Chez Phase 3 inc 5c: reader dispatch (#) in jolt.reader
Ports the full # dispatch to the portable reader: #{} sets, #() anon-fns, #?/#?@
reader-conditionals, #_ discard, #' var-quote, #"" regex, #inst/#uuid/#tag tagged
literals, ## symbolic (Inf/-Inf/NaN), and #^ deprecated metadata. With this the
reader is feature-complete except position tracking + wire-in (inc 5d).
Reader-conditionals resolve clause-order against a portable feature set (atom
#{:jolt :default}); #? -> :skip / :form, #?@ -> :splice (the control protocol from
5b). #() uses the two-pass %-scan (collect indices, then rebuild replacing %N/%/%&
with gensym params) over the form tree via the jolt.host form-* contract. Three
host constructors added: form-make-set, form-make-tagged, form-gensym-name.
reader-parity 149/149. #() compares modulo gensym (canonicalize #-suffixed param
names by first-occurrence order — the two readers gensym different names but the
structure + %-mapping must match). ##NaN checked by the NaN!=NaN property. Full jpm
gate green (prelude pre-warmed). jolt-9ufe.
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3 changed files with 210 additions and 3 deletions
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@ -20,8 +20,12 @@
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(:require [clojure.string :as str]
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[jolt.host :refer [form-make-symbol form-make-char form-char-from-name
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form-scan-number form-make-list form-make-vector
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form-make-map form-sym-merge-meta
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form-sym? form-sym-name form-sym-ns form-char?]]))
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form-make-map form-sym-merge-meta form-make-set
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form-make-tagged form-gensym-name
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form-sym? form-sym-name form-sym-ns form-char?
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form-list? form-vec? form-set? form-map?
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form-elements form-vec-items form-set-items
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form-map-pairs]]))
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;; Source access by CHARACTER codepoint, mirroring the Janet reader's byte access
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;; (identical for ASCII). cp = codepoint at i; len = character count.
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@ -274,6 +278,151 @@
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;; raw map-literal meta when m is nil)
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[:form (form-make-list [(form-make-symbol "with-meta") form (if m m meta-form)]) np2])))
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;; --- dispatch (#) ------------------------------------------------------------
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;; Reader-conditional feature set (spec 02-reader). jolt's portable default; the
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;; JOLT_FEATURES env override is a host concern wired later. :default always honored.
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(def reader-features (atom #{:jolt :default}))
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(defn set-reader-features! [features] (reset! reader-features (conj (set features) :default)))
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(defn- read-set* [s pos]
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;; pos at #, next char {
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(let [[items end] (read-delimited s (+ pos 2) 125 "Unterminated set")] ; }
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[:form (form-make-set items) end]))
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(defn- read-var-quote* [s pos]
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;; pos at #, next char '
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(let [[form np] (read-next-form s (+ pos 2))]
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[:form (form-make-list [(form-make-symbol "var") form]) np]))
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(defn- read-regex* [s pos]
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;; pos at #, next char "; read raw to the unescaped closing " (backslashes kept)
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(loop [i (+ pos 2)]
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(when (>= i (len s)) (throw (ex-info "Unterminated regex literal" {})))
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(let [c (cp s i)]
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(cond
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(= c 92) (recur (+ i 2)) ; backslash escapes next char
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(= c 34) [:form (form-make-tagged :regex (subs s (+ pos 2) i)) (inc i)]
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:else (recur (inc i))))))
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;; #?(…) / #?@(…): pick the first clause whose feature key is active (clause order,
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;; like Clojure). #? -> :skip when the result is nil (e.g. a :cljs branch); #?@ ->
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;; :splice the resolved items into the enclosing collection.
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(defn- rc-resolve [clauses]
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;; clauses: a jolt vector of [feature-kw form feature-kw form ...]
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(loop [i 0]
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(if (>= i (count clauses))
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[false nil]
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(if (contains? @reader-features (nth clauses i))
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[true (nth clauses (inc i))]
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(recur (+ i 2))))))
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(defn- read-reader-conditional* [s pos]
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;; pos at #, next char ? (optionally ?@)
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(let [splice? (and (< (+ pos 2) (len s)) (= (cp s (+ pos 2)) 64)) ; @
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form-start (if splice? (+ pos 3) (+ pos 2))
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[form np] (read-next-form s form-start)]
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(if (form-list? form)
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(let [clauses (form-elements form)
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[matched result] (rc-resolve clauses)]
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(if splice?
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(let [items (cond (not matched) []
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(form-list? result) (vec (form-elements result))
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(form-vec? result) (vec (form-vec-items result))
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:else [result])]
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[:splice items np])
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(if (or (not matched) (nil? result)) [:skip nil np] [:form result np])))
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(throw (ex-info "reader conditional body must be a list" {})))))
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;; Symbolic values ##Inf ##-Inf ##NaN.
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(defn- read-symbolic* [s pos]
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(let [end (read-symbol-name s (+ pos 2) (+ pos 2))
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nm (subs s (+ pos 2) end)]
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(cond
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(= nm "Inf") [:form ##Inf end]
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(= nm "-Inf") [:form ##-Inf end]
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(= nm "NaN") [:form ##NaN end]
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:else (throw (ex-info (str "Invalid symbolic value: ##" nm) {})))))
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(defn- read-tagged* [s pos]
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;; unknown dispatch -> a tagged literal (#inst, #uuid, #foo). The tag includes
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;; the leading # (read-symbol-name starts at #), matching the Janet reader.
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(let [end (read-symbol-name s pos pos)
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tag (subs s pos end)
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[form np] (read-next-form s end)]
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[:form (form-make-tagged (keyword tag) form) np]))
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(declare read-anon-fn*)
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(defn- read-dispatch* [s pos]
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;; pos at #
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(when (>= (inc pos) (len s)) (throw (ex-info "Unexpected end after #" {})))
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(let [c (cp s (inc pos))]
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(cond
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(= c 123) (read-set* s pos) ; #{
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(= c 40) (read-anon-fn* s pos) ; #(
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(= c 63) (read-reader-conditional* s pos) ; #?
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(= c 95) (let [[_ _ np] (read-form s (+ pos 2))] [:skip nil np]) ; #_ discard
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(= c 39) (read-var-quote* s pos) ; #'
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(= c 94) (read-meta* s (inc pos)) ; #^ (deprecated, = ^)
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(= c 34) (read-regex* s pos) ; #"
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(= c 35) (read-symbolic* s pos) ; ##
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:else (read-tagged* s pos))))
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;; #(...) anonymous fn. Positional %-arg index: % and %1 => 1, %N => N, %& => the
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;; rest param (:rest); anything else is not positional (nil). Fixed arity = max
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;; index used (Clojure: #(do %2 %&) => [p1 p2 & rest], unused lower slots still
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;; get a placeholder param).
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(defn- pct-index [nm]
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(cond
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(= nm "%") 1
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(= nm "%&") :rest
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(and (> (count nm) 1) (= "%" (subs nm 0 1)))
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(let [n (form-scan-number (subs nm 1))]
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(if (and n (integer? n) (>= n 1)) n nil))
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:else nil))
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;; Pass 1: collect every %-index used anywhere in the form tree.
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(defn- collect-pcts [form acc]
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(cond
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(form-sym? form) (let [i (pct-index (form-sym-name form))] (if i (conj acc i) acc))
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(form-list? form) (reduce (fn [a x] (collect-pcts x a)) acc (form-elements form))
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(form-vec? form) (reduce (fn [a x] (collect-pcts x a)) acc (form-vec-items form))
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(form-set? form) (reduce (fn [a x] (collect-pcts x a)) acc (form-set-items form))
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(form-map? form) (reduce (fn [a p] (collect-pcts (nth p 1) (collect-pcts (nth p 0) a)))
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acc (form-map-pairs form))
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:else acc))
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;; Pass 2: replace each %-symbol with its slot's gensym (rebuilding collections).
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(defn- replace-pct [form slot-syms rest-sym]
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(cond
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(form-sym? form) (let [idx (pct-index (form-sym-name form))]
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(cond (= idx :rest) rest-sym
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idx (get slot-syms idx)
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:else form))
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(form-list? form) (form-make-list (mapv #(replace-pct % slot-syms rest-sym) (form-elements form)))
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(form-vec? form) (form-make-vector (mapv #(replace-pct % slot-syms rest-sym) (form-vec-items form)))
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(form-set? form) (form-make-set (mapv #(replace-pct % slot-syms rest-sym) (form-set-items form)))
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(form-map? form) (form-make-map
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(vec (mapcat (fn [p] [(replace-pct (nth p 0) slot-syms rest-sym)
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(replace-pct (nth p 1) slot-syms rest-sym)])
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(form-map-pairs form))))
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:else form))
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(defn- gensym-param [] (form-make-symbol (str (form-gensym-name) "#")))
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(defn- read-anon-fn* [s pos]
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;; pos at #, next char (
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(let [[form np] (read-next-form s (inc pos))
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pcts (collect-pcts form [])
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max-n (reduce (fn [m i] (if (and (number? i) (> i m)) i m)) 0 pcts)
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has-rest (boolean (some #(= :rest %) pcts))
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slot-syms (into {} (map (fn [i] [i (gensym-param)]) (range 1 (inc max-n))))
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rest-sym (when has-rest (gensym-param))
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replaced (replace-pct form slot-syms rest-sym)
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arg-names (let [base (mapv #(get slot-syms %) (range 1 (inc max-n)))]
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(if has-rest (conj base (form-make-symbol "&") rest-sym) base))]
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[:form (form-make-list [(form-make-symbol "fn*") (form-make-vector arg-names) replaced]) np]))
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(defn read-form [s pos]
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(let [pos (skip-whitespace s pos)]
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(if (>= pos (len s))
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@ -297,7 +446,7 @@
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(= c 41) (throw (ex-info "Unmatched delimiter: )" {}))
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(= c 93) (throw (ex-info "Unmatched delimiter: ]" {}))
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(= c 125) (throw (ex-info "Unmatched delimiter: }" {}))
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(= c 35) (throw (ex-info "read-form: dispatch (#) not yet ported (inc 5c)" {})) ; #
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(= c 35) (read-dispatch* s pos) ; #
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(number-start? s pos c) (let [r (read-number* s pos)] [:form (nth r 0) (nth r 1)])
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(symbol-start? c) (let [r (read-symbol* s pos)] [:form (nth r 0) (nth r 1)])
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:else (throw (ex-info (str "read-form: unexpected char '" (char c) "' (" c ")") {})))))))
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