lib/lisp.rb in lisp-1.0.6 vs lib/lisp.rb in lisp-1.1.0

@@ -50,9 +50,15 @@
       lambda { |*args| execute(exp, scope.merge(Hash[params.zip(args)])) }
     when :if
       _, test, conseq, alt = exp
       exp = execute(test, scope) ? conseq : alt
       execute(exp, scope)
+    when :set!
+      _, var, exp = exp
+      if scope.has_key?(var) then scope[var] = execute(exp, scope) else raise "#{var} is undefined" end
+    when :begin
+      _, *exp = exp
+      exp.map { |exp| execute(exp) }.last
     else
       func, *args = exp.map { |exp| execute(exp, scope) }
       func.call(*args)
     end
   end