Good practice - 1 • My Notes

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)
        }
    }
}