23 lines
552 B
TypeScript
23 lines
552 B
TypeScript
|
function map<T, U>(items: T[], f: (x: T) => U): U[]{
|
||
|
return items.map(f);
|
||
|
}
|
||
|
|
||
|
function identity<T>(x: T) {
|
||
|
return x;
|
||
|
}
|
||
|
|
||
|
function singleton<T>(x: T) {
|
||
|
return [x];
|
||
|
}
|
||
|
|
||
|
var xs = [1, 2, 3];
|
||
|
|
||
|
// Have compiler check that we get the correct types
|
||
|
var v1: number[];
|
||
|
var v1 = xs.map(identity); // Error if not number[]
|
||
|
var v1 = map(xs, identity); // Error if not number[]
|
||
|
|
||
|
var v2: number[][];
|
||
|
var v2 = xs.map(singleton); // Error if not number[][]
|
||
|
var v2 = map(xs, singleton); // Error if not number[][]
|