by Jon Ripley, Richard Russell, January 2012

The FN_linenumber(!384) function returns the line number of the currently executing line of code as demonstrated below.

  12345 PRINT FN_linenumber(!384)
        END
 
        DEF FN_linenumber(E%)
        LOCAL p%% : p%% = PAGE
        WHILE ?p%% AND p%% + ?p%% < (E% + PAGE - !340) p%% += ?p%% : ENDWHILE
        = (p%%?2*256+p%%?1)

Always pass !384 as the parameter to FN_linenumber, this interpreter internal variable is the pointer to (or within) currently-executing statement.