map.go

     1  // run
     2  
     3  // Copyright 2021 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  package main
     8  
     9  import (
    10  	"fmt"
    11  	"reflect"
    12  	"strconv"
    13  )
    14  
    15  // Map calls the function f on every element of the slice s,
    16  // returning a new slice of the results.
    17  func mapper[F, T any](s []F, f func(F) T) []T {
    18  	r := make([]T, len(s))
    19  	for i, v := range s {
    20  		r[i] = f(v)
    21  	}
    22  	return r
    23  }
    24  
    25  func main() {
    26  	got := mapper([]int{1, 2, 3}, strconv.Itoa)
    27  	want := []string{"1", "2", "3"}
    28  	if !reflect.DeepEqual(got, want) {
    29  		panic(fmt.Sprintf("got %s, want %s", got, want))
    30  	}
    31  
    32  	fgot := mapper([]float64{2.5, 2.3, 3.5}, func(f float64) string {
    33  		return strconv.FormatFloat(f, 'f', -1, 64)
    34  	})
    35  	fwant := []string{"2.5", "2.3", "3.5"}
    36  	if !reflect.DeepEqual(fgot, fwant) {
    37  		panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
    38  	}
    39  }
    40
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