Hi people!
I'm working on reimplement core.clj using my own C# interpreter for a
clojure-like language. Browsing in the 1.0.0 source code of core.clj, I have
some questions:
1: this is defn definition:
(def
#^{:doc "Same as (def name (fn [params* ] exprs*)) or (def
name (fn ([params* ] exprs*)+)) with any doc-string or attrs added
to the var metadata"
:arglists '([name doc-string? attr-map? [params*] body]
[name doc-string? attr-map? ([params*] body)+ attr-map?])}
defn (fn defn [name & fdecl]
(let [m (if (string? (first fdecl))
{:doc (first fdecl)}
{})
fdecl (if (string? (first fdecl))
(next fdecl)
fdecl)
m (if (map? (first fdecl))
(conj m (first fdecl))
m)
fdecl (if (map? (first fdecl))
(next fdecl)
fdecl)
fdecl (if (vector? (first fdecl))
(list fdecl)
fdecl)
m (if (map? (last fdecl))
(conj m (last fdecl))
m)
fdecl (if (map? (last fdecl))
(butlast fdecl)
fdecl)
m (conj {:arglists (list 'quote (sigs fdecl))} m)]
(list 'def (with-meta name (conj (if (meta name) (meta name) {})
m))
(cons `fn fdecl)))))
(. (var defn) (setMacro))
Why the "posponed" setMacro? Why not add the :macro true to inital metadata,
directly?
2) The cond macro is defined:
(defmacro cond
"Takes a set of test/expr pairs. It evaluates each test one at a
time. If a test returns logical true, cond evaluates and returns
the value of the corresponding expr and doesn't evaluate any of the
other tests or exprs. (cond) returns nil."
[& clauses]
(when clauses
(list 'if (first clauses)
(if (next clauses)
(second clauses)
(throw (IllegalArgumentException.
"cond requires an even number of forms")))
(cons 'clojure.core/cond (next (next clauses))))))
Why the need of add the full namespace name in the last cons?
Ok, but the first use of it is in:
(defn spread
{:private true}
[arglist]
(cond
(nil? arglist) nil
(nil? (next arglist)) (seq (first arglist))
:else (cons (first arglist) (spread (next arglist)))))
Where is defined :else keyword behaviour? I can't find how :else is defined
to be managed in cond/if code
TIA
Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez
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