Question

I have the following Clojure code and I’m not sure why it’s not working:

(defn match (x y &optional binds)   (cond    ((eql x y) (values binds t))    ((assoc x binds) (match (binding x binds) y binds))    ((assoc y binds) (match x (binding y binds) binds))    ((var? x) (values (cons (cons x y) binds) t))    ((var? y) (values (cons (cons y x) binds) t))    (t     (when (and (consp x) (consp y))       (multiple-value-bind (b2 yes)                            (match (car x) (car y) binds)         (and yes (match (cdr x) (cdr y) b2))))))) 

(The code is translated from Paul Graham’s ANSI Common Lisp book.)

When I run it, I get the following error:

java.lang.IllegalArgumentException: Don't know how to create ISeq from: Symbol clojure.lang.Compiler$CompilerException: NO_SOURCE_FILE:2: java.lang.RuntimeException: java.lang.IllegalArgumentException: Don't know how to create ISeq from: Symbol         at clojure.lang.Compiler.analyze(Compiler.java:3713)         at clojure.lang.Compiler.analyzeSeq(Compiler.java:3848)         at clojure.lang.Compiler.analyze(Compiler.java:3698)         at clojure.lang.Compiler.access$200(Compiler.java:37)         at clojure.lang.Compiler$DefExpr$Parser.parse(Compiler.java:343)         at clojure.lang.Compiler.analyzeSeq(Compiler.java:3858)         at clojure.lang.Compiler.analyze(Compiler.java:3698)         at clojure.lang.Compiler.analyzeSeq(Compiler.java:3848)         at clojure.lang.Compiler.analyze(Compiler.java:3698)         at clojure.lang.Compiler.analyze(Compiler.java:3671)         at clojure.lang.Compiler.eval(Compiler.java:3895)         at clojure.lang.Repl.main(Repl.java:75)         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)         at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)         at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)         at java.lang.reflect.Method.invoke(Unknown Source)         at jline.ConsoleRunner.main(ConsoleRunner.java:69) Caused by: java.lang.RuntimeException: java.lang.RuntimeException: java.lang.IllegalArgumentException: Don't know how to create ISeq from: Symbol         at clojure.lang.LazyCons.rest(LazyCons.java:64)         at clojure.lang.ASeq.count(ASeq.java:85)         at clojure.lang.RT.count(RT.java:486)         at clojure.lang.Cons.count(Cons.java:41)         at clojure.lang.Compiler.analyze(Compiler.java:3695)         ... 16 more Caused by: java.lang.RuntimeException: java.lang.IllegalArgumentException: Don't know how to create ISeq from: Symbol         at clojure.lang.LazyCons.first(LazyCons.java:44)         at clojure.lang.LazyCons.rest(LazyCons.java:59)         ... 20 more Caused by: java.lang.IllegalArgumentException: Don't know how to create ISeq from: Symbol         at clojure.lang.RT.seqFrom(RT.java:465)         at clojure.lang.RT.seq(RT.java:448)         at clojure.seq__28.invoke(boot.clj:92)         at clojure.every_QMARK___596.invoke(boot.clj:1180)         at clojure.fn__1147$psig__1149.invoke(boot.clj:2155)         at clojure.map__602$fn__605.invoke(boot.clj:1214)         at clojure.lang.LazyCons.first(LazyCons.java:40)         ... 21 more 

What am I doing wrong here?

Answer 1

The problem is that I’m using parentheses (‘(‘ and ‘)’), rather than square brackets (‘[‘ and ‘]’), for the arguments list.

It should start out like this:

(defn match [x y &optional binds] 

(I found the answer in Programming Clojure by Stuart Halloway.)