<!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <meta name="generator" content="AsciiDoc 8.6.8"> <title>MLBasisExamples</title> <link rel="stylesheet" href="./asciidoc.css" type="text/css"> <link rel="stylesheet" href="./pygments.css" type="text/css"> <script type="text/javascript" src="./asciidoc.js"></script> <script type="text/javascript"> /*<![CDATA[*/ asciidoc.install(); /*]]>*/ </script> <link rel="stylesheet" href="./mlton.css" type="text/css"/> </head> <body class="article"> <div id="banner"> <div id="banner-home"> <a href="./Home">MLton 20130715</a> </div> </div> <div id="header"> <h1>MLBasisExamples</h1> </div> <div id="content"> <div id="preamble"> <div class="sectionbody"> <div class="paragraph"><p>Here are some example uses of <a href="MLBasis">ML Basis</a> files.</p></div> </div> </div> <div class="sect1"> <h2 id="_complete_program">Complete program</h2> <div class="sectionbody"> <div class="paragraph"><p>Suppose your complete program consists of the files <span class="monospaced">file1.sml</span>, …, <span class="monospaced">filen.sml</span>, which depend upon libraries <span class="monospaced">lib1.mlb</span>, …, <span class="monospaced">libm.mlb</span>.</p></div> <div class="listingblock"> <div class="content monospaced"> <pre>(* import libraries *) lib1.mlb ... libm.mlb (* program files *) file1.sml ... filen.sml</pre> </div></div> <div class="paragraph"><p>The bases denoted by <span class="monospaced">lib1.mlb</span>, …, <span class="monospaced">libm.mlb</span> are merged (bindings of names in later bases take precedence over bindings of the same name in earlier bases), producing a basis in which <span class="monospaced">file1.sml</span>, …, <span class="monospaced">filen.sml</span> are elaborated, adding additional bindings to the basis.</p></div> </div> </div> <div class="sect1"> <h2 id="_export_filter">Export filter</h2> <div class="sectionbody"> <div class="paragraph"><p>Suppose you only want to export certain structures, signatures, and functors from a collection of files.</p></div> <div class="listingblock"> <div class="content monospaced"> <pre>local file1.sml ... filen.sml in (* export filter here *) functor F structure S end</pre> </div></div> <div class="paragraph"><p>While <span class="monospaced">file1.sml</span>, …, <span class="monospaced">filen.sml</span> may declare top-level identifiers in addition to <span class="monospaced">F</span> and <span class="monospaced">S</span>, such names are not accessible to programs and libraries that import this <span class="monospaced">.mlb</span>.</p></div> </div> </div> <div class="sect1"> <h2 id="_export_filter_with_renaming">Export filter with renaming</h2> <div class="sectionbody"> <div class="paragraph"><p>Suppose you want an export filter, but want to rename one of the modules.</p></div> <div class="listingblock"> <div class="content monospaced"> <pre>local file1.sml ... filen.sml in (* export filter, with renaming, here *) functor F structure S' = S end</pre> </div></div> <div class="paragraph"><p>Note that <span class="monospaced">functor F</span> is an abbreviation for <span class="monospaced">functor F = F</span>, which simply exports an identifier under the same name.</p></div> </div> </div> <div class="sect1"> <h2 id="_import_filter">Import filter</h2> <div class="sectionbody"> <div class="paragraph"><p>Suppose you only want to import a functor <span class="monospaced">F</span> from one library and a structure <span class="monospaced">S</span> from another library.</p></div> <div class="listingblock"> <div class="content monospaced"> <pre>local lib1.mlb in (* import filter here *) functor F end local lib2.mlb in (* import filter here *) structure S end file1.sml ... filen.sml</pre> </div></div> </div> </div> <div class="sect1"> <h2 id="_import_filter_with_renaming">Import filter with renaming</h2> <div class="sectionbody"> <div class="paragraph"><p>Suppose you want to import a structure <span class="monospaced">S</span> from one library and another structure <span class="monospaced">S</span> from another library.</p></div> <div class="listingblock"> <div class="content monospaced"> <pre>local lib1.mlb in (* import filter, with renaming, here *) structure S1 = S end local lib2.mlb in (* import filter, with renaming, here *) structure S2 = S end file1.sml ... filen.sml</pre> </div></div> </div> </div> <div class="sect1"> <h2 id="_full_basis">Full Basis</h2> <div class="sectionbody"> <div class="paragraph"><p>Since the Modules level of SML is the natural means for organizing program and library components, MLB files provide convenient syntax for renaming Modules level identifiers (in fact, renaming of functor identifiers provides a mechanism that is not available in SML). However, please note that <span class="monospaced">.mlb</span> files elaborate to full bases including top-level types and values (including infix status), in addition to structures, signatures, and functors. For example, suppose you wished to extend the <a href="BasisLibrary">Basis Library</a> with an <span class="monospaced">('a, 'b) either</span> datatype corresponding to a disjoint sum; the type and some operations should be available at the top-level; additionally, a signature and structure provide the complete interface.</p></div> <div class="paragraph"><p>We could use the following files.</p></div> <div class="paragraph"><p><span class="monospaced">either-sigs.sml</span></p></div> <div class="listingblock"> <div class="content"><div class="highlight"><pre><span class="k">signature</span><span class="w"> </span><span class="n">EITHER_GLOBAL</span><span class="w"> </span><span class="p">=</span><span class="w"></span> <span class="w"> </span><span class="k">sig</span><span class="w"></span> <span class="w"> </span><span class="k">datatype</span><span class="w"> </span><span class="p">(</span><span class="n">'a</span><span class="p">,</span><span class="w"> </span><span class="n">'b</span><span class="p">)</span><span class="w"> </span><span class="n">either</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">Left</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="n">'a</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Right</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="n">'b</span><span class="w"></span> <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">&</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">'a</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">'c</span><span class="p">)</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="p">(</span><span class="n">'b</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">'c</span><span class="p">)</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="p">(</span><span class="n">'a</span><span class="p">,</span><span class="w"> </span><span class="n">'b</span><span class="p">)</span><span class="w"> </span><span class="n">either</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">'c</span><span class="w"></span> <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">&&</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">'a</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">'c</span><span class="p">)</span><span class="w"> </span><span class="n">*</span><span class="w"> </span><span class="p">(</span><span class="n">'b</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">'d</span><span class="p">)</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="p">(</span><span class="n">'a</span><span class="p">,</span><span class="w"> </span><span class="n">'b</span><span class="p">)</span><span class="w"> </span><span class="n">either</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="p">(</span><span class="n">'c</span><span class="p">,</span><span class="w"> </span><span class="n">'d</span><span class="p">)</span><span class="w"> </span><span class="n">either</span><span class="w"></span> <span class="w"> </span><span class="k">end</span><span class="w"></span> <span class="k">signature</span><span class="w"> </span><span class="n">EITHER</span><span class="w"> </span><span class="p">=</span><span class="w"></span> <span class="w"> </span><span class="k">sig</span><span class="w"></span> <span class="w"> </span><span class="k">include</span><span class="w"> </span><span class="n">EITHER_GLOBAL</span><span class="w"></span> <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">isLeft</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">'a</span><span class="p">,</span><span class="w"> </span><span class="n">'b</span><span class="p">)</span><span class="w"> </span><span class="n">either</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">bool</span><span class="w"></span> <span class="w"> </span><span class="k">val</span><span class="w"> </span><span class="n">isRight</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="p">(</span><span class="n">'a</span><span class="p">,</span><span class="w"> </span><span class="n">'b</span><span class="p">)</span><span class="w"> </span><span class="n">either</span><span class="w"> </span><span class="p">-></span><span class="w"> </span><span class="n">bool</span><span class="w"></span> <span class="w"> </span><span class="p">...</span><span class="w"></span> <span class="w"> </span><span class="k">end</span><span class="w"></span> </pre></div></div></div> <div class="paragraph"><p><span class="monospaced">either-strs.sml</span></p></div> <div class="listingblock"> <div class="content"><div class="highlight"><pre><span class="k">structure</span><span class="w"> </span><span class="n">Either</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">EITHER</span><span class="w"> </span><span class="p">=</span><span class="w"></span> <span class="w"> </span><span class="k">struct</span><span class="w"></span> <span class="w"> </span><span class="k">datatype</span><span class="w"> </span><span class="p">(</span><span class="n">'a</span><span class="p">,</span><span class="w"> </span><span class="n">'b</span><span class="p">)</span><span class="w"> </span><span class="n">either</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">Left</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="n">'a</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Right</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="n">'b</span><span class="w"></span> <span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="n">&</span><span class="w"> </span><span class="n">g</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="k">fn</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="p">=></span><span class="w"></span> <span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="k">of</span><span class="w"> </span><span class="n">Left</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="p">|</span><span class="w"> </span><span class="n">Right</span><span class="w"> </span><span class="n">z</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">g</span><span class="w"> </span><span class="n">z</span><span class="w"></span> <span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="n">&&</span><span class="w"> </span><span class="n">g</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="p">(</span><span class="n">Left</span><span class="w"> </span><span class="n">o</span><span class="w"> </span><span class="n">f</span><span class="p">)</span><span class="w"> </span><span class="n">&</span><span class="w"> </span><span class="p">(</span><span class="n">Right</span><span class="w"> </span><span class="n">o</span><span class="w"> </span><span class="n">g</span><span class="p">)</span><span class="w"></span> <span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">isLeft</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="p">((</span><span class="k">fn</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">true</span><span class="p">)</span><span class="w"> </span><span class="n">&</span><span class="w"> </span><span class="p">(</span><span class="k">fn</span><span class="w"> </span><span class="p">_</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="n">false</span><span class="p">))</span><span class="w"> </span><span class="n">x</span><span class="w"></span> <span class="w"> </span><span class="k">fun</span><span class="w"> </span><span class="n">isRight</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="p">(</span><span class="n">not</span><span class="w"> </span><span class="n">o</span><span class="w"> </span><span class="n">isLeft</span><span class="p">)</span><span class="w"> </span><span class="n">x</span><span class="w"></span> <span class="w"> </span><span class="p">...</span><span class="w"></span> <span class="w"> </span><span class="k">end</span><span class="w"></span> <span class="k">structure</span><span class="w"> </span><span class="n">EitherGlobal</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">EITHER_GLOBAL</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="n">Either</span><span class="w"></span> </pre></div></div></div> <div class="paragraph"><p><span class="monospaced">either-infixes.sml</span></p></div> <div class="listingblock"> <div class="content"><div class="highlight"><pre><span class="k">infixr</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="n">&</span><span class="w"> </span><span class="n">&&</span><span class="w"></span> </pre></div></div></div> <div class="paragraph"><p><span class="monospaced">either-open.sml</span></p></div> <div class="listingblock"> <div class="content"><div class="highlight"><pre><span class="k">open</span><span class="w"> </span><span class="n">EitherGlobal</span><span class="w"></span> </pre></div></div></div> <div class="paragraph"><p><span class="monospaced">either.mlb</span></p></div> <div class="listingblock"> <div class="content monospaced"> <pre>either-infixes.sml local (* import Basis Library *) $(SML_LIB)/basis/basis.mlb either-sigs.sml either-strs.sml in signature EITHER structure Either either-open.sml end</pre> </div></div> <div class="paragraph"><p>A client that imports <span class="monospaced">either.mlb</span> will have access to neither <span class="monospaced">EITHER_GLOBAL</span> nor <span class="monospaced">EitherGlobal</span>, but will have access to the type <span class="monospaced">either</span> and the values <span class="monospaced">&</span> and <span class="monospaced">&&</span> (with infix status) in the top-level environment. Note that <span class="monospaced">either-infixes.sml</span> is outside the scope of the local, because we want the infixes available in the implementation of the library and to clients of the library.</p></div> </div> </div> </div> <div id="footnotes"><hr></div> <div id="footer"> <div id="footer-text"> </div> <div id="footer-badges"> </div> </div> </body> </html>