http://dev.clojure.org/jira This file is an XML representation of an issue en-us 4.4 649 25-07-2011 http://dev.clojure.org/jira/browse/CLJ-1145 Clojure <p>At times, as the artifact of repl experimentation or a refactoring in progress, one wants to eval a threaded form with 1 or (less likely) 0 arguments.</p> <p><tt>(-&gt; 42) ; fine</tt><br/> <tt>(-<del>&gt;&gt; 42) ; throws "ArityException Wrong number of args (1) passed to: core$</del>-GT".</tt></p> <p><tt>(-&gt;) ; throws "ArityException Wrong number of args (0) passed to: core$" (sic)</tt><br/> <tt>(-<del>&gt;&gt;) ; throws "ArityException Wrong number of args (0) passed to: core$</del>-GT".</tt></p> <p>Apologies for the text rendering (how to cite code?).</p> CLJ-1145

thread-last can't accept 0 or 1 forms, thread-first can't accept 0 forms

Defect Minor Closed Duplicate Unassigned Víctor M. Valenzuela Sat, 12 Jan 2013 14:06:42 -0600 Sun, 13 Jan 2013 09:40:39 -0600 Sun, 13 Jan 2013 09:40:39 -0600 0 0 <p>Is this a duplicate with <a href="http://dev.clojure.org/jira/browse/CLJ-1086" title="Support arity-1 for -&gt;&gt;">CLJ-1086</a>, <a href="http://dev.clojure.org/jira/browse/CLJ-1121" title="-&gt; and -&gt;&gt; have unexpected behavior when combined with unusual macros">CLJ-1121</a>, or the combination of those two?</p> <p>If arity 0 is a new aspect of this ticket, what would you expect the arity 0 versions to be transformed into? nil?</p> <p>Surely a duplicate - but Jira's search couldn't find those! (used "-&gt;", "thread-last" etc as search queries).</p> <p>While fairly unlikely to use / noisy to implement, the thing about feeding 0-arities to the threading macros is that they throw in exchange an unrelated exception rather than e.g. "ArityException Wrong number of args (0) passed to: core$-&gt;".</p> <p>Don't know if this is simply how macros (can) work, but it called my attention.</p> <p>Feel free to close my issue.</p> <p>I will go ahead and close this case as a duplicate. FYI, below is the behavior if the <a href="http://dev.clojure.org/jira/browse/CLJ-1121" title="-&gt; and -&gt;&gt; have unexpected behavior when combined with unusual macros">CLJ-1121</a> patch <a href="http://dev.clojure.org/jira/browse/CLJ-1121" title="-&gt; and -&gt;&gt; have unexpected behavior when combined with unusual macros">CLJ-1121</a>-v002.patch and the <a href="http://dev.clojure.org/jira/browse/CLJ-1083" title="Incorrect ArityException message for function names containing -&gt;">CLJ-1083</a> patch <a href="http://dev.clojure.org/jira/browse/CLJ-1083" title="Incorrect ArityException message for function names containing -&gt;">CLJ-1083</a>-attachments/better-throw-arity-messages.diff are both applied (the second one improves the error message in the 0-arity case):</p> <p>Clojure 1.5.0-master-SNAPSHOT<br/> user=&gt; (-&gt;)<br/> ArityException Wrong number of args (0) passed to: core/-&gt; clojure.lang.Compiler.macroexpand1 (Compiler.java:6472)<br/> user=&gt; (-&gt; 5)<br/> 5<br/> user=&gt; (-&gt;&gt;)<br/> ArityException Wrong number of args (0) passed to: core/-&gt;&gt; clojure.lang.Compiler.macroexpand1 (Compiler.java:6472)<br/> user=&gt; (-&gt;&gt; 5)<br/> 5</p> <p>The issue of a poor error message with 0-arity threading macros is improved by the patch attached to ticket <a href="http://dev.clojure.org/jira/browse/CLJ-1083" title="Incorrect ArityException message for function names containing -&gt;">CLJ-1083</a>, and adding handling of the 1-arity case is improved by the patch attached to ticket <a href="http://dev.clojure.org/jira/browse/CLJ-1121" title="-&gt; and -&gt;&gt; have unexpected behavior when combined with unusual macros">CLJ-1121</a>.</p> Global Rank