/runlibfile where { pop }{ /runlibfile { run } def } ifelse % 
(types.ps) runlibfile
(reader.ps) runlibfile
(printer.ps) runlibfile
(env.ps) runlibfile

% read
/_readline { print flush (%stdin) (r) file 1024 string readline } def

/READ {
    /str exch def
    str read_str
} def


% eval
/EVAL { 7 dict begin
    /env exch def
    /ast exch def

    env (DEBUG-EVAL) env_get {
        dup null ne    exch false ne    and {
            (EVAL: ) print
            ast true _pr_str print
            (\n) print
        } if
    } if

    ast _symbol? { %if symbol
        env ast env_get
        not {
            (') ast
            dup length string cvs
            (' not found)
            concatenate concatenate
            _throw
        } if
    }{

    ast _vector? {
        [
            ast /data get { %forall items
                env EVAL
            } forall
        ] _vector_from_array
    }{

    ast _hash_map? {
        <<
            ast /data get { %forall entries
                env EVAL
            } forall
        >> _hash_map_from_dict
    }{

    ast _list? not {
        ast
    }{

    ast _count 0 eq {
        ast
    }{

        /a0 ast 0 _nth def

        /def! a0 eq { %if def!
            ast 2 _nth    env EVAL
            env    ast 1 _nth    2 index    env_set
        }{

        /let* a0 eq { %if let*
            /a1 ast 1 _nth def
            /a2 ast 2 _nth def
            /let_env env null null env_new def
            0 2 a1 _count 1 sub { %for each pair
                /idx exch def
                let_env
                    a1 idx _nth
                    a1 idx 1 add _nth let_env EVAL
                    env_set
            } for
            a2 let_env EVAL
        }{

            a0 env EVAL

            [ ast _rest /data get { env EVAL } forall ] _list_from_array exch
            exec % apply function to args

        } ifelse } ifelse } ifelse } ifelse } ifelse } ifelse } ifelse
end } def


% print
/PRINT {
    true _pr_str
} def


% repl
/repl_env null null null env_new def

/REP { READ repl_env EVAL PRINT } def

repl_env (+) { dup 0 _nth exch 1 _nth add } env_set
repl_env (-) { dup 0 _nth exch 1 _nth sub } env_set
repl_env (*) { dup 0 _nth exch 1 _nth mul } env_set
repl_env (/) { dup 0 _nth exch 1 _nth idiv } env_set

% repl loop
{ %loop
    (user> ) _readline
    not { exit } if  % exit if EOF

    { %try
        REP print (\n) print
    } stopped {
        (Error: ) print
        get_error_data false _pr_str print (\n) print
        $error /newerror false put
        $error /errorinfo null put
        clear
        cleardictstack
    } if
} bind loop

(\n) print  % final newline before exit for cleanliness
quit