Documentation tweaks and fixes

src/Util/Eff.md

@@ -22,9 +22,18 @@ import System.File
 Basic enumeration describing log levels, we define some (hidden) utility
 functions for working with these.
 
+The `Other n` log level is restricted to `n` greater than 4, to prevent
+ambiguity between custom log levels and predefined log levels.
+
 ```idris
 public export
-data Level = Err | Warn | Info | Debug | Trace | Other Nat 
+data Level : Type where
+  Err : Level
+  Warn : Level
+  Info : Level
+  Debug : Level
+  Trace : Level
+  Other : (n : Nat) -> {auto _ : n `GT` 4} -> Level
 ```
 
 <!-- idris
@@ -44,7 +53,7 @@ natToLevel 1 = Warn
 natToLevel 2 = Info
 natToLevel 3 = Debug
 natToLevel 4 = Trace
-natToLevel k = Other k
+natToLevel (S (S (S (S (S k))))) = Other (5 + k)
 
 export
 Eq Level where
@@ -130,10 +139,8 @@ handleLoggerIO max_level x =
     else pure . ignore $ x
 ```
 
-Use the `WriterL "log" String` effect like a logging library. We'll provide a
-few "log levels" as verbs for the effect, but no filtering is done, when logging
-is enabled, all logs are always displayed, however the log level is indicated
-with a colored tag.
+Provide a family of effectful actions that emit log messages at the different
+log levels.
 
 ```idris
 export
@@ -155,6 +162,10 @@ debug x = send $ Log Debug x
 export
 trace : Has Logger fs => Lazy String -> Eff fs ()
 trace x = send $ Log Trace x
+
+export
+logAt : Has Logger fs => Level -> Lazy String -> Eff fs ()
+logAt level x = send $ Log level x
 ```
 
 ## Choose