Proc

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

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

          
        

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_arity(VALUE self)
{
    int arity = rb_proc_arity(self);
    return INT2FIX(arity);
}

          
        

Returns the number of mandatory arguments. 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, returns -n-1, where n is the number of mandatory arguments, with the exception for blocks that are not lambdas and have only a finite number of optional arguments; in this latter case, returns n. Keywords arguments will considered as a single additional argument, that argument being mandatory if any keyword argument is mandatory. A proc with no argument declarations is the same as a block declaring || as its arguments.

proc {}.arity                  #=>  0
proc { || }.arity              #=>  0
proc { |a| }.arity             #=>  1
proc { |a, b| }.arity          #=>  2
proc { |a, b, c| }.arity       #=>  3
proc { |*a| }.arity            #=> -1
proc { |a, *b| }.arity         #=> -2
proc { |a, *b, c| }.arity      #=> -3
proc { |x:, y:, z:0| }.arity   #=>  1
proc { |*a, x:, y:0| }.arity   #=> -2

proc   { |x=0| }.arity         #=>  0
lambda { |x=0| }.arity         #=> -1
proc   { |x=0, y| }.arity      #=>  1
lambda { |x=0, y| }.arity      #=> -2
proc   { |x=0, y=0| }.arity    #=>  0
lambda { |x=0, y=0| }.arity    #=> -1
proc   { |x, y=0| }.arity      #=>  1
lambda { |x, y=0| }.arity      #=> -2
proc   { |(x, y), z=0| }.arity #=>  1
lambda { |(x, y), z=0| }.arity #=> -2
proc   { |a, x:0, y:0| }.arity #=>  1
lambda { |a, x:0, y:0| }.arity #=> -2

          
            
static VALUE
proc_binding(VALUE self)
{
    VALUE bindval, envval;
    const rb_proc_t *proc;
    const rb_iseq_t *iseq;
    rb_binding_t *bind;

    GetProcPtr(self, proc);
    envval = rb_vm_proc_envval(proc);
    iseq = proc->block.iseq;
    if (SYMBOL_P(iseq)) goto error;
    if (RUBY_VM_IFUNC_P(iseq)) {
        struct vm_ifunc *ifunc = (struct vm_ifunc *)iseq;
        if (IS_METHOD_PROC_IFUNC(ifunc)) {
            VALUE method = (VALUE)ifunc->data;
            envval = env_clone(envval, method_receiver(method), method_cref(method));
            iseq = rb_method_iseq(method);
        }
        else {
          error:
            rb_raise(rb_eArgError, "Can't create Binding from C level Proc");
        }
    }

    bindval = rb_binding_alloc(rb_cBinding);
    GetBindingPtr(bindval, bind);
    bind->env = envval;

    if (iseq) {
        rb_iseq_check(iseq);
        bind->path = iseq->body->location.path;
        bind->first_lineno = FIX2INT(rb_iseq_first_lineno(iseq));
    }
    else {
        bind->path = Qnil;
        bind->first_lineno = 0;
    }

    return bindval;
}

          
        

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

          
            
0
static VALUE
proc_call(int argc, VALUE *argv, VALUE procval)
{
    VALUE vret;
    const rb_block_t *blockptr = 0;
    const rb_iseq_t *iseq;
    rb_proc_t *proc;
    VALUE passed_procval;
    GetProcPtr(procval, proc);

    iseq = proc->block.iseq;
    if (RUBY_VM_IFUNC_P(iseq) || iseq->body->param.flags.has_block) {
        if (rb_block_given_p()) {
            rb_proc_t *passed_proc;
            passed_procval = rb_block_proc();
            GetProcPtr(passed_procval, passed_proc);
            blockptr = &passed_proc->block;
        }
    }

    vret = rb_vm_invoke_proc(GET_THREAD(), proc, argc, argv, blockptr);
    RB_GC_GUARD(procval);
    RB_GC_GUARD(passed_procval);
    return vret;
}

          
        

Invokes the block, setting the block’s parameters to the values in params using something close to method calling semantics. Returns the value of the last expression evaluated in the block.

a_proc = Proc.new {|scalar, *values| values.map {|value| value*scalar } }
a_proc.call(9, 1, 2, 3)    #=> [9, 18, 27]
a_proc[9, 1, 2, 3]         #=> [9, 18, 27]
a_proc.(9, 1, 2, 3)        #=> [9, 18, 27]
a_proc.yield(9, 1, 2, 3)   #=> [9, 18, 27]

Note that prc.() invokes prc.call() with the parameters given. It’s syntactic sugar to hide “call”.

For procs created using lambda or ->() an error is generated if the wrong number of parameters are passed to the proc. For procs created using Proc.new or Kernel.proc, extra parameters are silently discarded and missing parameters are set to nil.

a_proc = proc {|a,b| [a,b] }
a_proc.call(1)   #=> [1, nil]

a_proc = lambda {|a,b| [a,b] }
a_proc.call(1)   # ArgumentError: wrong number of arguments (given 1, expected 2)

See also Proc#lambda?.

          
            
static VALUE
proc_curry(int argc, const VALUE *argv, VALUE self)
{
    int sarity, max_arity, min_arity = rb_proc_min_max_arity(self, &max_arity);
    VALUE arity;

    rb_scan_args(argc, argv, "01", &arity);
    if (NIL_P(arity)) {
        arity = INT2FIX(min_arity);
    }
    else {
        sarity = FIX2INT(arity);
        if (rb_proc_lambda_p(self)) {
            rb_check_arity(sarity, min_arity, max_arity);
        }
    }

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

          
        

Returns a curried proc. If the optional arity 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 (given 4, expected 3)
p b.curry(5)                 #=> wrong number of arguments (given 5, expected 3)
p b.curry(1)                 #=> wrong number of arguments (given 1, expected 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 (given 1, expected 3)

b = proc { :foo }
p b.curry[]                  #=> :foo

          
            
static VALUE
proc_hash(VALUE self)
{
    st_index_t hash;
    hash = rb_hash_start(0);
    hash = rb_hash_proc(hash, self);
    hash = rb_hash_end(hash);
    return LONG2FIX(hash);
}

          
        

Returns a hash value corresponding to proc body.

See also Object#hash.

          
            
VALUE
rb_proc_lambda_p(VALUE procval)
{
    rb_proc_t *proc;
    GetProcPtr(procval, proc);

    return proc->is_lambda ? Qtrue : Qfalse;
}

          
        

Returns true for a Proc object for which argument handling is rigid. Such procs are typically generated by lambda.

A Proc object generated by proc ignores extra arguments.

proc {|a,b| [a,b] }.call(1,2,3)    #=> [1,2]

It provides nil for missing arguments.

proc {|a,b| [a,b] }.call(1)        #=> [1,nil]

It expands a 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 apply.

lambda {}.lambda?            #=> true
proc {}.lambda?              #=> false

Proc.new is the same as proc.

Proc.new {}.lambda?          #=> false

lambda, proc and Proc.new preserve 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 the same as method definition. The defined method has no tricks.

class C
  define_method(:d) {}
end
C.new.d(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 for 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 insures that methods never have tricks and makes it easy to have wrappers to define methods that behave as usual.

class C
  def self.def2(name, &body)
    define_method(name, &body)
  end

  def2(:f) {}
end
C.new.f(1,2)       #=> ArgumentError

The wrapper def2 defines a method which has no tricks.

          
            
static VALUE
rb_proc_parameters(VALUE self)
{
    int is_proc;
    const rb_iseq_t *iseq = rb_proc_get_iseq(self, &is_proc);
    if (!iseq) {
        return unnamed_parameters(rb_proc_arity(self));
    }
    return rb_iseq_parameters(iseq, is_proc);
}

          
        

Returns the parameter information of this proc.

prc = lambda{|x, y=42, *other|}
prc.parameters  #=> [[:req, :x], [:opt, :y], [:rest, :other]]

          
            
VALUE
rb_proc_location(VALUE self)
{
    return iseq_location(rb_proc_get_iseq(self, 0));
}

          
        

Returns the Ruby source filename and line number containing this proc or nil if this proc was not defined in Ruby (i.e. native).

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

          
        

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

          
            
static VALUE
proc_to_s(VALUE self)
{
    VALUE str = 0;
    rb_proc_t *proc;
    const char *cname = rb_obj_classname(self);
    const 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) && rb_iseq_check(iseq)) {
        int first_lineno = 0;

        if (iseq->body->line_info_table) {
            first_lineno = FIX2INT(rb_iseq_first_lineno(iseq));
        }
        str = rb_sprintf("#<%s:%p@%"PRIsVALUE":%d%s>", cname, (void *)self,
                         iseq->body->location.path, first_lineno, is_lambda);
    }
    else if (SYMBOL_P(iseq)) {
        str = rb_sprintf("#<%s:%p(&%+"PRIsVALUE")%s>", cname, (void *)self,
                         (VALUE)iseq, is_lambda);
    }
    else {
        str = rb_sprintf("#<%s:%p%s>", cname, (void *)proc->block.iseq,
                         is_lambda);
    }

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

          
        

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