many edits, patch by Kelly Wilson!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44157 91177308-0d34-0410-b5e6-96231b3b80d8

docs/tutorial/LangImpl6.html

@@ -41,15 +41,16 @@ Variables / SSA Construction</li>
 
 <p>Welcome to Chapter 6 of the "<a href="index.html">Implementing a language
 with LLVM</a>" tutorial.  At this point in our tutorial, we now have a fully
-functional language that is fairly minimal, but also useful.  One big problem
-with it though is that it doesn't have many useful operators (like division,
-logical negation, or even any comparisons other than less-than.</p>
+functional language that is fairly minimal, but also useful.  There
+is still one big problem with it, however. Our language doesn't have many 
+useful operators (like division, logical negation, or even any comparisons 
+besides less-than).</p>
 
 <p>This chapter of the tutorial takes a wild digression into adding user-defined
-operators to the simple and beautiful Kaleidoscope language, giving us a 
-simple and ugly language in some ways, but also a powerful one at the same time.
+operators to the simple and beautiful Kaleidoscope language. This digression now gives 
+us a simple and ugly language in some ways, but also a powerful one at the same time.
 One of the great things about creating your own language is that you get to
-decide what is good or bad.  In this tutorial we'll assume that it is okay and
+decide what is good or bad.  In this tutorial we'll assume that it is okay to
 use this as a way to show some interesting parsing techniques.</p>
 
 <p>At the end of this tutorial, we'll run through an example Kaleidoscope 
@@ -73,8 +74,8 @@ capability to Kaleidoscope, which will let the user round out the set of
 operators that are supported.</p>
 
 <p>The point of going into user-defined operators in a tutorial like this is to
-show the power and flexibility of using a hand-written parser.  The parser we
-are using so far is using recursive descent for most parts of the grammar, and 
+show the power and flexibility of using a hand-written parser.  Thus far, the parser
+we have been implementing uses recursive descent for most parts of the grammar and 
 operator precedence parsing for the expressions.  See <a 
 href="LangImpl2.html">Chapter 2</a> for details.  Without using operator
 precedence parsing, it would be very difficult to allow the programmer to
@@ -152,12 +153,12 @@ static int gettok() {
 
 <p>This just adds lexer support for the unary and binary keywords, like we
 did in <a href="LangImpl5.html#iflexer">previous chapters</a>.  One nice thing
-about our current AST is that we represent binary operators fully generally
-with their ASCII code as the opcode.  For our extended operators, we'll use the
+about our current AST, is that we represent binary operators with full generalisation
+by using their ASCII code as the opcode.  For our extended operators, we'll use this
 same representation, so we don't need any new AST or parser support.</p>
 
 <p>On the other hand, we have to be able to represent the definitions of these
-new operators, in the "def binary| 5" part of the function definition.  In the
+new operators, in the "def binary| 5" part of the function definition.  In our
 grammar so far, the "name" for the function definition is parsed as the
 "prototype" production and into the <tt>PrototypeAST</tt> AST node.  To
 represent our new user-defined operators as prototypes, we have to extend
@@ -257,14 +258,14 @@ static PrototypeAST *ParsePrototype() {
 </pre>
 </div>
 
-<p>This is all fairly straight-forward parsing code, and we have already seen
-a lot of similar code in the past.  One interesting piece of this is the part
-that sets up <tt>FnName</tt> for binary operators.  This builds names like
-"binary@" for a newly defined "@" operator.  This takes advantage of the fact
-that symbol names in the LLVM symbol table are allowed to have any character in
-them, even including embedded nul characters.</p>
+<p>This is all fairly straightforward parsing code, and we have already seen
+a lot of similar code in the past.  One interesting part about the code above is 
+the couple lines that set up <tt>FnName</tt> for binary operators.  This builds names 
+like "binary@" for a newly defined "@" operator.  This then takes advantage of the 
+fact that symbol names in the LLVM symbol table are allowed to have any character in
+them, including embedded nul characters.</p>
 
-<p>The next interesting piece is codegen support for these binary operators.
+<p>The next interesting thing to add, is codegen support for these binary operators.
 Given our current structure, this is a simple addition of a default case for our
 existing binary operator node:</p>
 
@@ -301,10 +302,10 @@ Value *BinaryExprAST::Codegen() {
 <p>As you can see above, the new code is actually really simple.  It just does
 a lookup for the appropriate operator in the symbol table and generates a 
 function call to it.  Since user-defined operators are just built as normal
-functions (because the "prototype" boils down into a function with the right
+functions (because the "prototype" boils down to a function with the right
 name) everything falls into place.</p>
 
-<p>The final missing piece is a bit of top level magic, here:</p>
+<p>The final piece of code we are missing, is a bit of top level magic:</p>
 
 <div class="doc_code">
 <pre>
@@ -330,10 +331,9 @@ Function *FunctionAST::Codegen() {
 
 <p>Basically, before codegening a function, if it is a user-defined operator, we
 register it in the precedence table.  This allows the binary operator parsing
-logic we already have to handle it.  Since it is a fully-general operator
-precedence parser, this is all we need to do to "extend the grammar".</p>
+logic we already have in place to handle it.  Since we are working on a fully-general operator precedence parser, this is all we need to do to "extend the grammar".</p>
 
-<p>With that, we have useful user-defined binary operators.  This builds a lot
+<p>Now we have useful user-defined binary operators.  This builds a lot
 on the previous framework we built for other operators.  Adding unary operators
 is a bit more challenging, because we don't have any framework for it yet - lets
 see what it takes.</p>
@@ -347,7 +347,7 @@ see what it takes.</p>
 <div class="doc_text">
 
 <p>Since we don't currently support unary operators in the Kaleidoscope
-language, we'll need to add everything for them.  Above, we added simple
+language, we'll need to add everything to support them.  Above, we added simple
 support for the 'unary' keyword to the lexer.  In addition to that, we need an
 AST node:</p>
 
@@ -390,14 +390,14 @@ static ExprAST *ParseUnary() {
 </pre>
 </div>
 
-<p>The grammar we add is pretty straight-forward here.  If we see a unary
+<p>The grammar we add is pretty straightforward here.  If we see a unary
 operator when parsing a primary operator, we eat the operator as a prefix and
 parse the remaining piece as another unary operator.  This allows us to handle
 multiple unary operators (e.g. "!!x").  Note that unary operators can't have 
 ambiguous parses like binary operators can, so there is no need for precedence
 information.</p>
 
-<p>The problem with the above is that we need to call ParseUnary from somewhere.
+<p>The problem with this function, is that we need to call ParseUnary from somewhere.
 To do this, we change previous callers of ParsePrimary to call ParseUnary
 instead:</p>
 
@@ -424,7 +424,7 @@ static ExprAST *ParseExpression() {
 </pre>
 </div>
 
-<p>With these two simple changes, we now parse unary operators and build the
+<p>With these two simple changes, we are now able to parse unary operators and build the
 AST for them.  Next up, we need to add parser support for prototypes, to parse
 the unary operator prototype.  We extend the binary operator code above 
 with:</p>
@@ -587,7 +587,7 @@ Evaluated to 0.000000
 
 <p>Based on these simple primitive operations, we can start to define more
 interesting things.  For example, here's a little function that solves for the
-number of iterations it takes for a function in the complex plane to
+number of iterations it takes a function in the complex plane to
 converge:</p>
 
 <div class="doc_code">
@@ -779,8 +779,8 @@ and powerful language.  It may not be self-similar :), but it can be used to
 plot things that are!</p>
 
 <p>With this, we conclude the "adding user-defined operators" chapter of the
-tutorial.  We successfully extended our language with the ability to extend the
-language in the library, and showed how this can be used to build a simple but
+tutorial.  We have successfully augmented our language, adding the ability to extend the
+language in the library, and we have shown how this can be used to build a simple but
 interesting end-user application in Kaleidoscope.  At this point, Kaleidoscope
 can build a variety of applications that are functional and can call functions
 with side-effects, but it can't actually define and mutate a variable itself.
@@ -790,7 +790,7 @@ with side-effects, but it can't actually define and mutate a variable itself.
 languages, and it is not at all obvious how to <a href="LangImpl7.html">add
 support for mutable variables</a> without having to add an "SSA construction"
 phase to your front-end.  In the next chapter, we will describe how you can
-add this without building SSA in your front-end.</p>
+add variable mutation without building SSA in your front-end.</p>
 
 </div>