plpgsql/step0_repl.sql

   1 -- ---------------------------------------------------------
   2 -- step0_repl.sql
   3
   4 \i init.sql
   5 \i io.sql
   6
   7 -- ---------------------------------------------------------
   8
   9 CREATE SCHEMA mal;
  10
  11 -- read
  12 CREATE FUNCTION mal.READ(line varchar) RETURNS varchar AS $$
  13 BEGIN
  14     RETURN line;
  15 END; $$ LANGUAGE plpgsql;
  16
  17 -- eval
  18 CREATE FUNCTION mal.EVAL(ast varchar, env varchar) RETURNS varchar AS $$
  19 BEGIN
  20     RETURN ast;
  21 END; $$ LANGUAGE plpgsql;
  22
  23 -- print
  24 CREATE FUNCTION mal.PRINT(exp varchar) RETURNS varchar AS $$
  25 BEGIN
  26     RETURN exp;
  27 END; $$ LANGUAGE plpgsql;
  28
  29
  30 -- repl
  31
  32 CREATE FUNCTION mal.REP(line varchar) RETURNS varchar AS $$
  33 BEGIN
  34     RETURN mal.PRINT(mal.EVAL(mal.READ(line), ''));
  35 END; $$ LANGUAGE plpgsql;
  36
  37 CREATE FUNCTION mal.MAIN(pwd varchar) RETURNS integer AS $$
  38 DECLARE
  39     line      varchar;
  40     output    varchar;
  41 BEGIN
  42     WHILE true
  43     LOOP
  44         BEGIN
  45             line := io.readline('user> ', 0);
  46             IF line IS NULL THEN
  47                 PERFORM io.close(1);
  48                 RETURN 0;
  49             END IF;
  50             IF line NOT IN ('', E'\n') THEN
  51                 output := mal.REP(line);
  52                 PERFORM io.writeline(output);
  53             END IF;
  54
  55             EXCEPTION WHEN OTHERS THEN
  56                 PERFORM io.writeline('Error: ' || SQLERRM);
  57         END;
  58     END LOOP;
  59 END; $$ LANGUAGE plpgsql;