precondition-satisfied.dfy(12,4): Error: function precondition could not be proved
 Asserted expression: b != 0
precondition-satisfied.dfy(5,15): Related location: this proposition could not be proved
precondition-satisfied.dfy(23,4): Error: divisor must be nonzero
 Asserted expression: b != 0
precondition-satisfied.dfy(16,72): Related location: this proposition could not be proved
precondition-satisfied.dfy(29,4): Error: function precondition could not be proved
 Asserted expression: lam.requires(a, b)
precondition-satisfied.dfy(34,4): Error: function precondition could not be proved
 Asserted expression: ((x: int, y: int) requires y != 0 => x / y).requires(a, b)

Dafny program verifier finished with 2 verified, 4 errors
