doc/guide/localhost/LineDirective

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  26 <h1>LineDirective</h1>
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  31 <div class="paragraph"><p>To aid in the debugging of code produced by program generators such
  32 as <a href="http://www.eecs.harvard.edu/%7Enr/noweb/">Noweb</a>, MLton supports
  33 comments with line directives of the form</p></div>
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  35 <div class="content"><div class="highlight"><pre><span class="cm">(*#line l.c &quot;f&quot;*)</span><span class="w"></span>
  36 </pre></div></div></div>
  37 <div class="paragraph"><p>Here, <em>l</em> and <em>c</em> are sequences of decimal digits and <em>f</em> is the
  38 source file.  The first character of a source file has the position
  39 1.1.  A line directive causes the front end to believe that the
  40 character following the right parenthesis is at the line and column of
  41 the specified file.  A line directive only affects the reporting of
  42 error messages and does not affect program semantics (except for
  43 functions like <span class="monospaced">MLton.Exn.history</span> that report source file positions).
  44 Syntactically invalid line directives are ignored.  To prevent
  45 incompatibilities with SML, the file name may not contain the
  46 character sequence <span class="monospaced">*)</span>.</p></div>
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