Predicates

plusp(v) {a bool :: (a in number)}
  Returns t if v is strictly greater than 0.

minusp(v) {a bool :: (a in number)}
  Returns t if v is strictly less than 0.

zerop(v) {a bool :: (a in number)}
  Returns t if v is equal to 0.

oddp(v) {int bool}
  Returns t if v is odd (not divisible by two).

evenp(v) {int bool}
  Returns t if v is even (divisible by two).