Good practice - 1

Strings

Change a character

• How to change a character in a string

  str:="hello"
  c:=[]byte(s)
  c[0]=’c’
  s2:= string(c) // s2 == "cello"
  

Substring

• How to take a part(substring) of a string str

substr := str[n:m]

for-loop

• How to loop over a string str with for or for-range:

// gives only the bytes:
for i:=0; i < len(str); i++ {
     … = str[i]
}
// gives the Unicode characters:
for ix, ch := range str {
    // …
} 

bytes of str

• Number of bytes in a string str

  len(str)
  

• Number of characters in a string str

utf8.RuneCountInString(str) // FATEST 
len([]int(str))

Concat strings

• Best performance with byte buffer

  var buffer bytes.Buffer
  for {
      if s, ok := getNextString(); ok { //method getNextString() not shown here
          buffer.WriteString(s)
      } else {
          break
      }
  }
  

• Simple way

strings.Join()

Command-line args

• Use flag and os package

Array

Cut the last element

• How to cut the last element of an array or slice line

line = line[:len(line)-1]

Loop over the array

• for-loop

for i:=0; i < len(arr); i++ {
    … = arr[i]
}

• for range

for ix, value := range arr {
    …
}

Search value in 2D array

found := false
Found: for row := range arr2Dim {
    for column := range arr2Dim[row] {
        if arr2Dim[row][column] == V {
            found = true
            break Found
        }
    }
}

Reverse

func ReverseInts(s []int) {
    first := 0
    last := len(s) - 1
    for first < last {
        s[first], s[last] = s[last], s[first]
        first++
        last--
    }
}

Maps

loop with range

for key, value := range map1 {
… 
}

Test if key exists

val1, isPresent = map1[key1]
// which gives: val or zero-value, true or false

Deleting a key in a map

delete(map1, key1)

Interface

Test if a value implements Stringer

if v, ok := v.(Stringer); ok {
    fmt.Printf("implements String(): %s\n", v.String());
}

A type classifier:

func classifier(items ...interface{}) {
    for i, x := range items {
        switch x.(type) {
            case bool: fmt.Printf("param #%d is a bool\n", i)
            case float64: fmt.Printf("param #%d is a float64\n", i)
            case int, int64: fmt.Printf("param #%d is an int\n", i)
            case nil: fmt.Printf("param #%d is nil\n", i)
            case string: fmt.Printf("param #%d is a string\n", i)
            default: fmt.Printf("param #%d’s type is unknown\n", i)
        }
    }
}