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MLton has a flag, <tt>-show-basis </tt> <em>file</em>, that causes MLton to pretty print to <em>file</em> the basis defined by the input program. For example, if <tt>foo.sml</tt> contains
<pre class=code>
<B><FONT COLOR="#A020F0">fun</FONT></B> f x = x + <B><FONT COLOR="#5F9EA0">1</FONT></B>
</PRE>
<p>
then <tt>mlton -show-basis foo.basis foo.sml</tt> will create <tt>foo.basis</tt> with the following contents.
<pre>val f: int -> int
</pre>If you only want to see the basis and do not wish to compile the program, you can call MLton with <tt>-stop tc</tt>.
</p>
<h2 id="head-f68fa1f6c99a6935aec560696799f2414d893d6f">Displaying signatures</h2>
<p>
When displaying signatures, MLton prefixes types defined in the signature them with <tt>?.</tt> to distinguish them from types defined in the environment. For example,
<pre class=code>
<B><FONT COLOR="#0000FF">signature</FONT></B> SIG =
<B><FONT COLOR="#0000FF">sig</FONT></B>
<B><FONT COLOR="#A020F0">type</FONT></B><B><FONT COLOR="#228B22"> t
</FONT></B><B><FONT COLOR="#A020F0">val</FONT></B> x: t * int -> unit
<B><FONT COLOR="#0000FF">end</FONT></B>
</PRE>
is displayed as
<pre>signature SIG =
sig
type t = ?.t
val x: (?.t * int) -> unit
end
</pre>Notice that <tt>int</tt> occurs without the <tt>?.</tt> prefix.
</p>
<p>
MLton also uses a canonical name for each type in the signature, and that name is used everywhere for that type, no matter what the input signature looked like. For example:
<pre class=code>
<B><FONT COLOR="#0000FF">signature</FONT></B> SIG =
<B><FONT COLOR="#0000FF">sig</FONT></B>
<B><FONT COLOR="#A020F0">type</FONT></B><B><FONT COLOR="#228B22"> t
</FONT></B><B><FONT COLOR="#A020F0">type</FONT></B><B><FONT COLOR="#228B22"> u </FONT></B>=<B><FONT COLOR="#228B22"> t
</FONT></B><B><FONT COLOR="#A020F0">val</FONT></B> x: t
<B><FONT COLOR="#A020F0">val</FONT></B> y: u
<B><FONT COLOR="#0000FF">end</FONT></B>
</PRE>
is displayed as
<pre>signature SIG =
sig
type t = ?.t
type u = ?.t
val x: ?.t
val y: ?.t
end
</pre>
</p>
<p>
Canonical names are always relative to the "top" of the signature, even when used in nested substructures. For example:
<pre class=code>
<B><FONT COLOR="#0000FF">signature</FONT></B> S =
<B><FONT COLOR="#0000FF">sig</FONT></B>
<B><FONT COLOR="#A020F0">type</FONT></B><B><FONT COLOR="#228B22"> t
</FONT></B><B><FONT COLOR="#A020F0">val</FONT></B> w: t
<B><FONT COLOR="#0000FF">structure</FONT></B> U:
<B><FONT COLOR="#0000FF">sig</FONT></B>
<B><FONT COLOR="#A020F0">type</FONT></B><B><FONT COLOR="#228B22"> u
</FONT></B><B><FONT COLOR="#A020F0">val</FONT></B> x: t
<B><FONT COLOR="#A020F0">val</FONT></B> y: u
<B><FONT COLOR="#0000FF">end</FONT></B>
<B><FONT COLOR="#A020F0">val</FONT></B> z: U.u
<B><FONT COLOR="#0000FF">end</FONT></B>
</PRE>
is displayed as
<pre>signature S =
sig
type t = ?.t
val w: ?.t
val z: ?.U.u
structure U:
sig
type u = ?.U.u
val x: ?.t
val y: ?.U.u
end
end
</pre>
</p>
<h2 id="head-c6c2aa845cc7b36e66f2c4aa799b976c96116919">Displaying structures</h2>
<p>
When displaying structures, MLton uses signature constraints wherever possible, combined with <tt>where type</tt> clauses to specify the meanings of the types defined within the signature.
</p>
<pre class=code>
<B><FONT COLOR="#0000FF">signature</FONT></B> SIG =
<B><FONT COLOR="#0000FF">sig</FONT></B>
<B><FONT COLOR="#A020F0">type</FONT></B><B><FONT COLOR="#228B22"> t
</FONT></B><B><FONT COLOR="#A020F0">val</FONT></B> x: t
<B><FONT COLOR="#0000FF">end</FONT></B>
<B><FONT COLOR="#0000FF">structure</FONT></B> S: SIG =
<B><FONT COLOR="#0000FF">struct</FONT></B>
<B><FONT COLOR="#A020F0">type</FONT></B><B><FONT COLOR="#228B22"> t </FONT></B>=<B><FONT COLOR="#228B22"> int
</FONT></B><B><FONT COLOR="#A020F0">val</FONT></B> x = <B><FONT COLOR="#5F9EA0">13</FONT></B>
<B><FONT COLOR="#0000FF">end</FONT></B>
<B><FONT COLOR="#0000FF">structure</FONT></B> S2:> SIG = S
</PRE>
<p>
is displayed as
<pre>structure S: SIG
where type t = int
structure S2: SIG
where type t = S2.t
signature SIG =
sig
type t = ?.t
val x: ?.t
end
</pre>
</p>
</div>
<p>
<hr>
Last edited on 2005-12-02 01:48:03 by <span title="ppp-71-139-183-221.dsl.snfc21.pacbell.net"><a href="StephenWeeks">StephenWeeks</a></span>.
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