Begin removing view related code and docs

demos/contractBasics.tri

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+!import "base" !Local
+!import "list" !Local
+!import "contracts" !Local
+
+-- A custom 'and' combinator written directly against base.matchResult.
+-- It succeeds only when *both* contracts succeed, threading the checked value
+-- from the first into the second. This makes the Result pair structure explicit.
+myAndC = (c1 c2 value rest :
+  matchResult
+    (msg _ : contractErr msg rest)
+    (v _ : c2 v rest)
+    (c1 value rest))
+
+-- Plain predicates lifted into contracts with a diagnostic message.
+natural? = guardC "natural" (n : gte? n 0)
+nonZero? = guardC "non-zero" (n : not? (isZero? n))
+
+-- Safe wrappers around partial base / list functions.
+-- The frontend desugars @ and =@ into runtime withContract applications.
+safeDiv a@natural? b@(myAndC natural? nonZero?) =@natural? div a b
+
+safeHead xs@(nonEmptyListOf anyC) =@anyC head xs
+safeTail xs@(nonEmptyListOf anyC) =@(listOf anyC) tail xs
+
+-- A higher-order wrapper: the supplied function must satisfy a contract,
+-- the input list must satisfy a contract, and the result list is guaranteed.
+checkedMap f@(fnContract anyC natural?) xs@(listOf anyC) =@(listOf natural?) map f xs
+
+-- Advertise the safe wrappers in the module manifest with their own contracts.
+!export safeDiv : fn2 natural? nonZero? natural?
+!export safeHead : fnContract (nonEmptyListOf anyC) anyC
+!export checkedMap : fn2 (fnContract anyC natural?) (listOf anyC) (listOf natural?)
+
+-- A small interaction-tree pipeline that uses contracts as recoverable effects.
+pipeline = (input :
+  do bindM
+    scaled <- checkM natural? (mul input 2)
+    half   <- handleM "contract"
+                  (_ : pureM 1)
+                  (checkM nonZero? (sub scaled 4))
+    pureM (div scaled half))
+
+main = runM (pipeline 5)