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    <p>As far as I know, you can not do this directly in the sense that there isn't a <code>HoldN</code> attribute. However, below there is a work-around that should be doing what you requested.</p> <hr> <h3>Proposed solution</h3> <p>One simple way is to define an auxiliary function that will do the main work, and your "main" function (the one that will actually be called) as <code>HoldAll</code>, like so:</p> <pre><code>In[437]:= SetAttributes[f, HoldAll]; f[a_, b_, c_] := faux[a, Unevaluated[b], c]; faux[a_, b_, c_] := Hold[a, b, c] In[440]:= f[1^2, 2^2, 3^2] Out[440]= Hold[1, 2^2, 9] </code></pre> <p>You don't have to expose the <code>faux</code> to the top level, can wrap everyting in <code>Module[{faux}, your definitions]</code> instead. </p> <hr> <h3>Automation through meta-programming</h3> <p>This procedure can be automated. Here is a simplistic parser for the function signatures, to extract pattern names (note - it is indeed simplistic):</p> <pre><code>splitHeldSequence[Hold[seq___], f_: Hold] := List @@ Map[f, Hold[seq]]; getFunArguments[Verbatim[HoldPattern][Verbatim[Condition][f_[args___], test_]]] := getFunArguments[HoldPattern[f[args]]]; getFunArguments[Verbatim[HoldPattern][f_[args___]]] := FunArguments[FName[f], FArgs @@ splitHeldSequence[Hold[args]]]; (*This is a simplistic "parser".It may miss some less trivial cases*) getArgumentNames[args__FArgs] := args //. { Verbatim[Pattern][tag_, ___] :&gt; tag, Verbatim[Condition][z_, _] :&gt; z, Verbatim[PatternTest][z_, _] :&gt; z }; </code></pre> <p>Using this, we can write the following custom definition operator:</p> <pre><code>ClearAll[defHoldN]; SetAttributes[defHoldN, HoldFirst]; defHoldN[SetDelayed[f_[args___], rhs_], n_Integer] := Module[{faux}, SetAttributes[f, HoldAll]; With[{heldArgs = MapAt[ Unevaluated, Join @@ getArgumentNames[getFunArguments[HoldPattern[f[args]]][[2]]], n] }, SetDelayed @@ Hold[f[args], faux @@ heldArgs]; faux[args] := rhs]] </code></pre> <p>This will analyze your original definition, extract pattern names, wrap the argument of interest in <code>Unevaluated</code>, introduce local <code>faux</code>, and make a 2-step definition - basically the steps we did manually. We need <code>SetDelayed @@ ..</code> to fool the variable renaming mechanism of <code>With</code>, so that it won't rename our pattern variables on the l.h.s. Example:</p> <pre><code>In[462]:= ClearAll[ff]; defHoldN[ff[x_,y_,z_]:=Hold[x,y,z],2] In[464]:= ?ff Global`ff Attributes[ff]={HoldAll} ff[x_,y_,z_]:=faux$19106@@Hold[x,Unevaluated[y],z] In[465]:= ff[1^2,2^2,3^2] Out[465]= Hold[1,2^2,9] </code></pre> <hr> <h3>Notes</h3> <p>Note that this is trivial to generalize to a list of positions in which you need to hold the arguments. In general, you'd need a better pattern parser, but the simple one above may be a good start. Note also that there will be a bit of run-time overhead induced with this construction, and also that the <code>Module</code>-generated auxiliary functions <code>faux</code> won't be garbage-collected when you <code>Clear</code> or <code>Remove</code> the main ones - you may need to introduce a special destructor for your functions generated with <code>defHoldN</code>. For an alternative take on this problem, see my post in <a href="http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_thread/thread/81da38250f225b95" rel="noreferrer">this</a> thread (the one where I introduced the <code>makeHoldN</code> function).</p>
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    1. USLeonid Shifrin
    1. USLeonid Shifrin
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    1. COI would like to vote twice, once for the solution and once for the ambiguous variable name faux (is it f_auxiliary or the French faux = false/fake?) ;-)
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      1. USSjoerd C. de Vries
    2. CO@Sjoerd Funny - I don't know French at all (something I very much hope to remedy in this life). I must be very gifted in languages then :). Thanks for the upvote.
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      1. USLeonid Shifrin
    3. CO@Leonid, Sjoerd: That thanks could be premature. He said he'd like to vote twice. But he did not say that he voted at all (would that be a faux vote?)
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      1. USDaniel Lichtblau
 

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