Usage: not x
True iff x is absent or false
True iff x is absent
True iff x is absent
True iff both b0 and b1 are absent or both are present and have the same value.
True iff b0 occurs and is equal to b1
True iff b1 occurs and is equal to b0
Return value of x (assumes that x is not absent)
Return value of x (assumes that x is not absent)
Return absent if idx is absent, otherwise return x[idx]
Return absent if idx1 or idx2 is absent, otherwise return x[idx1, idx2]
Return x[idx]
Return x[idx1, idx2]
Return absent if idx is absent, otherwise return x[idx]
Return absent if idx1 or idx2 is absent, otherwise return x[idx1, idx2]
True iff for at least one i, x[i] occurs and is true
True iff for any i, x[i] is absent or true
True iff x is not absent