strings.rb in shen-ruby-0.4.0

- old
+ new

@@ -3,22 +3,27 @@
     # For the time being, Shen Ruby's string functions only support 8-bit 
     # characters. Once the Shen environment is up and running and passing
     # its test suite, strings will be extended to support UTF-8.
     module Strings
       def pos(s, n)
+        raise Kl::Error, "#{s} is not a string" unless s.kind_of? String
+        raise Kl::Error, "#{n} is not an integer" unless n.kind_of? Fixnum
+        if n < 0 || n >= s.length
+          raise Kl::Error, "out of bounds"
+        end
         s.byteslice(n)
       end
       
       def tlstr(s)
-        if s.empty?
-          :"shen-eos"
-        else
-          s.byteslice(1, s.bytesize - 1)
-        end
+        raise Kl::Error, "#{s} is not a string" unless s.kind_of? String
+        raise Kl::Error, "attempted to take tail of an empty string" if s.empty?
+        s.byteslice(1, s.bytesize - 1)
       end
       
       def cn(s1, s2)
+        raise Kl::Error, "#{s1} is not a string" unless s1.kind_of? String
+        raise Kl::Error, "#{s2} is not a string" unless s2.kind_of? String
         s1 + s2
       end
       
       def str(x)
         case x
@@ -42,13 +47,16 @@
       def string?(x)
         x.kind_of? String
       end
 
       define_method 'n->string' do |n|
+        raise Kl::Error, "#{n} is not an integer" unless n.kind_of? Fixnum
         "" << n
       end
 
       define_method 'string->n' do |s|
+        raise Kl::Error, "#{s} is not a string" unless s.kind_of? String
+        raise Kl::Error, 'attempted to get code point of empty string' if s.empty?
         s.bytes.to_a.first
       end
     end
   end
 end