;; Previously in core.rs
; Logic
(def! not (fn* [x]
    (if x nil true)))

(def! and (fn* [a b]
    (if a
        b)))

(def! or (fn* [a b]
    (if a
        a
        b)))

(def! xor (fn* [a b]
    (if a
        (not b)
        b)))

; Arithmetic
(def! abs (fn* [a]
    (if (> a 0)
        a
        (- 0 a))))

(def! mod (fn* [a b]
    (- a (* (/ a b) b))))

(def! > (fn* [a b]
    (< b a)))

(def! >= (fn* [a b]
    (not (< a b))))

(def! <= (fn* [a b]
    (>= b a)))

; Other functions in core.rs
(def! list? (fn* [a]
    (= (type a) :list)))

(def! atom? (fn* [a]
    (= (type a) :atom)))

(def! empty? (fn* [l]
    (= (count l) 0)))

(def! assert-eq (fn* [a b]
    (assert (= a b))))

(def! assert-fail (fn* [x]
    (assert (not (ok? (eval x))))))

;; File-interaction functions
(def! load-file (fn* [f]
    (eval (read-string (str "(do " (slurp f) "\nnil)")))))

(def! conf-reload (fn* []
    (load-file (str MAL_HOME "/" "config.mal"))))

;; Shorthand
(def! quit (fn* []
    (exit 0)))

;; variables
(def! MAL_HISTORY (str MAL_HOME "/" ".mal-history"))

;; helper functions
;   these functions are never called, their symbols should always resolve
;   in a special form, they are here only to provide informations through
;   the "find" and "help" functions
(def! def! (fn* [symbol value] "==SPECIAL FORM=="
    "<symbol>: Sym"
    "assign <value> to <symbol> in the current environment"
    "#returns: <value>"))

(def! let* (fn* [binding statement...] "==SPECIAL FORM=="
    "<bindings>: Vec"
    "create a new environment and assign values to symbols according"
    "to the <binding> vector then evaluate each <statement>"
    "#returns: result of the last evaluation"))

(def! do (fn* [statement...] "==SPECIAL FORM=="
    "evaluate each <statement> in the current environment"
    "#returns: result of the last evalutaion"))

(def! if (fn* [condition if-true if-false] "==SPECIAL FORM=="
    "first evaluate <condition>, based on the result of evaluation"
    "evaluates one of the two conditional branches, a missing branch"
    "evaluates to NIL"
    "#returns: result of the last evaluation"))

(def! fn* (fn* [arguments statement...] "==SPECIAL FORM=="
    "arguments: Vec"
    "#alias: λ"                                             ; >:3
    "#returns: new lambda that accepts <arguments>, evaluates each"
    "        : <statement> and returns the last evaluation's result"))

(def! help (fn* [symbol] "==SPECIAL FORM=="
    "symbol: Sym"
    "display an helper f or the specified symbol"
    "#alias: h"
    "#returns: NIL"))

(def! find (fn* [substring...] "==SPECIAL FORM=="
    "print all the known symbols partially matching <substring> in"
    "the current environment"
    "#alias f"
    "#returns: NIL"))

(def! quote (fn* [statement] "==SPECIAL FORM=="
    "prevents <statement> from being evaluated, it's possible to use"
    "the ' symbol: 'sym is equivalent to (quote sym)"))

(def! ok? (fn* [statement] "==SPECIAL FORM=="
    "evaluate <statement>"
    "#returns: true if  evaluation succeeds, NIL otherwise"))

(def! eval (fn* [statement] "==SPECIAL FORM=="
    "evaluate <statement>"
    "#returns: the result of the evaluation"))

(def! BANNER
    (str 
        "; rust-mal: a toy lisp interpreter written in rust\n"
        "; (find [pattern...])  : list symbols matching all patterns\n"
        "; (help <symbol>)      : print information about a symbol\n"
        ";\n"
        "; enjoy ^.^\n"))

(println BANNER)