M core/scope.nim → core/scope.nim

@@ -41,11 +41,11 @@ scope.symbols.excl(key)
     return true
   return false
 
-proc setSymbol*(scope: ref MinScope, key: string, value: MinOperator): bool {.discardable.}=
+proc setSymbol*(scope: ref MinScope, key: string, value: MinOperator, override = false): bool {.discardable.}=
   result = false
   # check if a symbol already exists in current scope
   if not scope.isNil and scope.symbols.hasKey(key):
-    if scope.symbols[key].sealed:
+    if not override and scope.symbols[key].sealed:
       raiseInvalid("Symbol '$1' is sealed." % key) 
     scope.symbols[key] = value
     result = true

M lib/min_lang.nim → lib/min_lang.nim

@@ -745,6 +745,13 @@ var s = i.scope.getSymbol(sym.getString)
       s.sealed = true
       i.scope.setSymbol(sym.getString, s)
 
+    .symbol("unseal") do (i: In):
+      var sym: MinValue 
+      i.reqStringLike sym
+      var s = i.scope.getSymbol(sym.getString) 
+      s.sealed = false
+      i.scope.setSymbol(sym.getString, s, true)
+
     .symbol("quote-bind") do (i: In):
       var s, m: MinValue
       i.reqString(s)

M tests/lang.min → tests/lang.min

@@ -130,6 +130,13 @@ 
   (((2 :a1 'a1 seal 3 :a1) ("failed")) try "failed" ==) assert
 
   (
+    1 :a1
+    'a1 seal
+    'a1 unseal
+    2 :a1
+    2 a1 ==) assert
+
+  (
    (
     (((error "TestError")(message "Test Message")) raise) 
     ('error dget)