Class: Proc (Ruby 2.3.4)

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    • proc.c

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    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
    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;
    }
                

    Public Instance Methods

    proc === obj → result_of_proc click to toggle source

    Invokes the block with obj as the proc's parameter like #call. It is to allow a proc object to be a target of when clause in a case statement.

     
                   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;
    }
                
    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. 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 #lambda?.

     
                   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;
    }
                
    arity → fixnum click to toggle source

    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_arity(VALUE self)
    {
        int arity = rb_proc_arity(self);
        return INT2FIX(arity);
    }
                
    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
    
     
                   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;
    }
                
    call(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. 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 #lambda?.

     
                   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;
    }
                
    curry → a_proc click to toggle source
    curry(arity) → a_proc

    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_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);
    }
                
    hash → integer click to toggle source

    Returns a hash value corresponding to proc body.

    See also Object#hash.

     
                   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);
    }
                
    inspect() click to toggle source
    Alias for: to_s
    lambda? → true or false click to toggle source

    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
    

    #lambda? is a predicate for the tricks. It returns true if no tricks apply.

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

    ::new is the same as proc.

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

    lambda, proc and ::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.

     
                   VALUE
    rb_proc_lambda_p(VALUE procval)
    {
        rb_proc_t *proc;
        GetProcPtr(procval, proc);
    
        return proc->is_lambda ? Qtrue : Qfalse;
    }
                
    parameters → array click to toggle source

    Returns the parameter information of this proc.

    prc = lambda{|x, y=42, *other|}
    prc.parameters  #=> [[:req, :x], [:opt, :y], [:rest, :other]]
    
     
                   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);
    }
                
    source_location → [String, Fixnum] click to toggle source

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

     
                   VALUE
    rb_proc_location(VALUE self)
    {
        return iseq_location(rb_proc_get_iseq(self, 0));
    }
                
    to_proc → proc 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_proc(VALUE self)
    {
        return self;
    }
                
    to_s → string click to toggle source

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

     
                   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;
    }
                
    Also aliased as: inspect
    yield(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. 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 #lambda?.

     
                   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;
    }