Finish ruby interpreter

ports-rb/scheme.rb

@@ -32,14 +32,6 @@ def find(key)
         raise "Lookup error for #{key}"
       end
     end
-
-    def unset(key)
-      if @env.key?(key)
-        @env.delete(key)
-      else
-        raise "Cannot unset non-existent variable #{key}"
-      end
-    end
   end
 
   class Procedure
@@ -131,12 +123,6 @@ def expand(x, toplevel = false)
       var = x[1]
       require_syntax(x, var.is_a?(Symbol), "can set! only a symbol")
       [:set!, var, expand(x[2])]
-    when :unset
-      # (variable-unset! var)
-      require_syntax(x, x.length == 2)
-      var = x[1]
-      require_syntax(x, var.is_a?(Symbol), "can unset! only a symbol")
-      [:"variable-unset!", var]
     when :define, :"define-macro"
       # Check correct length
       require_syntax(x, x.length >= 3)
@@ -316,6 +302,14 @@ def evaluate(tokens, environment = GLOBAL_ENV)
           environment.find(var)[var] = evaluate(expression, environment)
           return
 
+        when :cond
+          branch = tokens[1..].find do |(test, expression)|
+            test == :else || evaluate(test, environment)
+          end
+          return if branch.nil?
+
+          tokens = branch[1]
+
         else
           expressions = tokens.map { |t| evaluate(t, environment) }
           procedure = expressions.shift

ports-rb/semantic-tests.rb

@@ -48,6 +48,10 @@ def matches(result, target)
 require_relative "scheme"
 
 # Run tests
+
+total = test_table.length
+failed = 0
+
 test_table.each do |entry|
   input = entry["input"]
 
@@ -61,5 +65,7 @@ def matches(result, target)
     puts "✅: #{input}"
   else
     puts "❌: #{input} got #{eval_result}[#{eval_result.class}] instead of #{entry["expected"]}[#{entry["expected"].class}]"
+    failed += 1
   end
 end
+puts "#{total} tests run, #{failed} failed"

ports/lispy-tests.json

@@ -4,6 +4,9 @@
     {"input": "(+ (* 2 100) (* 1 10))", "expected": 210},
     {"input": "(if (> 6 5) (+ 1 1) (+ 2 2))", "expected": 2},
     {"input": "(if (< 6 5) (+ 1 1) (+ 2 2))", "expected": 4},
+    {"input": "(cond ((< 6 5) 1) ((< 5 6) 2) (else 3) )", "expected": 2},
+    {"input": "(cond ((< 6 5) 1) (#f 2) (else 3) )", "expected": 3},
+    {"input": "(cond ((< 6 5) 1) (#f 2))", "expected": null},
     {"input": "(define x 3)", "expected": null},
     {"input": "x", "expected": 3}, 
     {"input": "(+ x x)", "expected": 6},