mal/plpgsql/step0_repl.sql

-- ---------------------------------------------------------
-- step0_repl.sql

\i init.sql
\i io.sql

-- ---------------------------------------------------------

CREATE SCHEMA mal;

-- read
CREATE FUNCTION mal.READ(line varchar) RETURNS varchar AS $$
BEGIN
    RETURN line;
END; $$ LANGUAGE plpgsql;

-- eval
CREATE FUNCTION mal.EVAL(ast varchar, env varchar) RETURNS varchar AS $$
BEGIN
    RETURN ast;
END; $$ LANGUAGE plpgsql;

-- print
CREATE FUNCTION mal.PRINT(exp varchar) RETURNS varchar AS $$
BEGIN
    RETURN exp;
END; $$ LANGUAGE plpgsql;


-- repl

CREATE FUNCTION mal.REP(line varchar) RETURNS varchar AS $$
BEGIN
    RETURN mal.PRINT(mal.EVAL(mal.READ(line), ''));
END; $$ LANGUAGE plpgsql;

CREATE FUNCTION mal.MAIN(pwd varchar) RETURNS integer AS $$
DECLARE
    line      varchar;
    output    varchar;
BEGIN
    WHILE true
    LOOP
        BEGIN
            line := io.readline('user> ', 0);
            IF line IS NULL THEN
                PERFORM io.close(1);
                RETURN 0;
            END IF;
            IF line NOT IN ('', E'\n') THEN
                output := mal.REP(line);
                PERFORM io.writeline(output);
            END IF;

            EXCEPTION WHEN OTHERS THEN
                PERFORM io.writeline('Error: ' || SQLERRM);
        END;
    END LOOP;
END; $$ LANGUAGE plpgsql;