ps/env.ps

   1 % outer binds exprs -> env_new -> new_env
   2 /env_new { 3 dict begin
   3     %(in env_new\n) print
   4     /exprs exch dup _sequential? { /data get }{ pop [ ] } ifelse def
   5     /binds exch dup _sequential? { /data get }{ pop [ ] } ifelse def
   6     /outer exch def
   7     <<
   8         /__outer__ outer
   9         0 1 binds length 1 sub {
  10             /idx exch def
  11             binds idx get (&) eq { %if &
  12                 binds idx 1 add get % key
  13                 exprs idx   exprs length idx sub   getinterval % value
  14                 _list_from_array
  15                 exit
  16             } if
  17             binds idx get % key
  18             exprs idx get % value
  19         } for
  20     >>
  21 end } def
  22
  23 % env key -> env_find -> env
  24 % env key -> env_find -> null
  25 /env_find { 2 dict begin
  26     /key exch def
  27     /env exch def
  28     env key known { %if key in env
  29         env
  30     }{ env /__outer__ get null ne { %elseif __outer__ not null
  31         env /__outer__ get   key env_find
  32     }{ %else
  33         null
  34     } ifelse } ifelse
  35 end } def
  36
  37 % env key val -> env_set -> val
  38 /env_set {
  39     dup 4 1 roll % stack: val env key val
  40     put % stack: val
  41 } def
  42
  43 /env_get {
  44     dup 3 1 roll % stack: key env key
  45     env_find % stack: key env/null
  46     dup null eq {
  47         pop % stack: key
  48         (') exch % stack: (') key
  49         dup length string cvs
  50         (' not found)
  51         concatenate concatenate
  52         _throw
  53     }{
  54         exch % stack: env key
  55         get
  56     } ifelse
  57 } def