Proc

Proc 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

Public Class Methods

new {|...| block } => a_proc click to toggle source

new => a_proc

Creates a new Proc object, bound to the current context. Proc::new may be called without a block only within a method with an attached block, in which case that block is converted to the Proc object.

def proc_from
  Proc.new
end
proc = proc_from { "hello" }
proc.call   #=> "hello"

 
               static VALUE
proc_s_new(argc, argv, klass)
    int argc;
    VALUE *argv;
    VALUE klass;
{
    VALUE block = proc_alloc(klass, Qfalse);

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

Public Instance Methods

prc == other_proc => true or false click to toggle source

Return true if prc is the same object as other_proc, or if they are both procs with the same body.

 
               static VALUE
proc_eq(self, other)
    VALUE self, other;
{
    struct BLOCK *data, *data2;

    if (self == other) return Qtrue;
    if (TYPE(other) != T_DATA) return Qfalse;
    if (RDATA(other)->dmark != (RUBY_DATA_FUNC)blk_mark) return Qfalse;
    if (CLASS_OF(self) != CLASS_OF(other)) return Qfalse;
    Data_Get_Struct(self, struct BLOCK, data);
    Data_Get_Struct(other, struct BLOCK, data2);
    if (data->body != data2->body) return Qfalse;
    if (data->var != data2->var) return Qfalse;
    if (data->scope != data2->scope) return Qfalse;
    if (data->dyna_vars != data2->dyna_vars) return Qfalse;
    if (data->flags != data2->flags) return Qfalse;

    return Qtrue;
}

prc[params,...] => obj click to toggle source

Invokes the block, setting the block's parameters to the values in params 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 Kernel.proc, generates an error if the wrong number of parameters are passed to a proc with multiple parameters. For procs created using Proc.new, extra parameters are silently discarded.

Returns the value of the last expression evaluated in the block. See also Proc#yield.

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)

produces:

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(proc, args)
    VALUE proc, args;           /* OK */
{
    return proc_invoke(proc, args, Qundef, 0);
}

arity → fixnum click to toggle source

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 proc with no argument declarations is the same a block declaring || 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

 
               static VALUE
proc_arity(proc)
    VALUE proc;
{
    struct BLOCK *data;
    NODE *list;
    int n;

    Data_Get_Struct(proc, struct BLOCK, data);
    if (data->var == 0) {
        if (data->body && nd_type(data->body) == NODE_IFUNC &&
            data->body->nd_cfnc == bmcall) {
            return method_arity(data->body->nd_tval);
        }
        return INT2FIX(-1);
    }
    if (data->var == (NODE*)1) return INT2FIX(0);
    if (data->var == (NODE*)2) return INT2FIX(0);
    switch (nd_type(data->var)) {
      default:
        return INT2FIX(1);
      case NODE_MASGN:
        list = data->var->nd_head;
        n = 0;
        while (list) {
            n++;
            list = list->nd_next;
        }
        if (data->var->nd_args) return INT2FIX(-n-1);
        return INT2FIX(n);
    }
}

binding => binding click to toggle source

Returns the binding associated with prc. Note that Kernel#eval accepts either a Proc or a Binding object as its second parameter.

def fred(param)
  proc {}
end

b = fred(99)
eval("param", b.binding)   #=> 99
eval("param", b)           #=> 99

 
               static VALUE
proc_binding(proc)
    VALUE proc;
{
    struct BLOCK *orig, *data;
    VALUE bind;

    Data_Get_Struct(proc, struct BLOCK, orig);
    bind = Data_Make_Struct(rb_cBinding,struct BLOCK,blk_mark,blk_free,data);
    MEMCPY(data, orig, struct BLOCK, 1);
    frame_dup(&data->frame);

    if (data->iter) {
        blk_copy_prev(data);
    }
    else {
        data->prev = 0;
    }

    return bind;
}

call(params,...) => obj click to toggle source

Returns the value of the last expression evaluated in the block. See also Proc#yield.

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)

produces:

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(proc, args)
    VALUE proc, args;           /* OK */
{
    return proc_invoke(proc, args, Qundef, 0);
}

clone() click to toggle source

MISSING: documentation

 
               static VALUE
proc_clone(self)
    VALUE self;
{
    struct BLOCK *orig, *data;
    VALUE bind;

    Data_Get_Struct(self, struct BLOCK, orig);
    bind = Data_Make_Struct(rb_obj_class(self),struct BLOCK,blk_mark,blk_free,data);
    CLONESETUP(bind, self);
    blk_dup(data, orig);

    return bind;
}

dup() click to toggle source

 
               static VALUE
proc_dup(self)
    VALUE self;
{
    struct BLOCK *orig, *data;
    VALUE bind;
    int safe = proc_get_safe_level(self);

    Data_Get_Struct(self, struct BLOCK, orig);
    bind = Data_Make_Struct(rb_obj_class(self),struct BLOCK,blk_mark,blk_free,data);
    blk_dup(data, orig);
    if (safe > PROC_TMAX) safe = PROC_TMAX;
    FL_SET(bind, (safe << PROC_TSHIFT) & PROC_TMASK);

    return bind;
}

to_proc → prc click to toggle source

Part of the protocol for converting objects to Proc objects. Instances of class Proc simply return themselves.

 
               static VALUE
proc_to_self(self)
    VALUE self;
{
    return self;
}

to_s => string click to toggle source

Shows the unique identifier for this proc, along with an indication of where the proc was defined.

 
               static VALUE
proc_to_s(self)
    VALUE self;
{
    struct BLOCK *data;
    NODE *node;
    char *cname = rb_obj_classname(self);
    const int w = (sizeof(VALUE) * CHAR_BIT) / 4;
    long len = strlen(cname)+6+w; /* 6:tags 16:addr */
    VALUE str;

    Data_Get_Struct(self, struct BLOCK, data);
    if ((node = data->frame.node) || (node = data->body)) {
        len += strlen(node->nd_file) + 2 + (SIZEOF_LONG*CHAR_BIT-NODE_LSHIFT)/3;
        str = rb_str_new(0, len);
        snprintf(RSTRING(str)->ptr, len+1,
                 "#<%s:0x%.*lx@%s:%d>", cname, w, (VALUE)data->body,
                 node->nd_file, nd_line(node));
    }
    else {
        str = rb_str_new(0, len);
        snprintf(RSTRING(str)->ptr, len+1,
                 "#<%s:0x%.*lx>", cname, w, (VALUE)data->body);
    }
    RSTRING(str)->len = strlen(RSTRING(str)->ptr);
    if (OBJ_TAINTED(self)) OBJ_TAINT(str);

    return str;
}

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