ps/step8_macros.ps

   1 /runlibfile where { pop }{ /runlibfile { run } def } ifelse %
   2 (types.ps) runlibfile
   3 (reader.ps) runlibfile
   4 (printer.ps) runlibfile
   5 (env.ps) runlibfile
   6 (core.ps) runlibfile
   7
   8 % read
   9 /_readline { print flush (%stdin) (r) file 1024 string readline } def
  10
  11 /READ {
  12     /str exch def
  13     str read_str
  14 } def
  15
  16
  17 % eval
  18 % is_pair?: ast -> is_pair? -> bool
  19 % return true if non-empty list, otherwise false
  20 /is_pair? {
  21     dup _sequential? { _count 0 gt }{ pop false } ifelse
  22 } def
  23
  24 % ast -> quasiquote -> new_ast
  25 /quasiquote { 3 dict begin
  26     /ast exch def
  27     ast is_pair? not { %if not is_pair?
  28         /quote ast 2 _list
  29     }{
  30         /a0 ast 0 _nth def
  31         a0 /unquote eq { %if a0 unquote symbol
  32             ast 1 _nth
  33         }{ a0 is_pair? { %elseif a0 is_pair?
  34             /a00 a0 0 _nth def
  35             a00 /splice-unquote eq { %if splice-unquote
  36                 /concat a0 1 _nth ast _rest quasiquote 3 _list
  37             }{ %else not splice-unquote
  38                 /cons a0 quasiquote ast _rest quasiquote 3 _list
  39             } ifelse
  40         }{ % else not a0 is_pair?
  41             /cons a0 quasiquote ast _rest quasiquote 3 _list
  42         } ifelse } ifelse
  43     } ifelse
  44 end } def
  45
  46 /is_macro_call? { 3 dict begin
  47     /env exch def
  48     /ast exch def
  49     ast _list? {
  50         /a0 ast 0 _nth def
  51         a0 _symbol? { %if a0 is symbol
  52             env a0 env_find null ne { %if a0 is in env
  53                 env a0 env_get _mal_function? { %if user defined function
  54                     env a0 env_get /macro? get true eq %if marked as macro
  55                 }{ false } ifelse
  56             }{ false } ifelse
  57         }{ false } ifelse
  58     }{ false } ifelse
  59 end } def
  60
  61 /macroexpand { 3 dict begin
  62     /env exch def
  63     /ast exch def
  64     {
  65         ast env is_macro_call? {
  66             /mac env   ast 0 _nth   env_get def
  67             /ast ast _rest mac fload EVAL def
  68         }{
  69             exit
  70         } ifelse
  71     } loop
  72     ast
  73 end } def
  74
  75 /eval_ast { 2 dict begin
  76     /env exch def
  77     /ast exch def
  78     %(eval_ast: ) print ast ==
  79     ast _symbol? { %if symbol
  80         env ast env_get
  81     }{ ast _sequential? { %elseif list or vector
  82         [
  83             ast /data get { %forall items
  84                 env EVAL
  85             } forall
  86         ] ast _list? { _list_from_array }{ _vector_from_array } ifelse
  87     }{ ast _hash_map? { %elseif list or vector
  88         <<
  89             ast /data get { %forall entries
  90                 env EVAL
  91             } forall
  92         >> _hash_map_from_dict
  93     }{ % else
  94         ast
  95     } ifelse } ifelse } ifelse
  96 end } def
  97
  98 /EVAL { 13 dict begin
  99     { %loop (TCO)
 100
 101     /env exch def
 102     /ast exch def
 103     /loop? false def
 104
 105     %(EVAL: ) print ast true _pr_str print (\n) print
 106     ast _list? not { %if not a list
 107         ast env eval_ast
 108     }{ %else apply the list
 109       /ast ast env macroexpand def
 110       ast _list? not { %if no longer a list
 111           ast env eval_ast
 112       }{ %else still a list
 113         /a0 ast 0 _nth def
 114         /def! a0 eq { %if def!
 115             /a1 ast 1 _nth def
 116             /a2 ast 2 _nth def
 117             env a1  a2 env EVAL  env_set
 118         }{ /let* a0 eq { %if let*
 119             /a1 ast 1 _nth def
 120             /a2 ast 2 _nth def
 121             /let_env env null null env_new def
 122             0 2 a1 _count 1 sub { %for each pair
 123                 /idx exch def
 124                 let_env
 125                     a1 idx _nth
 126                     a1 idx 1 add _nth let_env EVAL
 127                     env_set
 128                     pop % discard the return value
 129             } for
 130             a2
 131             let_env
 132             /loop? true def % loop
 133         }{ /quote a0 eq { %if quote
 134             ast 1 _nth
 135         }{ /quasiquote a0 eq { %if quasiquote
 136             ast 1 _nth quasiquote
 137             env
 138             /loop? true def % loop
 139         }{ /defmacro! a0 eq { %if defmacro!
 140             /a1 ast 1 _nth def
 141             /a2 ast 2 _nth def
 142             a2 env EVAL
 143             dup /macro? true put % set macro flag
 144             env exch a1 exch env_set % def! it
 145         }{ /macroexpand a0 eq { %if defmacro!
 146             ast 1 _nth env macroexpand
 147         }{ /do a0 eq { %if do
 148             ast _count 2 gt { %if ast has more than 2 elements
 149                 ast 1 ast _count 2 sub _slice env eval_ast pop
 150             } if
 151             ast ast _count 1 sub _nth % last ast becomes new ast
 152             env
 153             /loop? true def % loop
 154         }{ /if a0 eq { %if if
 155             /a1 ast 1 _nth def
 156             /cond a1 env EVAL def
 157             cond null eq cond false eq or { % if cond is nil or false
 158                 ast _count 3 gt { %if false branch with a3
 159                     ast 3 _nth env
 160                     /loop? true def
 161                 }{ % else false branch with no a3
 162                     null
 163                 } ifelse
 164             }{ % true branch
 165                 ast 2 _nth env
 166                 /loop? true def
 167             } ifelse
 168         }{ /fn* a0 eq { %if fn*
 169             /a1 ast 1 _nth def
 170             /a2 ast 2 _nth def
 171             a2 env a1 _mal_function
 172         }{
 173             /el ast env eval_ast def
 174             el _rest el _first % stack: ast function
 175             dup _mal_function? { %if user defined function
 176                 fload % stack: ast new_env
 177                 /loop? true def
 178             }{ dup _function? { %else if builtin function
 179                 /data get exec
 180             }{ %else (regular procedure/function)
 181                 (cannot apply native proc!\n) print quit
 182             } ifelse } ifelse
 183         } ifelse } ifelse } ifelse } ifelse } ifelse } ifelse } ifelse } ifelse } ifelse
 184       } ifelse
 185     } ifelse
 186
 187     loop? not { exit } if
 188     } loop % TCO
 189 end } def
 190
 191
 192 % print
 193 /PRINT {
 194     true _pr_str
 195 } def
 196
 197
 198 % repl
 199 /repl_env null null null env_new def
 200
 201 /RE { READ repl_env EVAL } def
 202 /REP { READ repl_env EVAL PRINT } def
 203
 204 % core.ps: defined using postscript
 205 /_ref { repl_env 3 1 roll env_set pop } def
 206 core_ns { _function _ref } forall
 207 (eval) { 0 _nth repl_env EVAL } _function _ref
 208 (*ARGV*) [ ] _list_from_array _ref
 209
 210 % core.mal: defined using the language itself
 211 (\(def! not \(fn* \(a\) \(if a false true\)\)\)) RE pop
 212 (\(def! load-file \(fn* \(f\) \(eval \(read-string \(str "\(do " \(slurp f\) "\)"\)\)\)\)\)) RE pop
 213 (\(defmacro! cond \(fn* \(& xs\) \(if \(> \(count xs\) 0\) \(list 'if \(first xs\) \(if \(> \(count xs\) 1\) \(nth xs 1\) \(throw "odd number of forms to cond"\)\) \(cons 'cond \(rest \(rest xs\)\)\)\)\)\)\)) RE pop
 214 (\(defmacro! or \(fn* \(& xs\) \(if \(empty? xs\) nil \(if \(= 1 \(count xs\)\) \(first xs\) `\(let* \(or_FIXME ~\(first xs\)\) \(if or_FIXME or_FIXME \(or ~@\(rest xs\)\)\)\)\)\)\)\)) RE pop
 215
 216 userdict /ARGUMENTS known { %if command line arguments
 217     ARGUMENTS length 0 gt { %if more than 0 arguments
 218         (*ARGV*) ARGUMENTS 1 ARGUMENTS length 1 sub getinterval
 219         _list_from_array _ref
 220         ARGUMENTS 0 get
 221         (\(load-file ") exch ("\)) concatenate concatenate RE pop
 222         quit
 223     } if
 224 } if
 225
 226 % repl loop
 227 { %loop
 228     (user> ) _readline
 229     not { exit } if  % exit if EOF
 230
 231     { %try
 232         REP print (\n) print
 233     } stopped {
 234         (Error: ) print
 235         get_error_data false _pr_str print (\n) print
 236         $error /newerror false put
 237         $error /errorinfo null put
 238         clear
 239         cleardictstack
 240     } if
 241 } bind loop
 242
 243 (\n) print  % final newline before exit for cleanliness
 244 quit