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| author | Erick Tryzelaar <idadesub@users.sourceforge.net> | 2008-03-31 08:44:50 +0000 |
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| committer | Erick Tryzelaar <idadesub@users.sourceforge.net> | 2008-03-31 08:44:50 +0000 |
| commit | 35295ffd500b39781e3ed015293e31c665a8b5bc (patch) | |
| tree | 6c4d914d54f96a7df264747a60381499cd4c35bb /docs/tutorial/OCamlLangImpl6.html | |
| parent | 9d15abe8385d17aa86c8144c8bbbac958fb91f17 (diff) | |
Chapter 5, 6, and 7 of the ocaml/kaleidoscope tutorial
and fix some tabs in chapter 3 and 4.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48978 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/tutorial/OCamlLangImpl6.html')
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diff --git a/docs/tutorial/OCamlLangImpl6.html b/docs/tutorial/OCamlLangImpl6.html new file mode 100644 index 0000000000..780cab8191 --- /dev/null +++ b/docs/tutorial/OCamlLangImpl6.html @@ -0,0 +1,1569 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" + "http://www.w3.org/TR/html4/strict.dtd"> + +<html> +<head> + <title>Kaleidoscope: Extending the Language: User-defined Operators</title> + <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> + <meta name="author" content="Chris Lattner"> + <meta name="author" content="Erick Tryzelaar"> + <link rel="stylesheet" href="../llvm.css" type="text/css"> +</head> + +<body> + +<div class="doc_title">Kaleidoscope: Extending the Language: User-defined Operators</div> + +<ul> +<li><a href="index.html">Up to Tutorial Index</a></li> +<li>Chapter 6 + <ol> + <li><a href="#intro">Chapter 6 Introduction</a></li> + <li><a href="#idea">User-defined Operators: the Idea</a></li> + <li><a href="#binary">User-defined Binary Operators</a></li> + <li><a href="#unary">User-defined Unary Operators</a></li> + <li><a href="#example">Kicking the Tires</a></li> + <li><a href="#code">Full Code Listing</a></li> + </ol> +</li> +<li><a href="OCamlLangImpl7.html">Chapter 7</a>: Extending the Language: Mutable +Variables / SSA Construction</li> +</ul> + +<div class="doc_author"> + <p> + Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a> + and <a href="mailto:idadesub@users.sourceforge.net">Erick Tryzelaar</a> + </p> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"><a name="intro">Chapter 6 Introduction</a></div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<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. 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. 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 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 +application that <a href="#example">renders the Mandelbrot set</a>. This gives +an example of what you can build with Kaleidoscope and its feature set.</p> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"><a name="idea">User-defined Operators: the Idea</a></div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p> +The "operator overloading" that we will add to Kaleidoscope is more general than +languages like C++. In C++, you are only allowed to redefine existing +operators: you can't programatically change the grammar, introduce new +operators, change precedence levels, etc. In this chapter, we will add this +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. 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="OCamlLangImpl2.html">Chapter 2</a> for details. Without using operator +precedence parsing, it would be very difficult to allow the programmer to +introduce new operators into the grammar: the grammar is dynamically extensible +as the JIT runs.</p> + +<p>The two specific features we'll add are programmable unary operators (right +now, Kaleidoscope has no unary operators at all) as well as binary operators. +An example of this is:</p> + +<div class="doc_code"> +<pre> +# Logical unary not. +def unary!(v) + if v then + 0 + else + 1; + +# Define > with the same precedence as <. +def binary> 10 (LHS RHS) + RHS < LHS; + +# Binary "logical or", (note that it does not "short circuit") +def binary| 5 (LHS RHS) + if LHS then + 1 + else if RHS then + 1 + else + 0; + +# Define = with slightly lower precedence than relationals. +def binary= 9 (LHS RHS) + !(LHS < RHS | LHS > RHS); +</pre> +</div> + +<p>Many languages aspire to being able to implement their standard runtime +library in the language itself. In Kaleidoscope, we can implement significant +parts of the language in the library!</p> + +<p>We will break down implementation of these features into two parts: +implementing support for user-defined binary operators and adding unary +operators.</p> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"><a name="binary">User-defined Binary Operators</a></div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>Adding support for user-defined binary operators is pretty simple with our +current framework. We'll first add support for the unary/binary keywords:</p> + +<div class="doc_code"> +<pre> +type token = + ... + <b>(* operators *) + | Binary | Unary</b> + +... + +and lex_ident buffer = parser + ... + | "for" -> [< 'Token.For; stream >] + | "in" -> [< 'Token.In; stream >] + <b>| "binary" -> [< 'Token.Binary; stream >] + | "unary" -> [< 'Token.Unary; stream >]</b> +</pre> +</div> + +<p>This just adds lexer support for the unary and binary keywords, like we +did in <a href="OCamlLangImpl5.html#iflexer">previous chapters</a>. One nice +thing 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 our +grammar so far, the "name" for the function definition is parsed as the +"prototype" production and into the <tt>Ast.Prototype</tt> AST node. To +represent our new user-defined operators as prototypes, we have to extend +the <tt>Ast.Prototype</tt> AST node like this:</p> + +<div class="doc_code"> +<pre> +(* proto - This type represents the "prototype" for a function, which captures + * its name, and its argument names (thus implicitly the number of arguments the + * function takes). *) +type proto = + | Prototype of string * string array + <b>| BinOpPrototype of string * string array * int</b> +</pre> +</div> + +<p>Basically, in addition to knowing a name for the prototype, we now keep track +of whether it was an operator, and if it was, what precedence level the operator +is at. The precedence is only used for binary operators (as you'll see below, +it just doesn't apply for unary operators). Now that we have a way to represent +the prototype for a user-defined operator, we need to parse it:</p> + +<div class="doc_code"> +<pre> +(* prototype + * ::= id '(' id* ')' + <b>* ::= binary LETTER number? (id, id) + * ::= unary LETTER number? (id) *)</b> +let parse_prototype = + let rec parse_args accumulator = parser + | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e + | [< >] -> accumulator + in + let parse_operator = parser + | [< 'Token.Unary >] -> "unary", 1 + | [< 'Token.Binary >] -> "binary", 2 + in + let parse_binary_precedence = parser + | [< 'Token.Number n >] -> int_of_float n + | [< >] -> 30 + in + parser + | [< 'Token.Ident id; + 'Token.Kwd '(' ?? "expected '(' in prototype"; + args=parse_args []; + 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> + (* success. *) + Ast.Prototype (id, Array.of_list (List.rev args)) + <b>| [< (prefix, kind)=parse_operator; + 'Token.Kwd op ?? "expected an operator"; + (* Read the precedence if present. *) + binary_precedence=parse_binary_precedence; + 'Token.Kwd '(' ?? "expected '(' in prototype"; + args=parse_args []; + 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> + let name = prefix ^ (String.make 1 op) in + let args = Array.of_list (List.rev args) in + + (* Verify right number of arguments for operator. *) + if Array.length args != kind + then raise (Stream.Error "invalid number of operands for operator") + else + if kind == 1 then + Ast.Prototype (name, args) + else + Ast.BinOpPrototype (name, args, binary_precedence)</b> + | [< >] -> + raise (Stream.Error "expected function name in prototype") +</pre> +</div> + +<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>name</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 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> + +<div class="doc_code"> +<pre> +let codegen_expr = function + ... + | Ast.Binary (op, lhs, rhs) -> + let lhs_val = codegen_expr lhs in + let rhs_val = codegen_expr rhs in + begin + match op with + | '+' -> build_add lhs_val rhs_val "addtmp" builder + | '-' -> build_sub lhs_val rhs_val "subtmp" builder + | '*' -> build_mul lhs_val rhs_val "multmp" builder + | '<' -> + (* Convert bool 0/1 to double 0.0 or 1.0 *) + let i = build_fcmp Fcmp.Ult lhs_val rhs_val "cmptmp" builder in + build_uitofp i double_type "booltmp" builder + <b>| _ -> + (* If it wasn't a builtin binary operator, it must be a user defined + * one. Emit a call to it. *) + let callee = "binary" ^ (String.make 1 op) in + let callee = + match lookup_function callee the_module with + | Some callee -> callee + | None -> raise (Error "binary operator not found!") + in + build_call callee [|lhs_val; rhs_val|] "binop" builder</b> + end +</pre> +</div> + +<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 to a function with the right +name) everything falls into place.</p> + +<p>The final piece of code we are missing, is a bit of top level magic:</p> + +<div class="doc_code"> +<pre> +let codegen_func the_fpm = function + | Ast.Function (proto, body) -> + Hashtbl.clear named_values; + let the_function = codegen_proto proto in + + <b>(* If this is an operator, install it. *) + begin match proto with + | Ast.BinOpPrototype (name, args, prec) -> + let op = name.[String.length name - 1] in + Hashtbl.add Parser.binop_precedence op prec; + | _ -> () + end;</b> + + (* Create a new basic block to start insertion into. *) + let bb = append_block "entry" the_function in + position_at_end bb builder; + ... +</pre> +</div> + +<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 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>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> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"><a name="unary">User-defined Unary Operators</a></div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>Since we don't currently support unary operators in the Kaleidoscope +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> + +<div class="doc_code"> +<pre> +type expr = + ... + (* variant for a unary operator. *) + | Unary of char * expr + ... +</pre> +</div> + +<p>This AST node is very simple and obvious by now. It directly mirrors the +binary operator AST node, except that it only has one child. With this, we +need to add the parsing logic. Parsing a unary operator is pretty simple: we'll +add a new function to do it:</p> + +<div class="doc_code"> +<pre> +(* unary + * ::= primary + * ::= '!' unary *) +and parse_unary = parser + (* If this is a unary operator, read it. *) + | [< 'Token.Kwd op when op != '(' && op != ')'; operand=parse_expr >] -> + Ast.Unary (op, operand) + + (* If the current token is not an operator, it must be a primary expr. *) + | [< stream >] -> parse_primary stream +</pre> +</div> + +<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 this function, is that we need to call ParseUnary from +somewhere. To do this, we change previous callers of ParsePrimary to call +<tt>parse_unary</tt> instead:</p> + +<div class="doc_code"> +<pre> +(* binoprhs + * ::= ('+' primary)* *) +and parse_bin_rhs expr_prec lhs stream = + ... + <b>(* Parse the unary expression after the binary operator. *) + let rhs = parse_unary stream in</b> + ... + +... + +(* expression + * ::= primary binoprhs *) +and parse_expr = parser + | [< lhs=<b>parse_unary</b>; stream >] -> parse_bin_rhs 0 lhs stream +</pre> +</div> + +<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> + +<div class="doc_code"> +<pre> +(* prototype + * ::= id '(' id* ')' + * ::= binary LETTER number? (id, id) + <b>* ::= unary LETTER number? (id)</b> *) +let parse_prototype = + let rec parse_args accumulator = parser + | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e + | [< >] -> accumulator + in + <b>let parse_operator = parser + | [< 'Token.Unary >] -> "unary", 1 + | [< 'Token.Binary >] -> "binary", 2 + in</b> + let parse_binary_precedence = parser + | [< 'Token.Number n >] -> int_of_float n + | [< >] -> 30 + in + parser + | [< 'Token.Ident id; + 'Token.Kwd '(' ?? "expected '(' in prototype"; + args=parse_args []; + 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> + (* success. *) + Ast.Prototype (id, Array.of_list (List.rev args)) + <b>| [< (prefix, kind)=parse_operator; + 'Token.Kwd op ?? "expected an operator"; + (* Read the precedence if present. *) + binary_precedence=parse_binary_precedence; + 'Token.Kwd '(' ?? "expected '(' in prototype"; + args=parse_args []; + 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> + let name = prefix ^ (String.make 1 op) in + let args = Array.of_list (List.rev args) in + + (* Verify right number of arguments for operator. *) + if Array.length args != kind + then raise (Stream.Error "invalid number of operands for operator") + else + if kind == 1 then + Ast.Prototype (name, args) + else + Ast.BinOpPrototype (name, args, binary_precedence)</b> + | [< >] -> + raise (Stream.Error "expected function name in prototype") +</pre> +</div> + +<p>As with binary operators, we name unary operators with a name that includes +the operator character. This assists us at code generation time. Speaking of, +the final piece we need to add is codegen support for unary operators. It looks +like this:</p> + +<div class="doc_code"> +<pre> +let rec codegen_expr = function + ... + | Ast.Unary (op, operand) -> + let operand = codegen_expr operand in + let callee = "unary" ^ (String.make 1 op) in + let callee = + match lookup_function callee the_module with + | Some callee -> callee + | None -> raise (Error "unknown unary operator") + in + build_call callee [|operand|] "unop" builder +</pre> +</div> + +<p>This code is similar to, but simpler than, the code for binary operators. It +is simpler primarily because it doesn't need to handle any predefined operators. +</p> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"><a name="example">Kicking the Tires</a></div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>It is somewhat hard to believe, but with a few simple extensions we've +covered in the last chapters, we have grown a real-ish language. With this, we +can do a lot of interesting things, including I/O, math, and a bunch of other +things. For example, we can now add a nice sequencing operator (printd is +defined to print out the specified value and a newline):</p> + +<div class="doc_code"> +<pre> +ready> <b>extern printd(x);</b> +Read extern: declare double @printd(double) +ready> <b>def binary : 1 (x y) 0; # Low-precedence operator that ignores operands.</b> +.. +ready> <b>printd(123) : printd(456) : printd(789);</b> +123.000000 +456.000000 +789.000000 +Evaluated to 0.000000 +</pre> +</div> + +<p>We can also define a bunch of other "primitive" operations, such as:</p> + +<div class="doc_code"> +<pre> +# Logical unary not. +def unary!(v) + if v then + 0 + else + 1; + +# Unary negate. +def unary-(v) + 0-v; + +# Define > with the same precedence as >. +def binary> 10 (LHS RHS) + RHS < LHS; + +# Binary logical or, which does not short circuit. +def binary| 5 (LHS RHS) + if LHS then + 1 + else if RHS then + 1 + else + 0; + +# Binary logical and, which does not short circuit. +def binary& 6 (LHS RHS) + if !LHS then + 0 + else + !!RHS; + +# Define = with slightly lower precedence than relationals. +def binary = 9 (LHS RHS) + !(LHS < RHS | LHS > RHS); + +</pre> +</div> + + +<p>Given the previous if/then/else support, we can also define interesting +functions for I/O. For example, the following prints out a character whose +"density" reflects the value passed in: the lower the value, the denser the +character:</p> + +<div class="doc_code"> +<pre> +ready> +<b> +extern putchard(char) +def printdensity(d) + if d > 8 then + putchard(32) # ' ' + else if d > 4 then + putchard(46) # '.' + else if d > 2 then + putchard(43) # '+' + else + putchard(42); # '*'</b> +... +ready> <b>printdensity(1): printdensity(2): printdensity(3) : + printdensity(4): printdensity(5): printdensity(9): putchard(10);</b> +*++.. +Evaluated to 0.000000 +</pre> +</div> + +<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 a function in the complex plane to +converge:</p> + +<div class="doc_code"> +<pre> +# determine whether the specific location diverges. +# Solve for z = z^2 + c in the complex plane. +def mandleconverger(real imag iters creal cimag) + if iters > 255 | (real*real + imag*imag > 4) then + iters + else + mandleconverger(real*real - imag*imag + creal, + 2*real*imag + cimag, + iters+1, creal, cimag); + +# return the number of iterations required for the iteration to escape +def mandleconverge(real imag) + mandleconverger(real, imag, 0, real, imag); +</pre> +</div> + +<p>This "z = z<sup>2</sup> + c" function is a beautiful little creature that is the basis +for computation of the <a +href="http://en.wikipedia.org/wiki/Mandelbrot_set">Mandelbrot Set</a>. Our +<tt>mandelconverge</tt> function returns the number of iterations that it takes +for a complex orbit to escape, saturating to 255. This is not a very useful +function by itself, but if you plot its value over a two-dimensional plane, +you can see the Mandelbrot set. Given that we are limited to using putchard +here, our amazing graphical output is limited, but we can whip together +something using the density plotter above:</p> + +<div class="doc_code"> +<pre> +# compute and plot the mandlebrot set with the specified 2 dimensional range +# info. +def mandelhelp(xmin xmax xstep ymin ymax ystep) + for y = ymin, y < ymax, ystep in ( + (for x = xmin, x < xmax, xstep in + printdensity(mandleconverge(x,y))) + : putchard(10) + ) + +# mandel - This is a convenient helper function for ploting the mandelbrot set +# from the specified position with the specified Magnification. +def mandel(realstart imagstart realmag imagmag) + mandelhelp(realstart, realstart+realmag*78, realmag, + imagstart, imagstart+imagmag*40, imagmag); +</pre> +</div> + +<p>Given this, we can try plotting out the mandlebrot set! Lets try it out:</p> + +<div class="doc_code"> +<pre> +ready> <b>mandel(-2.3, -1.3, 0.05, 0.07);</b> +*******************************+++++++++++************************************* +*************************+++++++++++++++++++++++******************************* +**********************+++++++++++++++++++++++++++++**************************** +*******************+++++++++++++++++++++.. ...++++++++************************* +*****************++++++++++++++++++++++.... ...+++++++++*********************** +***************+++++++++++++++++++++++..... ...+++++++++********************* +**************+++++++++++++++++++++++.... ....+++++++++******************** +*************++++++++++++++++++++++...... .....++++++++******************* +************+++++++++++++++++++++....... .......+++++++****************** +***********+++++++++++++++++++.... ... .+++++++***************** +**********+++++++++++++++++....... .+++++++**************** +*********++++++++++++++........... ...+++++++*************** +********++++++++++++............ ...++++++++************** +********++++++++++... .......... .++++++++************** +*******+++++++++..... .+++++++++************* +*******++++++++...... ..+++++++++************* +*******++++++....... ..+++++++++************* +*******+++++...... ..+++++++++************* +*******.... .... ...+++++++++************* +*******.... . ...+++++++++************* +*******+++++...... ...+++++++++************* +*******++++++....... ..+++++++++************* +*******++++++++...... .+++++++++************* +*******+++++++++..... ..+++++++++************* +********++++++++++... .......... .++++++++************** +********++++++++++++............ ...++++++++************** +*********++++++++++++++.......... ...+++++++*************** +**********++++++++++++++++........ .+++++++**************** +**********++++++++++++++++++++.... ... ..+++++++**************** +***********++++++++++++++++++++++....... .......++++++++***************** +************+++++++++++++++++++++++...... ......++++++++****************** +**************+++++++++++++++++++++++.... ....++++++++******************** +***************+++++++++++++++++++++++..... ...+++++++++********************* +*****************++++++++++++++++++++++.... ...++++++++*********************** +*******************+++++++++++++++++++++......++++++++************************* +*********************++++++++++++++++++++++.++++++++*************************** +*************************+++++++++++++++++++++++******************************* +******************************+++++++++++++************************************ +******************************************************************************* +******************************************************************************* +******************************************************************************* +Evaluated to 0.000000 +ready> <b>mandel(-2, -1, 0.02, 0.04);</b> +**************************+++++++++++++++++++++++++++++++++++++++++++++++++++++ +***********************++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +*********************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++. +*******************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++... +*****************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++..... +***************++++++++++++++++++++++++++++++++++++++++++++++++++++++++........ +**************++++++++++++++++++++++++++++++++++++++++++++++++++++++........... +************+++++++++++++++++++++++++++++++++++++++++++++++++++++.............. +***********++++++++++++++++++++++++++++++++++++++++++++++++++........ . +**********++++++++++++++++++++++++++++++++++++++++++++++............. +********+++++++++++++++++++++++++++++++++++++++++++.................. +*******+++++++++++++++++++++++++++++++++++++++....................... +******+++++++++++++++++++++++++++++++++++........................... +*****++++++++++++++++++++++++++++++++............................ +*****++++++++++++++++++++++++++++............................... +****++++++++++++++++++++++++++...... ......................... +***++++++++++++++++++++++++......... ...... ........... +***++++++++++++++++++++++............ +**+++++++++++++++++++++.............. +**+++++++++++++++++++................ +*++++++++++++++++++................. +*++++++++++++++++............ ... +*++++++++++++++.............. +*+++....++++................ +*.......... ........... +* +*.......... ........... +*+++....++++................ +*++++++++++++++.............. +*++++++++++++++++............ ... +*++++++++++++++++++................. +**+++++++++++++++++++................ +**+++++++++++++++++++++.............. +***++++++++++++++++++++++............ +***++++++++++++++++++++++++......... ...... ........... +****++++++++++++++++++++++++++...... ......................... +*****++++++++++++++++++++++++++++............................... +*****++++++++++++++++++++++++++++++++............................ +******+++++++++++++++++++++++++++++++++++........................... +*******+++++++++++++++++++++++++++++++++++++++....................... +********+++++++++++++++++++++++++++++++++++++++++++.................. +Evaluated to 0.000000 +ready> <b>mandel(-0.9, -1.4, 0.02, 0.03);</b> +******************************************************************************* +******************************************************************************* +******************************************************************************* +**********+++++++++++++++++++++************************************************ +*+++++++++++++++++++++++++++++++++++++++*************************************** ++++++++++++++++++++++++++++++++++++++++++++++********************************** +++++++++++++++++++++++++++++++++++++++++++++++++++***************************** +++++++++++++++++++++++++++++++++++++++++++++++++++++++************************* ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++********************** ++++++++++++++++++++++++++++++++++.........++++++++++++++++++******************* ++++++++++++++++++++++++++++++++.... ......+++++++++++++++++++**************** ++++++++++++++++++++++++++++++....... ........+++++++++++++++++++************** +++++++++++++++++++++++++++++........ ........++++++++++++++++++++************ ++++++++++++++++++++++++++++......... .. ...+++++++++++++++++++++********** +++++++++++++++++++++++++++........... ....++++++++++++++++++++++******** +++++++++++++++++++++++++............. .......++++++++++++++++++++++****** ++++++++++++++++++++++++............. ........+++++++++++++++++++++++**** +++++++++++++++++++++++........... ..........++++++++++++++++++++++*** +++++++++++++++++++++........... .........++++++++++++++++++++++* +++++++++++++++++++............ ...........++++++++++++++++++++ +++++++++++++++++............... .............++++++++++++++++++ +++++++++++++++................. ...............++++++++++++++++ +++++++++++++.................. .................++++++++++++++ ++++++++++.................. .................+++++++++++++ +++++++........ . ......... ..++++++++++++ +++............ ...... ....++++++++++ +.............. ...++++++++++ +.............. ....+++++++++ +.............. .....++++++++ +............. ......++++++++ +........... .......++++++++ +......... ........+++++++ +......... ........+++++++ +......... ....+++++++ +........ ...+++++++ +....... ...+++++++ + ....+++++++ + .....+++++++ + ....+++++++ + ....+++++++ + ....+++++++ +Evaluated to 0.000000 +ready> <b>^D</b> +</pre> +</div> + +<p>At this point, you may be starting to realize that Kaleidoscope is a real +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 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.</p> + +<p>Strikingly, variable mutation is an important feature of some +languages, and it is not at all obvious how to <a href="OCamlLangImpl7.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 variable mutation without building SSA in your front-end.</p> + +</div> + + +<!-- *********************************************************************** --> +<div class="doc_section"><a name="code">Full Code Listing</a></div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p> +Here is the complete code listing for our running example, enhanced with the +if/then/else and for expressions.. To build this example, use: +</p> + +<div class="doc_code"> +<pre> +# Compile +ocamlbuild toy.byte +# Run +./toy.byte +</pre> +</div> + +<p>Here is the code:</p> + +<dl> +<dt>_tags:</dt> +<dd class="doc_code"> +<pre> +<{lexer,parser}.ml>: use_camlp4, pp(camlp4of) +<*.{byte,native}>: g++, use_llvm, use_llvm_analysis +<*.{byte,native}>: use_llvm_executionengine, use_llvm_target +<*.{byte,native}>: use_llvm_scalar_opts, use_bindings +</pre> +</dd> + +<dt>myocamlbuild.ml:</dt> +<dd class="doc_code"> +<pre> +open Ocamlbuild_plugin;; + +ocaml_lib ~extern:true "llvm";; +ocaml_lib ~extern:true "llvm_analysis";; +ocaml_lib ~extern:true "llvm_executionengine";; +ocaml_lib ~extern:true "llvm_target";; +ocaml_lib ~extern:true "llvm_scalar_opts";; + +flag ["link"; "ocaml"; "g++"] (S[A"-cc"; A"g++"]);; +dep ["link"; "ocaml"; "use_bindings"] ["bindings.o"];; +</pre> +</dd> + +<dt>token.ml:</dt> +<dd class="doc_code"> +<pre> +(*===----------------------------------------------------------------------=== + * Lexer Tokens + *===----------------------------------------------------------------------===*) + +(* The lexer returns these 'Kwd' if it is an unknown character, otherwise one of + * these others for known things. *) +type token = + (* commands *) + | Def | Extern + + (* primary *) + | Ident of string | Number of float + + (* unknown *) + | Kwd of char + + (* control *) + | If | Then | Else + | For | In + + (* operators *) + | Binary | Unary +</pre> +</dd> + +<dt>lexer.ml:</dt> +<dd class="doc_code"> +<pre> +(*===----------------------------------------------------------------------=== + * Lexer + *===----------------------------------------------------------------------===*) + +let rec lex = parser + (* Skip any whitespace. *) + | [< ' (' ' | '\n' | '\r' | '\t'); stream >] -> lex stream + + (* identifier: [a-zA-Z][a-zA-Z0-9] *) + | [< ' ('A' .. 'Z' | 'a' .. 'z' as c); s |