Notes on Go Structure Tags

Go has a feature to create a user-defined type with struct. Go also allows the program to specify meta-information with structure field.
This meta-information is called Tags. A tag usually helps in packaging/unpacking a user-defined type structure.

  package main

  import (
      "encoding/json"
      "fmt"
  )

  type Test struct {
      // json tags indicate the key name to use in json data
      Name    string `json:"myname"`
      Country string `json:"region"`
  }

  func main() {
      // The order of json need not match the order of structure fields.
      p := map[string]string{"region": "earth", "myname": "hello"}

      marshalled, err := json.Marshal(p)
      fmt.Println(marshalled, err)

      // get the var back from marshalled data
      var m Test
      json.Unmarshal(marshalled, &m)
      fmt.Printf("name=%v\n", m.Name)
      fmt.Printf("name=%v\n", m.Country)
  }

Why should I use json tags

  • The benefit of json tags is the flexibility to marshal with either a JSON or a struct.
  • JSON input for marshaling is convenient and flexible with elements ordering.

Reference

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Adding Query Params to a URL in Ruby with HTTP

The clearest example was in a StackOverflow post

require 'uri'

def add_param(url, param_name, param_value)
 uri = URI(url)
 params = URI.decode_www_form(uri.query || "") << [param_name, param_value]
 uri.query = URI.encode_www_form(params)
 uri.to_s
end

You can pass a map of params key & values and get expected URL.

Another example

 # prepare params.
 params = { 'id' => '12' }

 path = 'http://localhost/'
 uri = URI(path)

 uri.query = URI.encode_www_form(params)

Output

http://localhost?id=12

Reference

How to Change View of Coding Block in WordPress?

Problem

Many times a good WordPress theme does not render code properly. There are problems like too big font making it harder to read the text. I use StackEdit to prepare posts and publish to my blog.

Solution

There is a way to solve this problem with custom CSS.

Description

The posting source is in Markdown. StackEdit translates MarkDown to HTML and posts to the destination. There is not much I could do with the Markdown. However, the theme on the WordPress blog allows me to set a CSS for particular content.
The code blocks are translated to pre blocks in the HTML. So adding a custom rendering for pre block should fix the problem.
I found a CSS snippet from https://wp-mix.com/css-style-pre-tags/.

pre {
	box-sizing: border-box;
	width: 100%;
	padding: 0;
	margin: 0;
	overflow: auto;
	overflow-y: hidden;
	font-size: 12px;
	line-height: 20px;
	background: #efefef;
	border: 1px solid #777;
	background: url('lines.png') repeat 0 0;
	padding: 10px;
	color: #333;
}

Another good reference is https://perishablepress.com/perfect-pre-tags/

This made the code look much much better.

Update

One More Reason to Avoid Ruby Language

Ruby is type unsafe language but it goes a step further and avoids checking dynamically too.

Consider this code

x = :abc
if x == 'abc'
  puts "Symbol and String are two different classes"
else
  puts x.class, 'abc'.class
end

# puts can print a symbol and string alike.
puts x

My Complaints

  • I’m new to Ruby. How could Ruby let a Symbol and String compare, in spite of being aware of their types? Like Python, it can throw an error.
  • How can puts print a Symbol as good as a String

References

C++: Max Product in a Matrix witout Backtrack

Problem

Given a matrix, find the path from top left to bottom right with the greatest product by moving only down and right.

The code is in C++.
The only moves allowed are down and right. The solution works for positive numbers.

Reference

Written with StackEdit.