sreenichelikam-hpe / fun-with-go

A personal journey of fun and experiments with the Go language

fun-with-go

A personal journey of fun and experiments with the Go language.

Following are some of the functions, variables and commands that I am personally using along my journey with Go.

functions and vars

• len(v Type) int
• bufio.NewScanner(r io.Reader) *Scanner
• bufio: (s *Scanner).Scan() bool
• bufio: (s *Scanner).Text() string
• fmt.Println(a ...interface{}) (n int, err error)
• fmt.Sprintf(format string, a ...interface{}) string
• strings.Join(elems []string, sep string) string
• os.Args []string
• os.Stdin NewFile(uintptr(syscall.Stdin), "/dev/stdin")
• runtime.NumCPU() int
• time.Now() Time
• time.Since(t Time) Duration

keywords

• break
• case
• chan
• const // example: const World = "世界"
• default
• defer
• else
• for
• func
• go
• if
• import
• interface
• map
• package
• range
• return
• select
• struct
• switch
• type // example: switch v := i.(type)
• var

keywords pool

• goto
• fallthrough
• continue

tools

• go [command] [arguments]
• go build [packages]
• go doc [pkg] [methodOrField]
• go fmt [filename]
• go get [packages] (-v:verbose)
• go help [keyword]
• go run [filename]
• go test -bench=. [filename]
• go version

definitions

• pointers
  • a pointer holds the memory address of a value
  • the & operator generates a pointer to its operand
  • the * operator denotes a pointer's underlying value

some common conversion characters in format strings

%d	int in decimal
%x, %o, %b	int in hex, oct, bin
%f, %g, %e	float
%t	bool
%c	rune
%s	string
%q	quoted string, rune
%v	any value
%T	type
%%	literal percent

helpful custom programs

• generate random number with crypto/rand based seed

nuances

• switch - see switch condition
• switch evaluation order - see evaluation in case
• switch with no condition - see no condition
• pointers - unerstand pointer, &, *
• struct pointers - see struct field change via pointer
• a slice consists of a pointer to the array, the length of the segment, and its capacity
• slice length & capacity - see how underlying array capacity changes when array elements are removed from front of array
• create slice with make - reinforce understanding of how removing array elements from beginning affect underlying array capacity
• pointer receivers
• pointers & functions
• methods and pointer indirection - methods with pointer receivers take either a value (as a convenience) or a pointer
• therefore method pointer receivers can modify the received value even if it was passed as a value instead of a pointer
• all methods on a given type should have either value or pointer receivers, but not a mixture of both
• a value of interface type can hold any value that implements those methods
• an interface value holds a value of a specific underlying concrete type
• if the concrete value inside the interface itself is nil, the method will be called with a nil receiver
• calling a method on a nil interface is a run-time error - there has to be some type with a concrete method assigned to the interface value
• an empty interface may hold values of any type
• type assertion provides access to an interface value's underlying concrete value
• type assertion syntax is similar to that of reading from a map
• the error type is a built-in interface similar to fmt.Stringer
• as with fmt.Stringer, the fmt package looks for the error interface when printing values
• only the sender should close a channel, never the receiver
• fibonacci with scalar array and channels - practice
• closing a channel is only necessary when the receiver must be told there are no more values coming, such as to terminate a range loop

type Stringer interface {
    String() string
}
type error interface {
    Error() string
}

• there are many implementations of the io.Reader interface, including files, network connections, compressors, ciphers, and others

exercise solutions

• custom Sqrt function
• implement Pic
• implement WordCount
• implement Fibonacci sequence using closure
• implement stringer
• errors
• errors
• implement Read that emits 'A'
• implement rot13Reader
• implement Image
• implement equivalent binary trees
• implement web crawler

ref blog articles

• Go Slices: usage and internals