A hand of poker is divided into betting rounds. During a given betting
round, each remaining player in turn takes one of the actions below.
Betting proceeds in a circle until each player has either called all bets
or folded.
check, a bet of zero that does not forfeit interest in the pot
bet or raise, a nonzero bet greater than preceding bets
that all successive players must match or exceed or else forfeit all
interest in the pot
call, a nonzero bet equal to a preceding bet that maintains a
player's interest in the pot
fold, a surrender of interest in the pot in response to another
player's bet, accompanied by the loss of one's cards and previous bets