ps/step1_read_print.ps

   1 (types.ps) run
   2 (reader.ps) run
   3
   4 % read
   5 /READ {
   6     /str exch def
   7     str read_str
   8 } def
   9
  10
  11 % eval
  12 /EVAL {
  13     % just "return" the "ast"
  14     /env exch def
  15     /ast exch def
  16     ast
  17 } def
  18
  19
  20 % print
  21 /PRINT {
  22     /exp exch def
  23     %(printing: ) print exp ==
  24     exp pr_str
  25 } def
  26
  27
  28 % repl
  29 /REP {
  30     READ (stub env) EVAL PRINT
  31 } def
  32
  33 /stdin (%stdin) (r) file def
  34
  35 { % loop
  36     (user> ) print flush
  37
  38     %(%lineedit) (r) file 99 string readline
  39     stdin 99 string readline
  40
  41     not { exit } if  % exit if EOF
  42
  43     %(\ngot line: ) print dup print (\n) print flush
  44     REP print (\n) print
  45 } bind loop
  46
  47 (\n) print  % final newline before exit for cleanliness
  48 quit