[NEW] do statement, d 10 a = a * a e

compiler.rb

@@ -26,13 +26,11 @@ class Compiler
     @vars = {}                   # symbol table
     @num_labels = 0              # used to generate unique labels
     @num_labels_with_suffix = Hash.new(0)
-    @num_conditions = 0
-    @break_stack = []            # for breaking out of loops
 
     # reserved words (... constant?)
     #
-    # if, else, end, while, until, repeat, break
-    @keywords = %w[i l e w u r b]
+    # if, else, end, while, until, repeat, for, do, break
+    @keywords = %w[i l e w u r f d b]
 
     # seed the lexer
     get_char
@@ -133,53 +131,48 @@ class Compiler
     x86_mov("dword [#{name}]", :eax)
   end
 
-  # Parse a statement.
-  def statement
-    case @look
-    when 'i'
-      if_else_stmt
-    when 'w'
-      while_stmt
-    when 'u'
-      until_stmt
-    when 'r'
-      repeat_stmt
-    when 'f'
-      for_stmt
-    when 'b'
-      break_stmt
-    else
-      assignment
-      newline
-    end
-  end
-
   # Parse a code block.
   def block(label=nil)
-    @break_stack.push(label) if label
     until @look == 'l' || @look == 'e' || eof?
-      statement
+      case @look
+      when 'i'
+        if_else_stmt(label)
+      when 'w'
+        while_stmt
+      when 'u'
+        until_stmt
+      when 'r'
+        repeat_stmt
+      when 'f'
+        for_stmt
+      when 'd'
+        do_stmt
+      when 'b'
+        break_stmt(label)
+      else
+        assignment
+        newline
+      end
       skip_any_whitespace
     end
-    @break_stack.pop if label
   end
   
   # Parse an if-else statement.
-  def if_else_stmt
+  def if_else_stmt(label)
     match('i')
     condition
     skip_any_whitespace
     else_label = unique_label(:end_or_else)
     end_label = else_label      # only generated if else clause present
     x86_jz(else_label)
-    block
+    block(label)
     if @look == 'l'
       match('l')
       skip_any_whitespace
       end_label = unique_label(:endif) # now we need the 2nd label
       x86_jmp(end_label)
       emit_label(else_label)
-      block
+      block(label)
     end
     match('e')
     emit_label(end_label)
@@ -257,19 +250,41 @@ class Compiler
     x86_add(:esp, 4)            # clean up the stack
   end
 
-  def break_stmt
+  # d 5
+  #   ...
+  # e
+  def do_stmt
+    match('d')
+    start_label = unique_label(:do)
+    end_label = unique_label(:enddo)
+    expression
+    skip_any_whitespace
+    x86_mov(:ecx, :eax)
+    x86_push(:ecx)
+    counter = '[esp]'
+    emit_label(start_label)
+    x86_mov(counter, :ecx)
+    block(end_label)
+    x86_mov(:ecx, counter)
+    match('e')
+    x86_loop(start_label)
+    x86_sub(:esp, 4)
+    emit_label(end_label)
+    x86_add(:esp, 4)
+  end
+
+  def break_stmt(label)
     match('b')
-    if @break_stack.empty?
+    if label
+      x86_jmp(label)
+    else
       expected(:'break to be somewhere useful',
-               :got => :'a break without a loop')
+               :got => :'a break outside a loop')
     end
-    x86_jmp(@break_stack.last)
   end
 
   # Evaluates any expression for now.  There are no boolean operators.
   def condition
-    # @num_conditions += 1
-    # emit("<condition ##{@num_conditions}>")
     expression
     x86_cmp(:eax, 0)            # 0 is false, anything else is true
     skip_whitespace
@@ -415,7 +430,7 @@ class Compiler
   end
 
 
-  # Get an identifier.
+  # Parse a name (identifier).
   def get_name
     expected(:identifier) unless alpha?(@look)
     name = many(method(:alnum?))
@@ -425,7 +440,7 @@ class Compiler
     name
   end
 
-  # Get a number.
+  # Parse a number.
   def get_num
     expected(:integer) unless digit?(@look)
     many(method(:digit?))
@@ -539,4 +554,8 @@ class Compiler
   def x86_cmp(a, b)
     emit("cmp #{a}, #{b}")
   end
+
+  def x86_loop(label)
+    emit("loop #{label}")
+  end
 end

test.code

@@ -3,28 +3,28 @@ aa=10
 somethinglong=65536
 x=5*(3-5)
 c=a-1
-d=-1
-g=x*2+2
-h=g-27/9
-j=h-8/2
-k=j-4*(5+5+5)
-m=k+85
+g=-1
+h=x*2+2
+j=h-27/9
+k=j-8/2
+m=k-4*(5+5+5)
+n=m+85
 
 i 1
-  d=3
+  x=3
   i 1 c=4
   e
 e
-i1d=3
+i1x=3
 i1c=4
 ee
 
 i 1
-  d=3
+  x=3
   i 1 c=4
   e
 l
- d=2
+ x=2
 e
 
 w 0
@@ -50,4 +50,8 @@ f x = 1 >> 5
   s = s + x
 e
 
+d 10
+  a = a * a
+e
+
 xitcode=a-a