a variable out of scope. That just means you're referring to some variable that is unknown (in that context).
– Jorge Adriano
Nov 23 '18 at 18:59
1
Also while you can use
forever, if running something forever is confusing you this much, maybe you should be trying to do it without resorting toforeverfirst, for instructional purposes. All you need is to code an "infinite loop", i.e. write a function that "runs the code" then calls itself.– Jorge Adriano
Nov 23 '18 at 19:02