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#line directives

To aid in the debugging of code produced by program genenerators such as Noweb, MLton supports comments with #line directives of the form (*#line line.col "file"*). Here, line and col are sequences of decimal digits and file is the source file. A #line directive causes the front end to believe that the character following the right parenthesis is at the line and column of the specified file. A #line directive only affects the reporting of error messages and does not affect program semantics (except for functions like MLton.Exn.history which report source file positions). Syntactically invalid #line directives are ignored.