Revised(5) Report on the Algorithmic Language Scheme - External representations (formal)

### 7.1.2 External representations

<Datum> is what the read procedure (section 6.6.2) successfully parses. Note that any string that parses as an <expression> will also parse as a <datum>.

    <datum> ---> <simple datum> | <compound datum>

    <simple datum> ---> <boolean> | <number> | <character> | <string>
                      | <symbol>

    <symbol> ---> <identifier>

    <compound datum> ---> <list> | <vector>

    <list> ---> (<datum>*) | (<datum>+ . <datum>) | <abbreviation>

    <abbreviation> ---> <abbrev prefix> <datum>

    <abbrev prefix> ---> ' | ` | , | ,@

    <vector> ---> #(<datum>*)