doc/guide/src/LineDirective.adoc

   1 LineDirective
   2 =============
   3
   4 To aid in the debugging of code produced by program generators such
   5 as http://www.eecs.harvard.edu/%7Enr/noweb/[Noweb], MLton supports
   6 comments with line directives of the form
   7 [source,sml]
   8 ----
   9 (*#line l.c "f"*)
  10 ----
  11 Here, _l_ and _c_ are sequences of decimal digits and _f_ is the
  12 source file.  The first character of a source file has the position
  13 1.1.  A line directive causes the front end to believe that the
  14 character following the right parenthesis is at the line and column of
  15 the specified file.  A line directive only affects the reporting of
  16 error messages and does not affect program semantics (except for
  17 functions like `MLton.Exn.history` that report source file positions).
  18 Syntactically invalid line directives are ignored.  To prevent
  19 incompatibilities with SML, the file name may not contain the
  20 character sequence `*)`.