seven-more-languages-in-seven-weeks/slides/factor.org

#+TITLE: Seven More Languages in Seven Weeks
#+BEAMER_HEADER: \subtitle{Factor}
#+BEAMER_HEADER: \institute[INST]{Extreme Tech Seminar}
#+AUTHOR: Correl Roush
#+EMAIL: correl@gmail.com
#+DATE: January 27, 2016
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* Introduction

** Introduction

*** Factor                                                          :BMCOL:
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FACTOR
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A stack-based, concatenative programming language
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*** Mr. Miyagi                                                      :BMCOL:
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[[file:Mr_Miyagi.jpg]]
* Day 1
** Day 1: Stack On, Stack Off
- Installing Factor
- Using the REPL
- Basic Syntax & Data Types
- Stack Shuffling
- Combinators
** Getting Stacked
#+BEGIN_SRC factor
  "Hello, world" print
  ! Hello, world

  "same" length "diff" length = .
  ! t
#+END_SRC
** Data Types
- Booleans ::
     ~t~ or ~f~
- Sequences ::
  - Lists :: ~{ 4 3 2 1 }~
  - Maps :: ~{ { "one" 1 } { "two" 2 } { "three" 3 } }~
- Quotations ::
     ~[ 42 + ]~
** Conditionals
Conditionals take quotations as branching arguments

#+BEGIN_SRC factor
  10 0 > [ "pos" ] [ "neg" ] if .
  ! pos
  -5 0 > [ "pos" ] [ "neg" ] if .
  ! neg
#+END_SRC
** Stack Shuffling
- dup :: Duplicate a value on the stack
- drop :: Drop the top value from the stack
- nip :: Drop the second value
- swap :: Swap two values
- over :: Duplicates the second value over to the top
- rot :: Rotate the top 3 values on the stack
** Combinators
- ~bi~, ~bi@~, ~bi*~
- ~tri~, ~tri@~, ~tri*~
- ~dip~, ~keep~

#+BEGIN_SRC factor
  44.50 [ 0.05 * ] [ 0.09975 * ] bi
  ! 2.225
  ! 4.438875

  44.50 22.50 [ 0.05 * ] bi@
  ! 2.225
  ! 1.125

  44.50 22.50 [ 0.05 * ] [ 0.09975 * ] bi*
  ! 2.225
  ! 2.244375
#+END_SRC
** Exercises
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Exercises
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*** Easy                                                             :B_note:
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:BEAMER_env: note
:END:
 Using only * and + , how would you calculate 3^2 + 4^2 with
 Factor?

#+BEGIN_SRC factor
  4 dup * 3 dup * + .
#+END_SRC

 Enter USE: math.functions in the Listener. Now, with sq and sqrt ,
 calculate the square root of 3^2 + 4^2 .

#+BEGIN_SRC factor
  3 sq 4 sq + sqrt .
#+END_SRC

#+BEGIN_SRC factor
  1 2
  over swap
#+END_SRC

#+BEGIN_SRC factor
  USE: ascii

  "Correl" "Hello, " swap append >upper .
#+END_SRC
*** Medium                                                         :B_note:
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* Day 2
** Day 2: Painting the Fence
- Defining Words
- Vocabularies
- Unit Tests
- Interview with Slava Pestov
** Defining Words
#+BEGIN_SRC factor
  : add-42 ( x -- y ) 42 + ;

  : sum ( seq -- n ) 0 [ + ] reduce ;

  : first-two ( seq -- a b ) [ first ] [ second ] bi ;
#+END_SRC
** Vocabularies
Words are organized into vocabularies, which are similar to packages,
modules, or namespaces in other languages.
** Unit Tests
Factor includes a unit testing vocabulary (~tools.test~), which is
useful for ensuring correctness of your code, and also experimenting
with the language.

#+BEGIN_SRC factor
  USING: examples.greeter tools.test ;
  IN: examples.greeter.tests

  { "Hello, Test" } [ "Test" greeting ] unit-test
#+END_SRC
** Interview with Slava Pestov
#+BEGIN_QUOTE
I decided to write my own language, though, because I wanted something
really simple, and also just because it would be fun.
#+END_QUOTE

** Exercises
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Exercises
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* Day 3
** Day 3: Balancing on the Boat
- Tuples
- Pipelining with Higher-Order Words
** Tuples
1. Defining
   #+BEGIN_SRC factor
     TUPLE: name slot ... ;
   #+END_SRC
2. Accessing and Modifying
   - =slot>>=
   - =>>slot=
   - =change-slot=
3. Creating
   - =boa= (/By Order of Arguments/)
   - =T{ name { slot value } ... }=
** Higher-Order Words
#+BEGIN_SRC factor
  CONSTANT: gst-rate 0.05
  CONSTANT: pst-rate 0.09975

  : gst-pst ( price -- taxes ) [ gst-rate * ] [ pst-rate * ] bi + ;

  : taxes ( checkout taxes-calc -- taxes )
      [ dup base-price>> ] dip
      call >>taxes ; inline
#+END_SRC

The =inline= keyword is necessary, as the =taxes= word takes
quotations as parameters.
* Wrapping Up
** Wrapping Up
*** Strengths
- Simple syntax
- Easy function composition
- Batteries included
*** Weaknesses
- Learning curve
- Small community
- Limited resources
** Final Thoughts
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Final Thoughts
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