diff options
Diffstat (limited to 'doc/articles/slices_usage_and_internals.html')
| -rw-r--r-- | doc/articles/slices_usage_and_internals.html | 53 |
1 files changed, 6 insertions, 47 deletions
diff --git a/doc/articles/slices_usage_and_internals.html b/doc/articles/slices_usage_and_internals.html index c10dfe0ca..810b0a41f 100644 --- a/doc/articles/slices_usage_and_internals.html +++ b/doc/articles/slices_usage_and_internals.html @@ -1,11 +1,7 @@ <!--{ - "Title": "Slices: usage and internals" + "Title": "Slices: usage and internals", + "Template": true }--> -<!-- - DO NOT EDIT: created by - tmpltohtml articles/slices_usage_and_internals.tmpl ---> - <p> Go's slice type provides a convenient and efficient means of working with @@ -326,20 +322,7 @@ appends byte elements to a slice of bytes, growing the slice if necessary, and returns the updated slice value: </p> -<pre><!--{{code "progs/slices.go" `/AppendByte/` `/STOP/`}} --->func AppendByte(slice []byte, data ...byte) []byte { - m := len(slice) - n := m + len(data) - if n > cap(slice) { // if necessary, reallocate - // allocate double what's needed, for future growth. - newSlice := make([]byte, (n+1)*2) - copy(newSlice, slice) - slice = newSlice - } - slice = slice[0:n] - copy(slice[m:n], data) - return slice -}</pre> +{{code "/doc/progs/slices.go" `/AppendByte/` `/STOP/`}} <p> One could use <code>AppendByte</code> like this: @@ -398,18 +381,7 @@ Since the zero value of a slice (<code>nil</code>) acts like a zero-length slice, you can declare a slice variable and then append to it in a loop: </p> -<pre><!--{{code "progs/slices.go" `/Filter/` `/STOP/`}} --->// Filter returns a new slice holding only -// the elements of s that satisfy f() -func Filter(s []int, fn func(int) bool) []int { - var p []int // == nil - for _, i := range s { - if fn(i) { - p = append(p, i) - } - } - return p -}</pre> +{{code "/doc/progs/slices.go" `/Filter/` `/STOP/`}} <p> <b>A possible "gotcha"</b> @@ -428,13 +400,7 @@ searches it for the first group of consecutive numeric digits, returning them as a new slice. </p> -<pre><!--{{code "progs/slices.go" `/digit/` `/STOP/`}} --->var digitRegexp = regexp.MustCompile("[0-9]+") - -func FindDigits(filename string) []byte { - b, _ := ioutil.ReadFile(filename) - return digitRegexp.Find(b) -}</pre> +{{code "/doc/progs/slices.go" `/digit/` `/STOP/`}} <p> This code behaves as advertised, but the returned <code>[]byte</code> points @@ -449,14 +415,7 @@ To fix this problem one can copy the interesting data to a new slice before returning it: </p> -<pre><!--{{code "progs/slices.go" `/CopyDigits/` `/STOP/`}} --->func CopyDigits(filename string) []byte { - b, _ := ioutil.ReadFile(filename) - b = digitRegexp.Find(b) - c := make([]byte, len(b)) - copy(c, b) - return c -}</pre> +{{code "/doc/progs/slices.go" `/CopyDigits/` `/STOP/`}} <p> A more concise version of this function could be constructed by using |