UNGETCHAR returns the character. So one can write (ungetchar ps (getchar ps)) to peek idempotently.

Author Pascal J. Bourguignon <pjb@informatimago.com>
Author date 2012-02-16 08:04:53
Author local date 2012-02-16 09:04:53 +0100
Committer Pascal J. Bourguignon <pjb@informatimago.com>
Committer date 2012-02-16 08:04:53
Committer local date 2012-02-16 09:04:53 +0100
Commit f6f06251a1f96f7fbd8114f65f208c5db673a8aa
Tree 7334da0ab1bce1503dfdd9f828b6b004977151e6
Parent dd43920df020cbaffc84ea6eba04d35b373795bd
UNGETCHAR returns the character.  So one can write (ungetchar ps (getchar ps)) to peek idempotently.
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