other_notes.md

lua programming

• starter code

  print("hello")
  
  a = 100 + 300
  print(a)
  
  b = function(c) return c*c end
  
  print(b(100))
  
  collectgarbage()
  -- string concat
  a =  'hello ' .. 'world!'
  print(a)
  
  t = {}
  t.abc = 10
  
  print(t.abc)
  print(t.def)
  
  arr = {1, 2, 3, 4, 5, 6}
  print(arr)
  

  for k, v in ipairs(t) do
    print(k, v)
  end
  
  for k, v in ipairs(arr) do
    print(k, v)
  end
  
  function func(x)
    return function(y)
      return x + y
    end
  end
  
  add1 = func(1)
  add10 = func(10)
  
  print(add1(10))
  print(add10(10))
  
  local x = 1
  while x <= 10 do
    print(x)
    x = x + 1
  end
  
  for x = 1, 5, 0.5 do
    print(x)
  end
  
  if 5 == 5 then
    print('5')
  elseif 1 == 1 then
    print('1')
  end
  
  io.write('enter something: ')
  line = io.read()
  print(line)
  
  -- open file
  f = io.open('file', 'w')
  f.write('hello world')
  f.close()
  
  vec = dofile('vec.lua')
  print(vec.norm(1, 1))
  
  pcall(print, 'hello')
  
  print(math.sqrt(100))

  2017-1-11

perl programming beginner

• some starter code

  use strict;
  use warnings;
  use diagnostics;
  use feature 'say';
  use feature 'switch';
  
  print "hello world\n";
  
  my $name = 'Joseph';
  my ($age, $street) = (23, '123 main street');
  my $info = "$name lives on $street\n";
  $info = qq{$name lives on $street\n};
  print $info;
  
  my $random_stuff = <<"END";
  This is just some
  random stuff
  that does not make any sense
  END

  say $random_stuff;
  
  if ($age < 16) {
    say "you are young";
  } elsif ($age < 60) {
    say "you are ok";
  } else {
    say "you are old";
  }
  
  my $i = 0;
  while ($i < 10) {
    print "$i ";
    $i ++;
  }
  
  given ($age) {
    when ($age < 16) {
      say "cannot drive";
    }
    when ($age > 17) {
      say "can drive";
    }
  }
  
  my @stuff = ('Joseph', '123 main street', 23, 6.25);
  for my $s (@stuff) {
    say $s;
  }
  foreach my $s (@stuff) {
    say $s;
  }
  
  say @stuff[0, 1];
  say scalar @stuff;
  say join(", ", @stuff);
  
  my %new_stuff = (
    'Stuff1'=> 'weird',
    'Stuff2'=> 'cool',
    'Stuff3'=> 'non sense'
  );
  say %new_stuff;
  
  sub get_random_max {
    my ($max_num) = @_;
    $max_num ||= 11;
    return int(rand $max_num);
  }
  
  say get_random_max(100);
  
  sub sum {
    my ($n1, $n2) = @_;
    return $n1 + $n2;
  }
  
  say sum(10, 20);
  
  sub sum_many {
    my $sum = 0;
    foreach my $val (@_) {
      $sum += $val;
    }
    return $sum;
  }
  
  say sum_many(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

  2017-1-12

Markdown Math Formula

• markdown math formula

  $f(x) = x^2 + 2$
  
  $f'(x) = 2x$
  
  $x_{t+1} = x_t - \frac{f(x)}{f'(x)}$

  2017-1-26

VBScript on Windows

• hello world program

  Option Explicit
  On Error Resume Next
  
  MsgBox "hello!!"

  • copy files using object fso

  Option Explicit
  ' On Error Resume Next
  
  Dim fso, folder, folderName, target
  
  Set fso = CreateObject("Scripting.FileSystemObject")
  Set target = fso.GetFolder("D:\workspace\exercise")
  folderName = "D:\workspace\copy"
  
  If (Not fso.FolderExists(folderName)) Then
    WScript.Echo "Creating folder" & folder & "..."
    fso.CreateFolder(folder)
  End If
  
  Dim file
  For Each file in target.Files
    file.Copy "D:\workspace\copy\"
  Next

  2017-1-30

Sqlite Select Group by

SELECT col FROM table GROUP BY col

2017-2-1