By using ‘:set’ Command we can change some of the default behaviors of the Haskell Environment.
Following are the commands to change settings.
Command | Description |
:set <option> ... | Set options |
:seti <option> ... | Set options for interactive evaluation only |
:set args <arg> ... | Set the arguments returned by System.getArgs |
:set prog <progname> | Set the value returned by System.getProgName |
Set the prompt used in GHCi | |
Set the continuation prompt used in GHCi | |
:set editor <cmd> | Set the command used for :edit |
Following are the various options used by both ‘:set’ ‘:unset’ commands.
Option | Description |
+m | Allow multiline commands |
+r | Revert top-level expressions after each evaluation |
+s | Print timing/memory stats after each evaluation |
+t | Print type after evaluation |
-<flags> | Most GHC command line flags can also be set here. (eg. -v2, -XFlexibleInstances, etc.) |
Change the GHCi prompt
By using ‘:set prompt promptName’ command, you can change the prompt name used in GHCi.
By using ‘:set prompt promptName’ command, you can change the prompt name used in GHCi.
Prelude> :set prompt ptr>
ptr>
ptr>let str1 = "Hello World"
ptr>putStrLn str1
Hello World
ptr>
By using various options of :set command, you can add extra information while displaying variables.
ptr>let str1 = "Hello World"
ptr>str1
"Hello World"
ptr>
ptr>:set +t +s
ptr>
ptr>str1
"Hello World"
it :: [Char]
(0.00 secs, 514,752 bytes)
ptr>
‘:set +t +s’ add type information of the variable, timing/memory stats of variable after every evaluation.
References
https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghci-set.html
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