proc.c

/*
 * MacRuby implementation of Ruby 1.9's proc.c.
 *
 * This file is covered by the Ruby license. See COPYING for more details.
 *
 * Copyright (C) 2012, The MacRuby Team. All rights reserved.
 * Copyright (C) 2007-2011, Apple Inc. All rights reserved.
 * Copyright (C) 2004-2007 Koichi Sasada
 */

#include "macruby_internal.h"
#include "ruby/node.h"
#include "vm.h"
#include "class.h"

#define GetCoreDataFromValue(obj, type, ptr) do { \
    ptr = (type*)DATA_PTR(obj); \
} while (0)

#define GetProcPtr(obj, ptr) GetCoreDataFromValue(obj, rb_vm_block_t, ptr)

#define GetBindingPtr(obj, ptr) \
    GetCoreDataFromValue((obj), rb_vm_binding_t, (ptr))

VALUE rb_cUnboundMethod;
VALUE rb_cMethod;
VALUE rb_cBinding;
VALUE rb_cProc;

/* Proc */

VALUE
rb_proc_alloc(VALUE klass)
{
    VALUE obj;
    rb_vm_block_t *proc;
    obj = Data_Make_Struct(klass, rb_vm_block_t, NULL, NULL, proc);
    MEMZERO(proc, rb_vm_block_t, 1);
    return obj;
}

VALUE
rb_proc_alloc_with_block(VALUE klass, rb_vm_block_t *proc)
{
    if (proc->proc != Qnil) {
	return proc->proc;
    }

    VALUE obj;
    obj = Data_Wrap_Struct(klass, NULL, NULL, proc);
    proc->proc = obj; // weak
    rb_vm_block_make_detachable_proc(proc);
    return obj;
}

VALUE
rb_obj_is_proc(VALUE obj)
{
    if (CLASS_OF(obj) == rb_cProc) {
	return Qtrue;
    }
    else {
	return Qfalse;
    }
}

static inline bool
rb_obj_is_method(VALUE obj)
{
    VALUE klass = CLASS_OF(obj);
    return (klass == rb_cMethod) || (klass == rb_cUnboundMethod);
}

static VALUE
proc_dup(VALUE self, SEL sel)
{
    rb_vm_block_t *src;
    GetProcPtr(self, src);
    return Data_Wrap_Struct(CLASS_OF(self), NULL, NULL, src);
}

static VALUE
proc_clone(VALUE self, SEL sel)
{
    VALUE procval = proc_dup(self, 0);
    CLONESETUP(procval, self);
    return procval;
}

/*
 * call-seq:
 *   prc.lambda? => true or false
 *
 * Returns true for a Proc object which argument handling is rigid.
 * Such procs are typically generated by lambda.
 *
 * A Proc object generated by proc ignore extra arguments.
 *
 *   proc {|a,b| [a,b] }.call(1,2,3)    => [1,2]
 *
 * It provides nil for lacked arguments.
 *
 *   proc {|a,b| [a,b] }.call(1)        => [1,nil]
 *
 * It expand single-array argument.
 *
 *   proc {|a,b| [a,b] }.call([1,2])    => [1,2]
 *
 * A Proc object generated by lambda doesn't have such tricks.
 *
 *   lambda {|a,b| [a,b] }.call(1,2,3)  => ArgumentError
 *   lambda {|a,b| [a,b] }.call(1)      => ArgumentError
 *   lambda {|a,b| [a,b] }.call([1,2])  => ArgumentError
 *
 * Proc#lambda? is a predicate for the tricks.
 * It returns true if no tricks.
 *
 *   lambda {}.lambda?          => true
 *   proc {}.lambda?            => false
 *
 * Proc.new is same as proc.
 *
 *   Proc.new {}.lambda?        => false
 *
 * lambda, proc and Proc.new preserves the tricks of
 * a Proc object given by & argument.
 *
 *   lambda(&lambda {}).lambda?   => true
 *   proc(&lambda {}).lambda?     => true
 *   Proc.new(&lambda {}).lambda? => true
 *
 *   lambda(&proc {}).lambda?   => false
 *   proc(&proc {}).lambda?     => false
 *   Proc.new(&proc {}).lambda? => false
 *
 * A Proc object generated by & argument has the tricks
 *
 *   def n(&b) b.lambda? end
 *   n {}                       => false
 *
 * The & argument preserves the tricks if a Proc object is given
 * by & argument.
 *
 *   n(&lambda {})              => true
 *   n(&proc {})                => false
 *   n(&Proc.new {})            => false
 *
 * A Proc object converted from a method has no tricks.
 *
 *   def m() end
 *   method(:m).to_proc.lambda? => true
 *
 *   n(&method(:m))             => true
 *   n(&method(:m).to_proc)     => true
 *
 * define_method is treated same as method definition.
 * The defined method has no tricks.
 *
 *   class C
 *     define_method(:d) {}
 *   end
 *   C.new.e(1,2)       => ArgumentError
 *   C.new.method(:d).to_proc.lambda?   => true
 *
 * define_method always defines a method without the tricks,
 * even if a non-lambda Proc object is given.
 * This is the only exception which the tricks are not preserved.
 *
 *   class C
 *     define_method(:e, &proc {})
 *   end
 *   C.new.e(1,2)       => ArgumentError
 *   C.new.method(:e).to_proc.lambda?   => true
 *
 * This exception is for a wrapper of define_method.
 * It eases defining a method defining method which defines a usual method which has no tricks.
 *
 *   class << C
 *     def def2(name, &body)
 *       define_method(name, &body)
 *     end
 *   end
 *   class C
 *     def2(:f) {}
 *   end
 *   C.new.f(1,2)       => ArgumentError
 *
 * The wrapper, def2, defines a method which has no tricks.
 *
 */

static VALUE
proc_lambda_p(VALUE procval, SEL sel)
{
    rb_vm_block_t *proc;
    GetProcPtr(procval, proc);

    return (proc->flags & VM_BLOCK_LAMBDA) == VM_BLOCK_LAMBDA
	? Qtrue : Qfalse;
}

VALUE
rb_proc_lambda_p(VALUE procval)
{
    return proc_lambda_p(procval, 0);
}

/* Binding */

static VALUE
binding_alloc(VALUE klass)
{
    VALUE obj;
    rb_vm_binding_t *bind;
    obj = Data_Make_Struct(klass, rb_vm_binding_t,
			   NULL, NULL, bind);
    return obj;
}

static VALUE
binding_dup(VALUE self, SEL sel)
{
    VALUE bindval = binding_alloc(rb_cBinding);
    rb_vm_binding_t *src, *dst;
    GetBindingPtr(self, src);
    GetBindingPtr(bindval, dst);
    GC_WB(&dst->self, src->self);
    GC_WB(&dst->next, src->next);
    GC_WB(&dst->locals, src->locals);
    GC_WB(&dst->outer_stack, src->outer_stack);
    GC_WB(&dst->block, src->block);
    return bindval;
}

static VALUE
binding_clone(VALUE self, SEL sel)
{
    VALUE bindval = binding_dup(self, 0);
    CLONESETUP(bindval, self);
    return bindval;
}

VALUE
rb_binding_new(void)
{
    rb_vm_binding_t *bind = rb_vm_current_binding();
    if (bind == NULL) {
	// Should very rarely happen (when the compiler does not generate a
        // binding).
	rb_raise(rb_eRuntimeError, "current binding not defined");
    }
    return Data_Wrap_Struct(rb_cBinding, NULL, NULL, bind);
}

VALUE
rb_binding_new_from_binding(rb_vm_binding_t *bind)
{
    return Data_Wrap_Struct(rb_cBinding, NULL, NULL, bind);
}

/*
 *  call-seq:
 *     binding -> a_binding
 *  
 *  Returns a +Binding+ object, describing the variable and
 *  method bindings at the point of call. This object can be used when
 *  calling +eval+ to execute the evaluated command in this
 *  environment. Also see the description of class +Binding+.
 *     
 *     def getBinding(param)
 *       return binding
 *     end
 *     b = getBinding("hello")
 *     eval("param", b)   #=> "hello"
 */

static VALUE
rb_f_binding(VALUE self, SEL sel)
{
    return rb_binding_new();
}

/*
 *  call-seq:
 *     binding.eval(string [, filename [,lineno]])  => obj
 *
 *  Evaluates the Ruby expression(s) in <em>string</em>, in the
 *  <em>binding</em>'s context.  If the optional <em>filename</em> and
 *  <em>lineno</em> parameters are present, they will be used when
 *  reporting syntax errors.
 *
 *     def getBinding(param)
 *       return binding
 *     end
 *     b = getBinding("hello")
 *     b.eval("param")   #=> "hello"
 */

VALUE rb_f_eval(VALUE self, SEL sel, int argc, VALUE *argv);

static VALUE
bind_eval(VALUE bindval, SEL sel, int argc, VALUE *argv)
{
    VALUE args[4];

    rb_scan_args(argc, argv, "12", &args[0], &args[2], &args[3]);
    args[1] = bindval;
    return rb_f_eval(Qnil, 0, argc+1, args /* self will be searched in eval */);
}

static VALUE
proc_new(VALUE klass, bool is_lambda)
{
    rb_vm_block_t *block = rb_vm_first_block();
    if (block == NULL) {
	rb_raise(rb_eArgError,
		"tried to create Proc object without a block");
    }
    if (is_lambda) {
	block->flags |= VM_BLOCK_LAMBDA;
    }
    return rb_proc_alloc_with_block(klass, block);
}

/*
 *  call-seq:
 *     Proc.new {|...| block } => a_proc
 *     Proc.new                => a_proc
 *  
 *  Creates a new <code>Proc</code> object, bound to the current
 *  context. <code>Proc::new</code> may be called without a block only
 *  within a method with an attached block, in which case that block is
 *  converted to the <code>Proc</code> object.
 *     
 *     def proc_from
 *       Proc.new
 *     end
 *     proc = proc_from { "hello" }
 *     proc.call   #=> "hello"
 */

static VALUE
rb_proc_s_new(VALUE klass, SEL sel, int argc, VALUE *argv)
{
    VALUE block = proc_new(klass, false);

    rb_obj_call_init(block, argc, argv);
    return block;
}

/*
 * call-seq:
 *   proc   { |...| block }  => a_proc
 *
 * Equivalent to <code>Proc.new</code>.
 */

VALUE
rb_block_proc(void)
{
    return proc_new(rb_cProc, false);
}

VALUE
rb_block_proc_imp(void)
{
    return rb_block_proc();
}

VALUE
rb_block_lambda(void)
{
    return proc_new(rb_cProc, true);
}

VALUE
rb_f_lambda(void)
{
    rb_warn("rb_f_lambda() is deprecated; use rb_block_proc() instead");
    return rb_block_lambda();
}

/*
 * call-seq:
 *   lambda { |...| block }  => a_proc
 *
 * Equivalent to <code>Proc.new</code>, except the resulting Proc objects
 * check the number of parameters passed when called.
 */

static VALUE
proc_lambda(VALUE klass, SEL sel)
{
    return rb_block_lambda();
}

/* CHECKME: are the argument checking semantics correct? */

/*
 *  call-seq:
 *     prc.call(params,...)   => obj
 *     prc[params,...]        => obj
 *  
 *  Invokes the block, setting the block's parameters to the values in
 *  <i>params</i> using something close to method calling semantics.
 *  Generates a warning if multiple values are passed to a proc that
 *  expects just one (previously this silently converted the parameters
 *  to an array).
 *
 *  For procs created using <code>Kernel.proc</code>, generates an
 *  error if the wrong number of parameters
 *  are passed to a proc with multiple parameters. For procs created using
 *  <code>Proc.new</code>, extra parameters are silently discarded.
 *
 *  Returns the value of the last expression evaluated in the block. See
 *  also <code>Proc#yield</code>.
 *     
 *     a_proc = Proc.new {|a, *b| b.collect {|i| i*a }}
 *     a_proc.call(9, 1, 2, 3)   #=> [9, 18, 27]
 *     a_proc[9, 1, 2, 3]        #=> [9, 18, 27]
 *     a_proc = Proc.new {|a,b| a}
 *     a_proc.call(1,2,3)
 *     
 *  <em>produces:</em>
 *     
 *     prog.rb:5: wrong number of arguments (3 for 2) (ArgumentError)
 *     	from prog.rb:4:in `call'
 *     	from prog.rb:5
 */

static VALUE
proc_call(VALUE procval, SEL sel, int argc, const VALUE *argv)
{
#if 0
    rb_proc_t *proc;
    rb_block_t *blockptr = 0;
    GetProcPtr(procval, proc);

    if (BUILTIN_TYPE(proc->block.iseq) != T_NODE &&
	proc->block.iseq->arg_block != -1) {

	if (rb_block_given_p()) {
	    rb_proc_t *proc;
	    VALUE procval;
	    procval = rb_block_proc();
	    GetProcPtr(procval, proc);
	    blockptr = &proc->block;
	}
    }

    return vm_invoke_proc(GET_THREAD(), proc, proc->block.self,
			  argc, argv, blockptr);
#endif
    rb_vm_block_t *proc;
    GetProcPtr(procval, proc);
    return rb_vm_block_eval(proc, argc, argv);
}

VALUE
rb_proc_call(VALUE self, VALUE args)
{
#if 0
    rb_proc_t *proc;
    GetProcPtr(self, proc);
    return vm_invoke_proc(GET_THREAD(), proc, proc->block.self,
			  RARRAY_LEN(args), RARRAY_PTR(args), 0);
#endif
    return proc_call(self, 0, RARRAY_LEN(args), RARRAY_PTR(args));
}

VALUE
rb_proc_call2(VALUE self, int argc, VALUE *argv)
{
    return proc_call(self, 0, argc, argv);
}

VALUE
rb_proc_check_and_call(VALUE proc, int argc, VALUE *argv)
{
    VALUE tmp = rb_check_convert_type(proc, T_DATA, "Proc", "to_proc");
    if (NIL_P(tmp)) {
        rb_raise(rb_eTypeError,
		"wrong type %s (expected Proc)",
		rb_obj_classname(proc));
    }
    proc = tmp;

    const int arity = rb_proc_arity(proc);
    if (arity != argc) {
	rb_raise(rb_eArgError, "expected Proc with %d arguments (got %d)",
		argc, arity);
    }
    return proc_call(proc, 0, argc, argv);
}

/*
 *  call-seq:
 *     prc.arity -> fixnum
 *  
 *  Returns the number of arguments that would not be ignored. If the block
 *  is declared to take no arguments, returns 0. If the block is known
 *  to take exactly n arguments, returns n. If the block has optional
 *  arguments, return -n-1, where n is the number of mandatory
 *  arguments. A <code>proc</code> with no argument declarations
 *  is the same a block declaring <code>||</code> as its arguments.
 *     
 *     Proc.new {}.arity          #=>  0
 *     Proc.new {||}.arity        #=>  0
 *     Proc.new {|a|}.arity       #=>  1
 *     Proc.new {|a,b|}.arity     #=>  2
 *     Proc.new {|a,b,c|}.arity   #=>  3
 *     Proc.new {|*a|}.arity      #=> -1
 *     Proc.new {|a,*b|}.arity    #=> -2
 *     Proc.new {|a,*b, c|}.arity    #=> -3
 */

static inline int
method_arity(VALUE method)
{
    rb_vm_method_t *data;
    Data_Get_Struct(method, rb_vm_method_t, data);
    return data->arity;
}

static VALUE
proc_arity(VALUE self, SEL sel)
{
    return INT2FIX(rb_proc_arity(self));
}

int
rb_proc_arity(VALUE proc)
{
    rb_vm_block_t *b;
    GetProcPtr(proc, b);
    return rb_vm_arity_n(b->arity);
}

#if 0
static rb_iseq_t *
get_proc_iseq(VALUE self)
{
    rb_proc_t *proc;
    rb_iseq_t *iseq;

    GetProcPtr(self, proc);
    iseq = proc->block.iseq;
    if (!RUBY_VM_NORMAL_ISEQ_P(iseq))
	return 0;
    return iseq;
}

VALUE
rb_proc_location(VALUE self)
{
    rb_iseq_t *iseq = get_proc_iseq(self);
    VALUE loc[2];

    if (!iseq) return Qnil;
    loc[0] = iseq->filename;
    if (iseq->insn_info_table) {
	loc[1] = INT2FIX(iseq->insn_info_table[0].line_no);
    }
    else {
	loc[1] = Qnil;
    }
    return rb_ary_new4(2, loc);
}
#endif

/*
 * call-seq:
 *   prc == other_proc   =>  true or false
 *
 * Return <code>true</code> if <i>prc</i> is the same object as
 * <i>other_proc</i>, or if they are both procs with the same body.
 */

static VALUE
proc_eq(VALUE self, SEL sel, VALUE other)
{
    if (self == other) {
	return Qtrue;
    }
    else if (rb_obj_is_kind_of(other, rb_cProc)) {
	rb_vm_block_t *self_b, *other_b;
	GetProcPtr(self, self_b);
	GetProcPtr(other, other_b);
	return self_b == other_b ? Qtrue : Qfalse;
    }
    return Qfalse;
}

/*
 * call-seq:
 *   prc.hash   =>  integer
 *
 * Return hash value corresponding to proc body.
 */

static VALUE
proc_hash(VALUE self, SEL sel)
{
    rb_vm_block_t *b;
    GetProcPtr(self, b);
    return LONG2FIX(b);
}

/*
 * call-seq:
 *   prc.to_s   => string
 *
 * Shows the unique identifier for this proc, along with
 * an indication of where the proc was defined.
 */

static VALUE
proc_to_s(VALUE self, SEL sel)
{
    const char		*cname = rb_obj_classname(self);
    rb_vm_block_t	*proc;

    GetProcPtr(self, proc);

    const char *is_lambda = (proc->flags & VM_BLOCK_LAMBDA) ? " (lambda)" : "";
    VALUE str = rb_sprintf("#<%s:%p%s>", cname, (void *)self, is_lambda);

    if (OBJ_TAINTED(self)) {
	OBJ_TAINT(str);
    }

    return str;
}

#if 0 // TODO
static VALUE
proc_to_s(VALUE self, SEL sel)
{
    VALUE str = 0;
    rb_proc_t *proc;
    const char *cname = rb_obj_classname(self);
    rb_iseq_t *iseq;
    const char *is_lambda;
    
    GetProcPtr(self, proc);
    iseq = proc->block.iseq;
    is_lambda = proc->is_lambda ? " (lambda)" : "";

    if (RUBY_VM_NORMAL_ISEQ_P(iseq)) {
	int line_no = 0;
	
	if (iseq->insn_info_table) {
	    line_no = iseq->insn_info_table[0].line_no;
	}
	str = rb_sprintf("#<%s:%p@%s:%d%s>", cname, (void *)self,
			 RSTRING_PTR(iseq->filename),
			 line_no, is_lambda);
    }
    else {
	str = rb_sprintf("#<%s:%p%s>", cname, proc->block.iseq,
			 is_lambda);
    }

    if (OBJ_TAINTED(self)) {
	OBJ_TAINT(str);
    }
    return str;
}
#endif

/*
 *  call-seq:
 *     prc.to_proc -> prc
 *  
 *  Part of the protocol for converting objects to <code>Proc</code>
 *  objects. Instances of class <code>Proc</code> simply return
 *  themselves.
 */

static VALUE
proc_to_proc(VALUE self, SEL sel)
{
    return self;
}

NODE *rb_get_method_body(VALUE klass, ID id, ID *idp);
void rb_print_undef(VALUE klass, ID id, int scope);

static inline VALUE
mnew(VALUE klass, VALUE obj, ID id, VALUE mclass, int scope)
{
    rb_vm_method_t *m = rb_vm_get_method(klass, obj, id, scope);
    assert(m != NULL);

    if (m->node) {
	const int flag = m->node->flags & NOEX_MASK;
	if (scope && flag != NOEX_PUBLIC) {
	    const char *v = "";
	    switch (flag) {
	      case NOEX_PRIVATE:
		v = "private";
		break;
	      case NOEX_PROTECTED:
		v = "protected";
		break;
	    }
	    rb_name_error(id, "method `%s' for %s `%s' is %s",
			  rb_id2name(id),
			  (TYPE(klass) == T_MODULE) ? "module" : "class",
			  rb_class2name(klass),
			  v);
	}
    }

    return Data_Wrap_Struct(mclass, NULL, NULL, m);
}

/**********************************************************************
 *
 * Document-class : Method
 *
 *  Method objects are created by <code>Object#method</code>, and are
 *  associated with a particular object (not just with a class). They
 *  may be used to invoke the method within the object, and as a block
 *  associated with an iterator. They may also be unbound from one
 *  object (creating an <code>UnboundMethod</code>) and bound to
 *  another.
 *     
 *     class Thing
 *       def square(n)
 *         n*n
 *       end
 *     end
 *     thing = Thing.new
 *     meth  = thing.method(:square)
 *     
 *     meth.call(9)                 #=> 81
 *     [ 1, 2, 3 ].collect(&meth)   #=> [1, 4, 9]
 *     
 */

/*
 * call-seq:
 *   meth == other_meth  => true or false
 *
 * Two method objects are equal if that are bound to the same
 * object and contain the same body.
 */


static VALUE
method_eq(VALUE method, SEL sel, VALUE other)
{
    rb_vm_method_t *m1, *m2;

    if (CLASS_OF(method) != CLASS_OF(other)) {
	return Qfalse;
    }

    Data_Get_Struct(method, rb_vm_method_t, m1);
    Data_Get_Struct(other, rb_vm_method_t, m2);

    if (m1->oclass != m2->oclass
	|| m1->rclass != m2->rclass
	|| m1->recv != m2->recv) {
	return Qfalse;
    }

    IMP m1_imp = m1->node == NULL
	? class_getMethodImplementation((Class)m1->oclass, m1->sel)
	: m1->node->objc_imp;
    IMP m2_imp = m2->node == NULL
	? class_getMethodImplementation((Class)m2->oclass, m2->sel)
	: m2->node->objc_imp;
    if (m1_imp != m2_imp) {
	return Qfalse;
    }

    return Qtrue;
}

/*
 * call-seq:
 *    meth.hash   => integer
 *
 * Return a hash value corresponding to the method object.
 */

static VALUE
method_hash(VALUE method, SEL sel)
{
    rb_vm_method_t *m;
    long hash;

    Data_Get_Struct(method, rb_vm_method_t, m);
    hash = (long)m->oclass;
    hash ^= (long)m->rclass;
    hash ^= (long)m->recv;
    hash ^= (long)m->node;

    return INT2FIX(hash);
}

/*
 *  call-seq:
 *     meth.unbind    => unbound_method
 *  
 *  Dissociates <i>meth</i> from it's current receiver. The resulting
 *  <code>UnboundMethod</code> can subsequently be bound to a new object
 *  of the same class (see <code>UnboundMethod</code>).
 */

static VALUE
method_unbind(VALUE obj, SEL sel)
{
    VALUE method;
    rb_vm_method_t *orig, *data;

    Data_Get_Struct(obj, rb_vm_method_t, orig);
    method =
	Data_Make_Struct(rb_cUnboundMethod, rb_vm_method_t, NULL, NULL, data);
    data->oclass = orig->oclass;
    data->recv = Qundef;
    data->node = orig->node;
    data->rclass = orig->rclass;
    data->sel = orig->sel;
    data->cache = orig->cache;
    data->arity = orig->arity;

    return method;
}

/*
 *  call-seq:
 *     meth.receiver    => object
 *  
 *  Returns the bound receiver of the method object.
 */

static VALUE
method_receiver(VALUE obj, SEL sel)
{
    rb_vm_method_t *data;
    Data_Get_Struct(obj, rb_vm_method_t, data);
    return data->recv;
}

/*
 *  call-seq:
 *     meth.name    => symbol
 *  
 *  Returns the name of the method.
 */

static VALUE
method_name(VALUE obj, SEL sel)
{
    rb_vm_method_t *data;
    Data_Get_Struct(obj, rb_vm_method_t, data);
    ID mid = rb_intern(sel_getName(data->sel));
    return ID2SYM(mid);
}

/*
 *  call-seq:
 *     meth.owner    => class_or_module
 *  
 *  Returns the class or module that defines the method.
 */

static VALUE
method_owner(VALUE obj, SEL sel)
{
    rb_vm_method_t *data;
    Data_Get_Struct(obj, rb_vm_method_t, data);
    return data->oclass;
}

/*
 *  call-seq:
 *     obj.method(sym)    => method
 *  
 *  Looks up the named method as a receiver in <i>obj</i>, returning a
 *  <code>Method</code> object (or raising <code>NameError</code>). The
 *  <code>Method</code> object acts as a closure in <i>obj</i>'s object
 *  instance, so instance variables and the value of <code>self</code>
 *  remain available.
 *     
 *     class Demo
 *       def initialize(n)
 *         @iv = n
 *       end
 *       def hello()
 *         "Hello, @iv = #{@iv}"
 *       end
 *     end
 *     
 *     k = Demo.new(99)
 *     m = k.method(:hello)
 *     m.call   #=> "Hello, @iv = 99"
 *     
 *     l = Demo.new('Fred')
 *     m = l.method("hello")
 *     m.call   #=> "Hello, @iv = Fred"
 */

static VALUE
rb_obj_method(VALUE obj, SEL sel, VALUE vid)
{
    return mnew(CLASS_OF(obj), obj, rb_to_id(vid), rb_cMethod, Qfalse);
}

static VALUE
rb_obj_public_method(VALUE obj, SEL sel, VALUE vid)
{
    return mnew(CLASS_OF(obj), obj, rb_to_id(vid), rb_cMethod, Qtrue);
}

/*
 *  call-seq:
 *     mod.instance_method(symbol)   => unbound_method
 *  
 *  Returns an +UnboundMethod+ representing the given
 *  instance method in _mod_.
 *     
 *     class Interpreter
 *       def do_a() print "there, "; end
 *       def do_d() print "Hello ";  end
 *       def do_e() print "!\n";     end
 *       def do_v() print "Dave";    end
 *       Dispatcher = {
 *        ?a => instance_method(:do_a),
 *        ?d => instance_method(:do_d),
 *        ?e => instance_method(:do_e),
 *        ?v => instance_method(:do_v)
 *       }
 *       def interpret(string)
 *         string.each_byte {|b| Dispatcher[b].bind(self).call }
 *       end
 *     end
 *     
 *     
 *     interpreter = Interpreter.new
 *     interpreter.interpret('dave')
 *     
 *  <em>produces:</em>
 *     
 *     Hello there, Dave!
 */

static VALUE
rb_mod_instance_method(VALUE mod, SEL sel, VALUE vid)
{
    return mnew(mod, Qundef, rb_to_id(vid), rb_cUnboundMethod, Qfalse);
}

static VALUE
rb_mod_public_instance_method(VALUE mod, SEL sel, VALUE vid)
{
    return mnew(mod, Qundef, rb_to_id(vid), rb_cUnboundMethod, Qtrue);
}

/*
 *  call-seq:
 *     define_method(symbol, method)     => new_method
 *     define_method(symbol) { block }   => proc
 *  
 *  Defines an instance method in the receiver. The _method_
 *  parameter can be a +Proc+ or +Method+ object.
 *  If a block is specified, it is used as the method body. This block
 *  is evaluated using <code>instance_eval</code>, a point that is
 *  tricky to demonstrate because <code>define_method</code> is private.
 *  (This is why we resort to the +send+ hack in this example.)
 *     
 *     class A
 *       def fred
 *         puts "In Fred"
 *       end
 *       def create_method(name, &block)
 *         self.class.send(:define_method, name, &block)
 *       end
 *       define_method(:wilma) { puts "Charge it!" }
 *     end
 *     class B < A
 *       define_method(:barney, instance_method(:fred))
 *     end
 *     a = B.new
 *     a.barney
 *     a.wilma
 *     a.create_method(:betty) { p self }
 *     a.betty
 *     
 *  <em>produces:</em>
 *     
 *     In Fred
 *     Charge it!
 *     #<B:0x401b39e8>
 */

static VALUE
rb_mod_define_method(VALUE mod, SEL sel, int argc, VALUE *argv)
{
#if MACRUBY_STATIC
    not_implemented_in_static(sel);
#else
    ID id;
    VALUE body;

    if (argc == 1) {
	id = rb_to_id(argv[0]);
	body = rb_block_lambda();
    }
    else if (argc == 2) {
	id = rb_to_id(argv[0]);
	body = argv[1];
	if (!rb_obj_is_method(body) && !rb_obj_is_proc(body)) {
	    rb_raise(rb_eTypeError,
		     "wrong argument type %s (expected Proc/Method)",
		     rb_obj_classname(body));
	}
    }
    else {
	rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }

    if (rb_obj_is_method(body)) {
	rb_vm_method_t *data;
	Data_Get_Struct(body, rb_vm_method_t, data);
	if (data->node == NULL) {
	    rb_raise(rb_eArgError, "cannot use Method object of pure Objective-C method");
	}
	VALUE klass = data->rclass;
	if (RBASIC(mod)->klass != klass && !RTEST(rb_class_inherited_p(mod, klass))) {
	    rb_raise(rb_eTypeError,
		     "bind argument must be a subclass of %s",
		     rb_class2name(klass));
	}
	SEL msel = rb_vm_id_to_sel(id, data->arity);
	rb_vm_define_method2((Class)mod, msel, data->node, data->node->flags, false);
    }
    else {
	rb_vm_block_t *proc;
	GetProcPtr(body, proc);
	rb_vm_define_method3((Class)mod, id, proc);
    }

    return body;
#endif
}

static VALUE
rb_obj_define_method(VALUE obj, SEL sel, int argc, VALUE *argv)
{
    VALUE klass = rb_singleton_class(obj);

    return rb_mod_define_method(klass, 0, argc, argv);
}


/*
 * MISSING: documentation
 */

static VALUE
method_clone(VALUE self, SEL sel)
{
    VALUE clone;
    rb_vm_method_t *orig, *data;

    Data_Get_Struct(self, rb_vm_method_t, orig);
    clone =
	Data_Make_Struct(CLASS_OF(self), rb_vm_method_t, NULL, NULL, data);
    CLONESETUP(clone, self);
    *data = *orig;
    GC_WB(&data->recv, orig->recv);

    return clone;
}

/*
 *  call-seq:
 *     meth.call(args, ...)    => obj
 *     meth[args, ...]         => obj
 *  
 *  Invokes the <i>meth</i> with the specified arguments, returning the
 *  method's return value.
 *     
 *     m = 12.method("+")
 *     m.call(3)    #=> 15
 *     m.call(20)   #=> 32
 */

VALUE
rb_method_call(VALUE method, SEL sel, int argc, VALUE *argv)
{
    rb_vm_method_t *data;

    Data_Get_Struct(method, rb_vm_method_t, data);
    if (data->recv == Qundef) {
	rb_raise(rb_eTypeError, "can't call unbound method; bind first");
    }
    
    int safe = -1;
    if (OBJ_TAINTED(method)) {
	safe = rb_safe_level();
	if (rb_safe_level() < 4) {
	    rb_set_safe_level_force(4);
	}
    }

    VALUE result = rb_vm_method_call(data, rb_vm_current_block(), argc, argv);

    if (safe >= 0) {
	rb_set_safe_level_force(safe);
    }

    return result;
}

/**********************************************************************
 *
 * Document-class: UnboundMethod
 *
 *  Ruby supports two forms of objectified methods. Class
 *  <code>Method</code> is used to represent methods that are associated
 *  with a particular object: these method objects are bound to that
 *  object. Bound method objects for an object can be created using
 *  <code>Object#method</code>.
 *     
 *  Ruby also supports unbound methods; methods objects that are not
 *  associated with a particular object. These can be created either by
 *  calling <code>Module#instance_method</code> or by calling
 *  <code>unbind</code> on a bound method object. The result of both of
 *  these is an <code>UnboundMethod</code> object.
 *     
 *  Unbound methods can only be called after they are bound to an
 *  object. That object must be be a kind_of? the method's original
 *  class.
 *     
 *     class Square
 *       def area
 *         @side * @side
 *       end
 *       def initialize(side)
 *         @side = side
 *       end
 *     end
 *     
 *     area_un = Square.instance_method(:area)
 *     
 *     s = Square.new(12)
 *     area = area_un.bind(s)
 *     area.call   #=> 144
 *     
 *  Unbound methods are a reference to the method at the time it was
 *  objectified: subsequent changes to the underlying class will not
 *  affect the unbound method.
 *     
 *     class Test
 *       def test
 *         :original
 *       end
 *     end
 *     um = Test.instance_method(:test)
 *     class Test
 *       def test
 *         :modified
 *       end
 *     end
 *     t = Test.new
 *     t.test            #=> :modified
 *     um.bind(t).call   #=> :original
 *     
 */

/*
 *  call-seq:
 *     umeth.bind(obj) -> method
 *  
 *  Bind <i>umeth</i> to <i>obj</i>. If <code>Klass</code> was the class
 *  from which <i>umeth</i> was obtained,
 *  <code>obj.kind_of?(Klass)</code> must be true.
 *     
 *     class A
 *       def test
 *         puts "In test, class = #{self.class}"
 *       end
 *     end
 *     class B < A
 *     end
 *     class C < B
 *     end
 *     
 *     
 *     um = B.instance_method(:test)
 *     bm = um.bind(C.new)
 *     bm.call
 *     bm = um.bind(B.new)
 *     bm.call
 *     bm = um.bind(A.new)
 *     bm.call
 *     
 *  <em>produces:</em>
 *     
 *     In test, class = C
 *     In test, class = B
 *     prog.rb:16:in `bind': bind argument must be an instance of B (TypeError)
 *     	from prog.rb:16
 */

static VALUE
umethod_bind(VALUE method, SEL sel, VALUE recv)
{
    rb_vm_method_t *data, *bound;

    Data_Get_Struct(method, rb_vm_method_t, data);
    if (data->rclass != CLASS_OF(recv) && !rb_obj_is_kind_of(recv, data->rclass)) {
	if (RCLASS_SINGLETON(data->rclass)) {
	    rb_raise(rb_eTypeError,
		     "singleton method called for a different object");
	}
	else {
	    rb_raise(rb_eTypeError, "bind argument must be an instance of %s",
		     rb_class2name(data->rclass));
	}
    }

    method = Data_Make_Struct(rb_cMethod, rb_vm_method_t, NULL, NULL, bound);
    *bound = *data;
    GC_WB(&bound->recv, recv);
    bound->rclass = CLASS_OF(recv);

    return method;
}

int
rb_node_arity(NODE* body)
{
    // TODO should be replaced by the roxor.cpp's stuff
    switch (nd_type(body)) {
	case NODE_CFUNC:
	    if (body->nd_argc < 0) {
		return -1;
	    }
	    return body->nd_argc;
	case NODE_ZSUPER:
	    return -1;
	case NODE_ATTRSET:
	    return 1;
	case NODE_IVAR:
	    return 0;
	case NODE_BMETHOD:
	    return rb_proc_arity(body->nd_cval);
	default:
	    rb_raise(rb_eArgError, "invalid node 0x%x", nd_type(body));
    }
}

/*
 *  call-seq:
 *     meth.arity    => fixnum
 *  
 *  Returns an indication of the number of arguments accepted by a
 *  method. Returns a nonnegative integer for methods that take a fixed
 *  number of arguments. For Ruby methods that take a variable number of
 *  arguments, returns -n-1, where n is the number of required
 *  arguments. For methods written in C, returns -1 if the call takes a
 *  variable number of arguments.
 *     
 *     class C
 *       def one;    end
 *       def two(a); end
 *       def three(*a);  end
 *       def four(a, b); end
 *       def five(a, b, *c);    end
 *       def six(a, b, *c, &d); end
 *     end
 *     c = C.new
 *     c.method(:one).arity     #=> 0
 *     c.method(:two).arity     #=> 1
 *     c.method(:three).arity   #=> -1
 *     c.method(:four).arity    #=> 2
 *     c.method(:five).arity    #=> -3
 *     c.method(:six).arity     #=> -3
 *     
 *     "cat".method(:size).arity      #=> 0
 *     "cat".method(:replace).arity   #=> 1
 *     "cat".method(:squeeze).arity   #=> -1
 *     "cat".method(:count).arity     #=> -1
 */

static VALUE
method_arity_m(VALUE method, SEL sel)
{
    int n = method_arity(method);
    return INT2FIX(n);
}

/*
 *  call-seq:
 *   meth.to_s      =>  string
 *   meth.inspect   =>  string
 *
 *  Show the name of the underlying method.
 *
 *    "cat".method(:count).inspect   #=> "#<Method: String#count>"
 */

static VALUE
method_inspect(VALUE method, SEL sel)
{
    rb_vm_method_t *data;
    VALUE str;
    const char *s;
    const char *sharp = "#";

    Data_Get_Struct(method, rb_vm_method_t, data);
    str = rb_str_buf_new2("#<");
    s = rb_obj_classname(method);
    rb_str_buf_cat2(str, s);
    rb_str_buf_cat2(str, ": ");

    rb_str_buf_cat2(str, rb_class2name(data->rclass));
    if (data->rclass != data->oclass) {
	rb_str_buf_cat2(str, "(");
	rb_str_buf_cat2(str, rb_class2name(data->oclass));
	rb_str_buf_cat2(str, ")");
    }
    rb_str_buf_cat2(str, sharp);
    rb_str_buf_cat2(str, sel_getName(data->sel));
    rb_str_buf_cat2(str, ">");

    return str;
}

static VALUE
mproc(VALUE method)
{
    return rb_funcall(Qnil, rb_intern("proc"), 0);
}

#if 0
static VALUE
mlambda(VALUE method)
{
    return rb_funcall(Qnil, rb_intern("lambda"), 0);
}
#endif

#if 0
static VALUE
bmcall(VALUE args, VALUE method)
{
    volatile VALUE a;

#if WITH_OBJC
    if (TYPE(args) != T_ARRAY) {
    	return rb_method_call(1, &args, method);
    }
#else
    if (CLASS_OF(args) != rb_cArray) {
	args = rb_ary_new3(1, args);
    }
#endif

    a = args;
    return rb_method_call(RARRAY_LEN(a), (VALUE *)RARRAY_PTR(a), method);
}
#endif

VALUE
rb_proc_new(
    VALUE (*func)(ANYARGS), /* VALUE yieldarg[, VALUE procarg] */
    VALUE val)
{
    VALUE procval = rb_iterate(mproc, 0, func, val);
    return procval;
}

/*
 *  call-seq:
 *     meth.to_proc    => prc
 *  
 *  Returns a <code>Proc</code> object corresponding to this method.
 */

static VALUE
method_proc(VALUE method, SEL sel)
{
    rb_vm_method_t *data;
    Data_Get_Struct(method, rb_vm_method_t, data);
    rb_vm_block_t *block = rb_vm_create_block_from_method(data);
    return rb_proc_alloc_with_block(rb_cProc, block);
}

/*
 * call_seq:
 *   local_jump_error.exit_value  => obj
 *
 * Returns the exit value associated with this +LocalJumpError+.
 */
static VALUE
localjump_xvalue(VALUE exc, SEL sel)
{
    return rb_iv_get(exc, "@exit_value");
}

/*
 * call-seq:
 *    local_jump_error.reason   => symbol
 *
 * The reason this block was terminated:
 * :break, :redo, :retry, :next, :return, or :noreason.
 */

static VALUE
localjump_reason(VALUE exc, SEL sel)
{
    return rb_iv_get(exc, "@reason");
}

/*
 *  call-seq:
 *     prc.binding    => binding
 *  
 *  Returns the binding associated with <i>prc</i>. Note that
 *  <code>Kernel#eval</code> accepts either a <code>Proc</code> or a
 *  <code>Binding</code> object as its second parameter.
 *     
 *     def fred(param)
 *       proc {}
 *     end
 *     
 *     b = fred(99)
 *     eval("param", b.binding)   #=> 99
 */
static VALUE
proc_binding(VALUE self, SEL sel)
{
    rb_vm_block_t *block;
    GetProcPtr(self, block);

    rb_vm_binding_t *binding = (rb_vm_binding_t *)xmalloc(
	    sizeof(rb_vm_binding_t));

    binding->block = NULL;
    GC_WB(&binding->self, block->self);
    GC_WB(&binding->locals, block->locals);
    binding->outer_stack = NULL;

    return Data_Wrap_Struct(rb_cBinding, NULL, NULL, binding);
}

 /*
  *  call-seq:
  *     prc.curry         => a_proc
  *     prc.curry(arity)  => a_proc
  *
  *  Returns a curried proc. If the optional <i>arity</i> argument is given,
  *  it determines the number of arguments.
  *  A curried proc receives some arguments. If a sufficient number of
  *  arguments are supplied, it passes the supplied arguments to the original
  *  proc and returns the result. Otherwise, returns another curried proc that
  *  takes the rest of arguments.
  *
  *     b = proc {|x, y, z| (x||0) + (y||0) + (z||0) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 6
  *     p b.curry(5)[1][2][3][4][5]  #=> 6
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 6
  *     p b.curry(1)[1]              #=> 1
  *
  *     b = proc {|x, y, z, *w| (x||0) + (y||0) + (z||0) + w.inject(0, &:+) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 10
  *     p b.curry(5)[1][2][3][4][5]  #=> 15
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 15
  *     p b.curry(1)[1]              #=> 1
  *
  *     b = lambda {|x, y, z| (x||0) + (y||0) + (z||0) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> wrong number of arguments (4 or 3)
  *     p b.curry(5)                 #=> wrong number of arguments (5 or 3)
  *     p b.curry(1)                 #=> wrong number of arguments (1 or 3)
  *
  *     b = lambda {|x, y, z, *w| (x||0) + (y||0) + (z||0) + w.inject(0, &:+) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 10
  *     p b.curry(5)[1][2][3][4][5]  #=> 15
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 15
  *     p b.curry(1)                 #=> wrong number of arguments (1 or 3)
  *
  *     b = proc { :foo }
  *     p b.curry[]                  #=> :foo
  */
static VALUE
proc_curry(VALUE self, SEL sel, int argc, VALUE *argv)
{
    int sarity, marity = FIX2INT(proc_arity(self, 0));
    VALUE arity, opt = Qfalse;

    if (marity < 0) {
	marity = -marity - 1;
	opt = Qtrue;
    }

    rb_scan_args(argc, argv, "01", &arity);
    if (NIL_P(arity)) {
	arity = INT2FIX(marity);
    }
    else {
	sarity = FIX2INT(arity);
	if (proc_lambda_p(self, 0) && (sarity < marity || (sarity > marity && !opt))) {
	    rb_raise(rb_eArgError, "wrong number of arguments (%d for %d)", sarity, marity);
	}
    }

    return rb_vm_make_curry_proc(self, rb_ary_new(), arity);
}

/*
 *  <code>Proc</code> objects are blocks of code that have been bound to
 *  a set of local variables. Once bound, the code may be called in
 *  different contexts and still access those variables.
 *     
 *     def gen_times(factor)
 *       return Proc.new {|n| n*factor }
 *     end
 *     
 *     times3 = gen_times(3)
 *     times5 = gen_times(5)
 *     
 *     times3.call(12)               #=> 36
 *     times5.call(5)                #=> 25
 *     times3.call(times5.call(4))   #=> 60
 *     
 */

extern VALUE sysstack_error; // defined in eval.c for WTF reason

void
Init_Proc(void)
{
    /* Proc */
    rb_cProc = rb_define_class("Proc", rb_cObject);
    rb_undef_alloc_func(rb_cProc);
    rb_objc_define_method(*(VALUE *)rb_cProc, "new", rb_proc_s_new, -1);
    rb_objc_define_method(rb_cProc, "call", proc_call, -1);
    rb_objc_define_method(rb_cProc, "[]", proc_call, -1);
    rb_objc_define_method(rb_cProc, "===", proc_call, -1);
    rb_objc_define_method(rb_cProc, "yield", proc_call, -1);
    rb_objc_define_method(rb_cProc, "to_proc", proc_to_proc, 0);
    rb_objc_define_method(rb_cProc, "arity", proc_arity, 0);
    rb_objc_define_method(rb_cProc, "clone", proc_clone, 0);
    rb_objc_define_method(rb_cProc, "dup", proc_dup, 0);
    rb_objc_define_method(rb_cProc, "==", proc_eq, 1);
    rb_objc_define_method(rb_cProc, "eql?", proc_eq, 1);
    rb_objc_define_method(rb_cProc, "hash", proc_hash, 0);
    rb_objc_define_method(rb_cProc, "to_s", proc_to_s, 0);
    rb_objc_define_method(rb_cProc, "lambda?", proc_lambda_p, 0);
    rb_objc_define_method(rb_cProc, "binding", proc_binding, 0);
    rb_objc_define_method(rb_cProc, "curry", proc_curry, -1);

    /* Exceptions */
    rb_eLocalJumpError = rb_define_class("LocalJumpError", rb_eStandardError);
    rb_objc_define_method(rb_eLocalJumpError, "exit_value", localjump_xvalue, 0);
    rb_objc_define_method(rb_eLocalJumpError, "reason", localjump_reason, 0);

    rb_eSysStackError = rb_define_class("SystemStackError", rb_eException);
    sysstack_error = rb_exc_new2(rb_eSysStackError, "stack level too deep");
    OBJ_TAINT(sysstack_error);
    GC_RETAIN(sysstack_error);

    /* utility functions */
    rb_objc_define_module_function(rb_mKernel, "proc", rb_block_proc_imp, 0);
    rb_objc_define_module_function(rb_mKernel, "lambda", proc_lambda, 0);

    /* Method */
    rb_cMethod = rb_define_class("Method", rb_cObject);
    rb_undef_alloc_func(rb_cMethod);
    rb_undef_method(CLASS_OF(rb_cMethod), "new");
    rb_objc_define_method(rb_cMethod, "==", method_eq, 1);
    rb_objc_define_method(rb_cMethod, "eql?", method_eq, 1);
    rb_objc_define_method(rb_cMethod, "hash", method_hash, 0);
    rb_objc_define_method(rb_cMethod, "clone", method_clone, 0);
    rb_objc_define_method(rb_cMethod, "call", rb_method_call, -1);
    rb_objc_define_method(rb_cMethod, "[]", rb_method_call, -1);
    rb_objc_define_method(rb_cMethod, "arity", method_arity_m, 0);
    rb_objc_define_method(rb_cMethod, "inspect", method_inspect, 0);
    rb_objc_define_method(rb_cMethod, "to_s", method_inspect, 0);
    rb_objc_define_method(rb_cMethod, "to_proc", method_proc, 0);
    rb_objc_define_method(rb_cMethod, "receiver", method_receiver, 0);
    rb_objc_define_method(rb_cMethod, "name", method_name, 0);
    rb_objc_define_method(rb_cMethod, "owner", method_owner, 0);
    rb_objc_define_method(rb_cMethod, "unbind", method_unbind, 0);

    rb_objc_define_method(rb_mKernel, "method", rb_obj_method, 1);
    rb_objc_define_method(rb_mKernel, "public_method", rb_obj_public_method, 1);

    /* UnboundMethod */
    rb_cUnboundMethod = rb_define_class("UnboundMethod", rb_cObject);
    rb_undef_alloc_func(rb_cUnboundMethod);
    rb_undef_method(CLASS_OF(rb_cUnboundMethod), "new");
    rb_objc_define_method(rb_cUnboundMethod, "==", method_eq, 1);
    rb_objc_define_method(rb_cUnboundMethod, "eql?", method_eq, 1);
    rb_objc_define_method(rb_cUnboundMethod, "hash", method_hash, 0);
    rb_objc_define_method(rb_cUnboundMethod, "clone", method_clone, 0);
    rb_objc_define_method(rb_cUnboundMethod, "arity", method_arity_m, 0);
    rb_objc_define_method(rb_cUnboundMethod, "inspect", method_inspect, 0);
    rb_objc_define_method(rb_cUnboundMethod, "to_s", method_inspect, 0);
    rb_objc_define_method(rb_cUnboundMethod, "name", method_name, 0);
    rb_objc_define_method(rb_cUnboundMethod, "owner", method_owner, 0);
    rb_objc_define_method(rb_cUnboundMethod, "bind", umethod_bind, 1);

    /* Module#*_method */
    rb_objc_define_method(rb_cModule, "instance_method", rb_mod_instance_method, 1);
    rb_objc_define_method(rb_cModule, "public_instance_method", rb_mod_public_instance_method, 1);
    rb_objc_define_private_method(rb_cModule, "define_method", rb_mod_define_method, -1);

    /* Kernel */
    rb_objc_define_method(rb_mKernel, "define_singleton_method", rb_obj_define_method, -1);
}

/*
 *  Objects of class <code>Binding</code> encapsulate the execution
 *  context at some particular place in the code and retain this context
 *  for future use. The variables, methods, value of <code>self</code>,
 *  and possibly an iterator block that can be accessed in this context
 *  are all retained. Binding objects can be created using
 *  <code>Kernel#binding</code>, and are made available to the callback
 *  of <code>Kernel#set_trace_func</code>.
 *     
 *  These binding objects can be passed as the second argument of the
 *  <code>Kernel#eval</code> method, establishing an environment for the
 *  evaluation.
 *     
 *     class Demo
 *       def initialize(n)
 *         @secret = n
 *       end
 *       def getBinding
 *         return binding()
 *       end
 *     end
 *     
 *     k1 = Demo.new(99)
 *     b1 = k1.getBinding
 *     k2 = Demo.new(-3)
 *     b2 = k2.getBinding
 *     
 *     eval("@secret", b1)   #=> 99
 *     eval("@secret", b2)   #=> -3
 *     eval("@secret")       #=> nil
 *     
 *  Binding objects have no class-specific methods.
 *     
 */

void
Init_Binding(void)
{
    rb_cBinding = rb_define_class("Binding", rb_cObject);
    rb_undef_alloc_func(rb_cBinding);
    rb_undef_method(CLASS_OF(rb_cBinding), "new");
    rb_objc_define_method(rb_cBinding, "clone", binding_clone, 0);
    rb_objc_define_method(rb_cBinding, "dup", binding_dup, 0);
    rb_objc_define_method(rb_cBinding, "eval", bind_eval, -1);
    rb_objc_define_module_function(rb_mKernel, "binding", rb_f_binding, 0);

    rb_vm_binding_t *binding = (rb_vm_binding_t *)xmalloc(
	    sizeof(rb_vm_binding_t));
    GC_WB(&binding->self, rb_vm_top_self());
    binding->outer_stack = NULL;
    rb_define_global_const("TOPLEVEL_BINDING",
	    rb_binding_new_from_binding(binding));
}