You can test that a value matches a regular expression by using a regular expression literal:
+@ (/username:\s*[a-zA-Z]*$/) -> Bool
+function checkUsername(str) {
+ // ...
+ return true;
+}
+
+checkUsername("username: bob"); // passes
+checkUsername("user: bob"); // failsAll of the basic contracts are built with predicates (functions that take a single value and return a boolean) and you can make your own:
function MyNum(val) {
return typeof val === "number";