festival/scheme newbie question....

[Anand]

hi all,

i'm a newbie to the scheme environment and am learning it in order to
use festival. i'm trying to detect if a passed in argument to a function
is a string or not. i looked at the reference and tried to use the
function "string?" but get the following error:

festival> (string? "blah")
SIOD ERROR: unbound variable : string?

any clues what i could be doing wrong?

(and maybe a broader question, does festival even support the full list
of functions supported by scheme?)

-anand