Add logger

Author: TimWhiting

std/core-extras.kk

@@ -16,6 +16,11 @@ extern import
 pub fun pretend-not-reachable(?kk-file-line: string): b
   impossible()
 
+pub fun no-effect-top(a: () -> pure a, ?kk-file-line: string): a
+  with pretend-no-div
+  catch(a) fn(err)
+    impossible(err.show)
+
 pub fun list/and(l: list<bool>): bool
   match l
     Nil -> True

std/log.kk

@@ -0,0 +1,11 @@
+import std/data/linearmap
+
+linear effect log
+  fun log(name: string, message: string): ()
+
+fun with-logs(action: () -> <log|e> ()): e ()
+  var logs := LinearMap([])
+  with handler
+    fun log(name, message)
+      logs := logs.set(name, logs.lookup(name).default("") ++ message ++ "\n")
+  action()