publish regular-expressions

examples/regular-expressions/regular-expressions.go

@@ -4,37 +4,76 @@
 
 package main
 
+import "bytes"
 import "fmt"
 import "regexp"
 
 func main() {
 
     // This tests whether a pattern matches a string.
-    match, _ := regexp.MatchString("p[a-z]+ch", "apple")
-    fmt.Println("match:", match)
+    match, _ := regexp.MatchString("p([a-z]+)ch", "peach")
+    fmt.Println(match)
 
-    // In the above example we used a string pattern
-    // directly. For other regular expression tasks you'll
-    // need to `Compile` a `Regexp` struct.
-    r1, _ := regexp.Compile("p[a-z]+ch")
+    // Above we used a string pattern directly, but for
+    // other regexp tasks you'll need to `Compile` an
+    // optimized `Regexp` struct.
+    r, _ := regexp.Compile("p([a-z]+)ch")
 
     // Many methods are available on these structs. Here's
     // a match test like we saw earlier.
-    fmt.Println("match:", r1.MatchString("apple"))
+    fmt.Println(r.MatchString("peach"))
 
-    //
+    // This finds the match for the regexp.
+    fmt.Println(r.FindString("peach punch"))
 
-    // When creating top-level constants with regular
-    // expressions, you can use the `MustCompile` variant
-    // of the `Compile` function we saw earlier. A plain
-    // `Compile` won't work for constants because it has 2
-    // return values.
-    cr := regexp.MustCompile("p[a-z]+ch")
-    fmt.Println("regex:", cr)
+    // The also finds the first match but returns the
+    // start and end indexes for the match instead of the
+    // matching text.
+    fmt.Println(r.FindStringIndex("peach punch"))
 
+    // The `Submatch` variants include information about
+    // both the whole-pattern matches and the submatches
+    // within those matches. For example this will return
+    // information for both `p([a-z]+)ch` and `([a-z]+)`.
+    fmt.Println(r.FindStringSubmatch("peach punch"))
+
+    // Similarly this will return information about the
+    // indexes of matches and submatches.
+    fmt.Println(r.FindStringSubmatchIndex("peach punch"))
+
+    // The `All` variants of these functions apply to all
+    // matches in the input, not just the first. For
+    // example to find all matches for a regexp.
+    fmt.Println(r.FindAllString("peach punch pinch", -1))
+
+    // Providing a non-negative integer as the second
+    // argument to these functions will limit the number
+    // of matches.
+    fmt.Println(r.FindAllString("peach punch pinch", 2))
+
+    // Our examples above had string arguments and used
+    // names like `MatchString`. We can also provide
+    // `[]byte` arguments and drop `String` from the
+    // function name.
+    fmt.Println(r.Match([]byte("peach")))
+
+    // When creating constants with regular expressions
+    // you can use the `MustCompile` variation of
+    // `Compile`. A plain `Compile` won't work for
+    // constants because it has 2 return values.
+    r = regexp.MustCompile("p([a-z]+)ch")
+    fmt.Println(r)
+
+    // The `regexp` package can also be used to replace
+    // subsets of strings with other values.
+    fmt.Println(r.ReplaceAllString("a peach", "<fruit>"))
+
+    // The `Func` variant allows you to transform matched
+    // text with a given function.
+    in := []byte("a peach")
+    out := r.ReplaceAllFunc(in, bytes.ToUpper)
+    fmt.Println(string(out))
 }
 
-// todo: 
-// todo: gsub
-
+// todo: Find(All)?(String)?(Submatch)?(Index)?
 // todo: Examples of regular expressions in #golang: https://gobyexample.com/regular-expressions One of the best areas for a "by example" approach IMO.

examples/regular-expressions/regular-expressions.sh

@@ -1,4 +1,16 @@
 $ go run regular-expressions.go 
-match: false
-match: false
-regex: p[a-z]+ch
+true
+true
+peach
+[0 5]
+[peach ea]
+[0 5 1 3]
+[peach punch pinch]
+[peach punch]
+true
+p([a-z]+)ch
+a <fruit>
+a PEACH
+
+# For a complete reference on Go regular expressions check
+# the [`regexp`](http://golang.org/pkg/regexp/) package docs.