On Sat, Jan 3, 2009 at 10:47 AM, Olov Lassus <olov.las...@gmail.com> wrote:
>
> The for macro is only valid for a vector of even size. Throwing an
> exception when this isn't the case would have helped the original
> poster
The 'let' macro already has a similar check.
Attached is a patch that adds even-ness and related assertions to a
bunch of core macros. It introduces a private macro 'assert-args'
that allows these checks without too much impact on the verbosity and
readability of the code.
--Chouser
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commit b809b1787d7572a737810bfb1147a382b3edd8e8
Author: Chouser <chou...@n01se.net>
Date: Sat Jan 3 11:26:57 2009 -0500
Add assertions about binding forms to many macros.
diff --git a/src/clj/clojure/core.clj b/src/clj/clojure/core.clj
index 235c5f7..3fcc6b4 100644
--- a/src/clj/clojure/core.clj
+++ b/src/clj/clojure/core.clj
@@ -358,7 +358,10 @@
[& clauses]
(when clauses
(list 'if (first clauses)
- (second clauses)
+ (if (rest clauses)
+ (second clauses)
+ (throw (IllegalArgumentException.
+ "cond requires an even number of forms")))
(cons 'clojure.core/cond (rest (rest clauses))))))
(defn spread
@@ -1021,6 +1024,14 @@
;;;;;;;;; var stuff
+(defmacro #^{:private true} assert-args [fnname & pairs]
+ `(do (when-not ~(first pairs)
+ (throw (IllegalArgumentException.
+ ~(str fnname " requires " (second pairs)))))
+ ~(let [more (rrest pairs)]
+ (when more
+ (list* `assert-args fnname more)))))
+
(defmacro binding
"binding => var-symbol init-expr
@@ -1028,6 +1039,9 @@
supplied initial values, executes the exprs in an implicit do, then
re-establishes the bindings that existed before."
[bindings & body]
+ (assert-args binding
+ (vector? bindings) "a vector for its binding"
+ (even? (count bindings)) "an even number of forms in binding vector")
(let [var-ize (fn [var-vals]
(loop [ret [] vvs (seq var-vals)]
(if vvs
@@ -1570,6 +1584,9 @@
bindings and filtering as provided by \"for\". Does not retain
the head of the sequence. Returns nil."
[seq-exprs & body]
+ (assert-args doseq
+ (vector? seq-exprs) "a vector for its binding"
+ (even? (count seq-exprs)) "an even number of forms in binding vector")
(let [groups (reduce (fn [groups p]
(if (keyword? (first p))
(conj (pop groups) (apply assoc (peek groups) p))
@@ -1654,16 +1671,16 @@
Repeatedly executes body (presumably for side-effects) with name
bound to integers from 0 through n-1."
[bindings & body]
- (if (vector? bindings)
- (let [i (first bindings)
- n (second bindings)]
- `(let [n# (int ~n)]
- (loop [~i (int 0)]
- (when (< ~i n#)
- ~...@body
- (recur (unchecked-inc ~i))))))
- (throw (IllegalArgumentException.
- "dotimes now requires a vector for its binding"))))
+ (assert-args dotimes
+ (vector? bindings) "a vector for its binding"
+ (even? (count bindings)) "exactly 2 forms in binding vector")
+ (let [i (first bindings)
+ n (second bindings)]
+ `(let [n# (int ~n)]
+ (loop [~i (int 0)]
+ (when (< ~i n#)
+ ~...@body
+ (recur (unchecked-inc ~i)))))))
(defn import
"import-list => (package-symbol class-name-symbols*)
@@ -1915,18 +1932,18 @@
of the inits, and a finally clause that calls (.close name) on each
name in reverse order."
[bindings & body]
- (if (vector? bindings)
- (cond
- (= (count bindings) 0) `(do ~...@body)
- (symbol? (bindings 0)) `(let ~(subvec bindings 0 2)
- (try
- (with-open ~(subvec bindings 2) ~...@body)
- (finally
- (. ~(bindings 0) close))))
- :else (throw (IllegalArgumentException.
- "with-open only allows Symbols in bindings")))
- (throw (IllegalArgumentException.
- "with-open now requires a vector for its binding"))))
+ (assert-args with-open
+ (vector? bindings) "a vector for its binding"
+ (even? (count bindings)) "an even number of forms in binding vector")
+ (cond
+ (= (count bindings) 0) `(do ~...@body)
+ (symbol? (bindings 0)) `(let ~(subvec bindings 0 2)
+ (try
+ (with-open ~(subvec bindings 2) ~...@body)
+ (finally
+ (. ~(bindings 0) close))))
+ :else (throw (IllegalArgumentException.
+ "with-open only allows Symbols in bindings"))))
(defmacro doto
"Evaluates x then calls all of the methods and functions with the
@@ -2313,6 +2330,9 @@
to the var objects themselves, and must be accessed with var-get and
var-set"
[name-vals-vec & body]
+ (assert-args with-local-vars
+ (vector? name-vals-vec) "a vector for its binding"
+ (even? (count name-vals-vec)) "an even number of forms in binding vector")
`(let [~@(interleave (take-nth 2 name-vals-vec)
(repeat '(. clojure.lang.Var (create))))]
(. clojure.lang.Var (pushThreadBindings (hash-map ~...@name-vals-vec)))
@@ -2408,8 +2428,9 @@
the binding-forms are bound to their respective init-exprs or parts
therein."
[bindings & body]
- (when (odd? (count bindings))
- (throw (Exception. "Odd number of elements in let bindings")))
+ (assert-args let
+ (vector? bindings) "a vector for its binding"
+ (even? (count bindings)) "an even number of forms in binding vector")
`(let* ~(destructure bindings) ~...@body))
;redefine fn with destructuring
@@ -2455,6 +2476,9 @@
the binding-forms are bound to their respective init-exprs or parts
therein. Acts as a recur target."
[bindings & body]
+ (assert-args loop
+ (vector? bindings) "a vector for its binding"
+ (even? (count bindings)) "an even number of forms in binding vector")
(let [db (destructure bindings)]
(if (= db bindings)
`(loop* ~bindings ~...@body)
@@ -2476,13 +2500,13 @@
Same as (when (seq xs) (let [x (first xs)] body))"
[bindings & body]
- (if (vector? bindings)
- (let [[x xs] bindings]
- `(when (seq ~xs)
- (let [~x (first ~xs)]
- ~...@body)))
- (throw (IllegalArgumentException.
- "when-first now requires a vector for its binding"))))
+ (assert-args when-first
+ (vector? bindings) "a vector for its binding"
+ (even? (count bindings)) "exactly 2 forms in binding vector")
+ (let [[x xs] bindings]
+ `(when (seq ~xs)
+ (let [~x (first ~xs)]
+ ~...@body))))
(defmacro lazy-cat
"Expands to code which yields a lazy sequence of the concatenation
@@ -2506,6 +2530,9 @@
(take 100 (for [x (range 100000000) y (range 1000000) :while (< y x)] [x y]))"
([seq-exprs expr]
+ (assert-args for
+ (vector? seq-exprs) "a vector for its binding"
+ (even? (count seq-exprs)) "an even number of forms in binding vector")
(let [to-groups (fn [seq-exprs]
(reduce (fn [groups [k v]]
(if (keyword? k)
@@ -2812,29 +2839,29 @@
([bindings then]
`(if-let ~bindings ~then nil))
([bindings then else & oldform]
- (if (and (vector? bindings) (nil? oldform))
- (let [[form tst] bindings]
- `(let [temp# ~tst]
- (if temp#
- (let [~form temp#]
- ~then)
- ~else)))
- (throw (IllegalArgumentException.
- "if-let now requires a vector for its binding")))))
+ (assert-args if-let
+ (and (vector? bindings) (nil? oldform)) "a vector for its binding"
+ (even? (count bindings)) "exactly 2 forms in binding vector")
+ (let [[form tst] bindings]
+ `(let [temp# ~tst]
+ (if temp#
+ (let [~form temp#]
+ ~then)
+ ~else)))))
(defmacro when-let
"bindings => binding-form test
When test is true, evaluates body with binding-form bound to the value of test"
[bindings & body]
- (if (vector? bindings)
- (let [[form tst] bindings]
- `(let [temp# ~tst]
- (when temp#
- (let [~form temp#]
- ~...@body))))
- (throw (IllegalArgumentException.
- "when-let now requires a vector for its binding"))))
+ (assert-args when-let
+ (vector? bindings) "a vector for its binding"
+ (even? (count bindings)) "exactly 2 forms in binding vector")
+ (let [[form tst] bindings]
+ `(let [temp# ~tst]
+ (when temp#
+ (let [~form temp#]
+ ~...@body)))))
(defn replace
"Given a map of replacement pairs and a vector/collection, returns a
