1 define expr = {

2 number:n1 "+" expr:n2 -> n1 + n2;

3 };

4

5 define number = {

6 spaces digit+:digits -> digits |listToString |stringToNumber;

7 };

8

9 define token xs -> {

10 spaces <{xs}>;

11 };

12

13 define digit = {

14 c -> (charNumeric c) { .true -> c; .false -> error("expected", "charNumeric", c); };

15 };

16

17 spaces = {

18 (c -> (charWhitespace c) { .true -> c; .false -> error("expected", "charWhitespace", c) };)+

19 spaces;

20

21 $- $- ...

22

23 -> #t;

24 };

25

26

27 expr 1 + 2 + 3;