4.4BSD/usr/share/man/cat3/isinf.0

ISINF(3)                    BSD Programmer's Manual                   ISINF(3)

NNAAMMEE
     iissiinnff, iissnnaann - test for infinity or not-a-number (_N_a_N)

SSYYNNOOPPSSIISS
     _i_n_t
     iissiinnff(_d_o_u_b_l_e);

     _i_n_t
     iissnnaann(_d_o_u_b_l_e);

DDEESSCCRRIIPPTTIIOONN
     The iissnniinnff() function returns 1 if the number is ``infinity'', otherwise
     0.

     The iissnnaann() function returns 1 if the number is ``_N_a_N'', otherwise 0.

SSEEEE AALLSSOO
     math(3)

     _I_E_E_E _S_t_a_n_d_a_r_d _f_o_r _B_i_n_a_r_y _F_l_o_a_t_i_n_g_-_P_o_i_n_t _A_r_i_t_h_m_e_t_i_c, Std 754-1985, ANSI.

BBUUGGSS
     Neither the VAX nor the Tahoe floating point have distinguished values
     for either infinity or not-a-number.  These routines always return 0 on
     those architectures.

4.4BSD                           June 4, 1993                                1