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<html>
<head><title>CW.html -- ACL2 Version 3.1</title></head>
<body text=#000000 bgcolor="#FFFFFF">
<h2>CW</h2>print to the comment window
<pre>Major Section: <a href="PROGRAMMING.html">PROGRAMMING</a>
</pre><p>
Example:
<pre>
(cw "The goal is ~p0 and the alist is ~x1.~%"
(untranslate term t nil)
unify-subst)
</pre>
Logically, this expression is equivalent to <code>nil</code>. However, it has
the effect of first printing to the so-called ``comment window'' the
<code><a href="FMT.html">fmt</a></code> string as indicated. Thus, <code>cw</code> is like <code>fmt</code> (see <a href="FMT.html">fmt</a>) except
in three important ways. First, it is a <code>:</code><code><a href="LOGIC.html">logic</a></code> mode function.
Second, it neither takes nor returns the ACL2 <code><a href="STATE.html">state</a></code>; logically <code>cw</code>
simply returns <code>nil</code>, although it prints to a <em>comment window</em> that just
happens to share the terminal screen with the standard character
output <code><a href="_star_STANDARD-CO_star_.html">*standard-co*</a></code>. Third, its <code>fmt</code> args are positional
references, so that for example
<pre>
(cw "Answers: ~p0 and ~p1" ans1 ans2)
</pre>
prints in the same manner as:
<pre>
(fmt "Answers: ~p0 and ~p1"
(list (cons #\0 ans1) (cons #\1 ans2))
*standard-co* state nil)
</pre>
Typically, calls of <code>cw</code> are embedded in <code><a href="PROG2$.html">prog2$</a></code> forms, e.g.,
<pre>
(prog2$ (cw ...)
(mv a b c))
</pre>
which has the side-effect of printing to the comment window and
logically returning <code>(mv a b c)</code>.
<p>
<pre>
General Form:
(cw fmt-string arg1 arg2 ... argn)
</pre>
where n is between 0 and 9 (inclusive).
The macro uses <code><a href="FMT-TO-COMMENT-WINDOW.html">fmt-to-comment-window</a></code>, passing it the column <code>0</code> and
evisc-tuple <code>nil</code>, after assembling the appropriate alist binding the
<code><a href="FMT.html">fmt</a></code> vars #\0 through #\9; see <a href="FMT.html">fmt</a>. If you want
<pre>
(a) more than 10 vars,
(b) vars other than the digit chars,
(c) a different column, or
(d) a different evisc-tuple,
</pre>
then call <code><a href="FMT-TO-COMMENT-WINDOW.html">fmt-to-comment-window</a></code> instead.
<br><br><br><a href="acl2-doc.html"><img src="llogo.gif"></a> <a href="acl2-doc-index.html"><img src="index.gif"></a>
</body>
</html>
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