kddnewton · December 18, 2024 17:34 · Jun 10, 2022 · Jun 10, 2022 · Jun 10, 2022
diff --git a/json.rb b/json.rb
@@ -1,6 +1,6 @@
 require "json"
 
-struct = { a: 1, b: 2, c: [1, 2, 3], d: [{ e: 3 }, nil, false, true, [], {}] }
+struct = { "a" => 1, "b" => 2, "c" => [1, 2, 3], "d" => [{ "e" => 3 }, nil, false, true, [], {}] }
 source = JSON.dump(struct)
 
 tokens = []
@@ -22,9 +22,6 @@
 
 def parse_array(tokens)
   result = []
-  if tokens in [:"]", *rest]
-    return result, rest
-  end
 
   loop do
     item, tokens = parse_item(tokens)
@@ -39,9 +36,6 @@ def parse_array(tokens)
 
 def parse_object(tokens)
   result = {}
-  if tokens in [:"}", *rest]
-    return result, rest
-  end
 
   loop do
     tokens => [String => key, :":", *tokens]
@@ -57,10 +51,10 @@ def parse_object(tokens)
 
 def parse_item(tokens)
   case tokens
-  in [:"[", *rest]
-    parse_array(rest)
-  in [:"{", *rest]
-    parse_object(rest)
+  in [:"[", :"]", *rest] then [[], rest]
+  in [:"[", *rest]       then parse_array(rest)
+  in [:"{", :"}", *rest] then [{}, rest]
+  in [:"{", *rest]       then parse_object(rest)
   in [FalseClass | Integer | NilClass | String | TrueClass => value, *rest]
     [value, rest]
   end

diff --git a/json.rb b/json.rb
@@ -10,59 +10,66 @@
   tokens <<
     case source.strip
     when /\A[\{\}\[\],:]/ then $&.to_sym
-    when /\A(\d+)/ then $1.to_i
-    when /\A"([^"]*?)"/ then $1
-    when /\Anull/ then nil
-    when /\Atrue/ then true
-    when /\Afalse/ then false
-    else
-      raise
+    when /\A(\d+)/        then $1.to_i
+    when /\A"([^"]*?)"/   then $1
+    when /\A(true|false)/ then $1 == "true"
+    when /\Anull/         then nil
+    else                  raise
     end
 
   source = $'
 end
 
-def parse_item(tokens)
-  case tokens
-  in [:"{", *rest]
-    count = 1
-    index = rest.index { (count += { "{": 1, "}": -1 }.fetch(_1, 0)) == 0 }
-    [parse_object(rest[0...index]), rest[(index + 1)..]]
-  in [:"[", *rest]
-    count = 1
-    index = rest.index { (count += { "[": 1, "]": -1 }.fetch(_1, 0)) == 0 }
-    [parse_array(rest[0...index]), rest[(index + 1)..]]
-  in [value, *rest]
-    [value, rest]
+def parse_array(tokens)
+  result = []
+  if tokens in [:"]", *rest]
+    return result, rest
   end
-end
 
-def parse_object(tokens)
-  return {} if tokens in []
-  tokens => [String => key, :":", *rest]
+  loop do
+    item, tokens = parse_item(tokens)
+    result << item
 
-  case parse_item(rest)
-  in item, [:",", *rest] then { key => item }.merge(parse_object(rest))
-  in item, []            then { key => item }
+    case tokens
+    in [:"]", *rest] then return result, rest
+    in [:",", *rest] then tokens = rest
+    end
   end
 end
 
-def parse_array(tokens)
-  return [] if tokens in []
+def parse_object(tokens)
+  result = {}
+  if tokens in [:"}", *rest]
+    return result, rest
+  end
+
+  loop do
+    tokens => [String => key, :":", *tokens]
+    value, tokens = parse_item(tokens)
+    result[key] = value
 
-  case parse_item(tokens)
-  in item, [:",", *rest] then [item] + parse_array(rest)
-  in left, []            then [item]
+    case tokens
+    in [:"}", *rest] then return result, rest
+    in [:",", *rest] then tokens = rest
+    end
   end
 end
 
-def parse(tokens)
+def parse_item(tokens)
   case tokens
-  in [:"{", *rest, :"}"] then parse_object(rest)
-  in [:"[", *rest, :"]"] then parse_array(rest)
-  in [value]             then value
+  in [:"[", *rest]
+    parse_array(rest)
+  in [:"{", *rest]
+    parse_object(rest)
+  in [FalseClass | Integer | NilClass | String | TrueClass => value, *rest]
+    [value, rest]
   end
 end
 
+def parse(tokens)
+  parse_item(tokens) => [value, []]
+  value
+end
+
 p struct
 p parse(tokens)
diff --git a/json.rb b/json.rb
@@ -0,0 +1,68 @@
+require "json"
+
+struct = { a: 1, b: 2, c: [1, 2, 3], d: [{ e: 3 }, nil, false, true, [], {}] }
+source = JSON.dump(struct)
+
+tokens = []
+index = 0
+
+until source.empty?
+  tokens <<
+    case source.strip
+    when /\A[\{\}\[\],:]/ then $&.to_sym
+    when /\A(\d+)/ then $1.to_i
+    when /\A"([^"]*?)"/ then $1
+    when /\Anull/ then nil
+    when /\Atrue/ then true
+    when /\Afalse/ then false
+    else
+      raise
+    end
+
+  source = $'
+end
+
+def parse_item(tokens)
+  case tokens
+  in [:"{", *rest]
+    count = 1
+    index = rest.index { (count += { "{": 1, "}": -1 }.fetch(_1, 0)) == 0 }
+    [parse_object(rest[0...index]), rest[(index + 1)..]]
+  in [:"[", *rest]
+    count = 1
+    index = rest.index { (count += { "[": 1, "]": -1 }.fetch(_1, 0)) == 0 }
+    [parse_array(rest[0...index]), rest[(index + 1)..]]
+  in [value, *rest]
+    [value, rest]
+  end
+end
+
+def parse_object(tokens)
+  return {} if tokens in []
+  tokens => [String => key, :":", *rest]
+
+  case parse_item(rest)
+  in item, [:",", *rest] then { key => item }.merge(parse_object(rest))
+  in item, []            then { key => item }
+  end
+end
+
+def parse_array(tokens)
+  return [] if tokens in []
+
+  case parse_item(tokens)
+  in item, [:",", *rest] then [item] + parse_array(rest)
+  in left, []            then [item]
+  end
+end
+
+def parse(tokens)
+  case tokens
+  in [:"{", *rest, :"}"] then parse_object(rest)
+  in [:"[", *rest, :"]"] then parse_array(rest)
+  in [value]             then value
+  end
+end
+
+p struct
+p parse(tokens)