language-class            package:methods            R Documentation

_C_l_a_s_s_e_s _t_o _R_e_p_r_e_s_e_n_t _U_n_e_v_a_l_u_a_t_e_d _L_a_n_g_u_a_g_e _O_b_j_e_c_t_s

_D_e_s_c_r_i_p_t_i_o_n:

     The virtual class '"language"' and the specific classes that
     extend it represent unevaluated objects, as produced for example
     by the parser or by functions such as 'quote'.

_U_s_a_g_e:

     ### each of these classes corresponds to an unevaluated object
     ### in the S language.  The class name can appear in method signatures,
     ### and in a few other contexts (such as some calls to as()).

     "("
     "<-"
     "call"
     "for"
     "if"
     "repeat"
     "while"
     "name"
     "{"

     ### Each of the classes above extends the virtual class

     "language"

_O_b_j_e_c_t_s _f_r_o_m _t_h_e _C_l_a_s_s:

     '"language"' is a virtual class; no objects may be created from
     it.

     Objects from the other classes can be generated by a call to
     'new(Class, ...)', where 'Class' is the quoted class name, and the
     ... arguments are either empty or a _single_ object that is from
     this class (or an extension).

_M_e_t_h_o_d_s:

     _c_o_e_r_c_e 'signature(from = "ANY", to = "call")'.  A method exists
          for 'as(object, "call")', calling 'as.call()'. 

