7 Contracts
| (require (planet cce/scheme:6:2/contract)) |
This module provides useful contracts and contract constructors.
7.1 Flat Contracts
This contract recognizes natural numbers that satisfy
exact-nonnegative-integer?.
This contract recognizes positive integers that satisfy
exact-positive-integer?.
This contract recognizes Scheme truth values, i.e., any value, but with a more
informative name and description. Use it in negative positions for arguments
that accept arbitrary truth values that may not be booleans.
7.2 Higher-Order Contracts
These contracts recognize functions that accept 0, 1, or 2 arguments,
respectively, and produce a single result.
These contracts recognize predicates: functions of a single argument that
produce a boolean result.
The first constrains its output to satisfy boolean?. Use predicate/c in positive position for predicates that guarantee a result of #t or #f.
The second constrains its output to satisfy truth/c. Use predicate-like/c in negative position for predicates passed as arguments that may return arbitrary values as truth values.
These contracts recognize comparisons: functions of two arguments that
produce a boolean result.
The first constrains its output to satisfy boolean?. Use comparison/c in positive position for comparisons that guarantee a result of #t or #f.
The second constrains its output to satisfy truth/c. Use comparison-like/c in negative position for comparisons passed as arguments that may return arbitrary values as truth values.