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<p class="MsoNormal">SpecificationPart is made up of lists of other nodes. When the specification-part of a program is absent, it is represented by a SpecificationPart containing only empty lists. So there is no need to make it optional. The same applies to
ExecutionPart.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Tim<o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">flang-dev <flang-dev-bounces@lists.llvm.org> on behalf of Rajesh K Singh via flang-dev <flang-dev@lists.llvm.org><br>
<b>Reply-To: </b>Rajesh K Singh <rajeshsingh.h606@gmail.com><br>
<b>Date: </b>Friday, October 25, 2019 at 2:05 AM<br>
<b>To: </b>"flang-dev@lists.llvm.org" <flang-dev@lists.llvm.org><br>
<b>Subject: </b>[flang-dev] Regarding main program structure<o:p></o:p></span></p>
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<p class="MsoNormal">Hello,<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">According to specification R1401, a Fortran main program *must* have an “end statement” whereas other parts are optional.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">// R1401 main-program -><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">// [program-stmt] [specification-part] [execution-part]<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">// [internal-subprogram-part] end-program-stmt<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thus, the below case.f90 is a legitimate fortran program:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">[user@localhost ~/F18]$ cat -n case.f90<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> 1 end !only end-program-stmt is specified.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">[user@localhost ~/F18]$<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">The implementation of MainProgram structure (“lib/parser/parse-tree.h”) shows that only “ProgramStmt” and “InternalSubprogramPart” are optional.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">struct MainProgram {<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> TUPLE_CLASS_BOILERPLATE(MainProgram);<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> std::tuple<std::optional<Statement<ProgramStmt>>, SpecificationPart,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> ExecutionPart, std::optional<InternalSubprogramPart>,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> Statement<EndProgramStmt>><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> t;<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">};<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Why “SpecificationPart” and “ExecutionPart” are not implemented as optional (std::optional), while these are optional similar to “ProgramStmt” and “InternalSubprogramPart”?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thanks in anticipation.<o:p></o:p></p>
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