First iteration of slides for T-DOSE

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+*          What's cool about CHICKEN 5?
+#+STARTUP: inlineimages
+                   [[./chicken-logo.png]]
+
+
+**                   Peter Bex
+
+                    T-DOSE
+                   Eindhoven
+                May 11th, 2019
+
+* Who am I?
+
+** Peter Bex
+
+*** Work: codeyellow.nl  
+  We're hiring! Talk to me or Burhan later
+*** Freelancing on the side: pebble-software.nl
+*** Blog (mostly about CHICKEN): more-magic.net
+
+*** Fell in love with Scheme at university, ~2002
+*** CHICKEN user since 2003
+  eggs: postgresql, spiffy, http-client, ...
+*** CHICKEN core contributor since late 2009
+  regex engine, macros, garbage collector, ...
+* Scheme: intro
+ Dialect of /LISP/, a functional language (impure)
+ LISP is from 1958, Scheme 1975; still here!
+
+ Other Lisps: Common Lisp, Emacs Lisp, Clojure, ..
+ Not for everyone -> Love it or hate it!
+#+BEGIN_SRC scheme
+ (display "Hello, world!\n") ;; Obligatory
+
+ (define (fib n) ;; Fibonacci, because why not
+   (if (<= n 2)
+       1
+       (+ (fib (- n 1))
+          (fib (- n 2)))))
+#+END_SRC
+
+* Scheme: philosophy
+
+** Super minimal but powerful language
+ User is an equal to the makers of the language
+
+ Very few things *need* "special" support
+
+ Advantages of small extensible core:
+ - ease of understanding (fits in your head)
+ - embeddability
+ - facilitates experimental implementations
+ - timelessness; e.g. classes can just be a
+   library. C => C++/ObjC, Pascal => Object Pascal
+   but Scheme => Scheme
+* Scheme superpowers: macros
+
+** Fully hygienic macro system
+#+BEGIN_SRC scheme
+ (define-syntax swap!
+   (syntax-rules ()
+     ((_ a b) (let ((x a))
+                (set! a b)
+                (set! b x)))))
+
+ ;; Does the right thing, i.e. print 2:
+ (let ((x 1) (y 2))
+   (swap! x y)
+   (display y))
+#+END_SRC
+
+* Scheme superpowers: closures
+
+** Lexical scoping
+
+ Gives us *closures* (now ubiquitous; first LISP)
+#+BEGIN_SRC scheme
+ (define (make-counter)
+   (let ((val 0))
+     (lambda () ; Anonymous fn, closes over "val"
+       (set! val (+ val 1))
+       val)))
+ (define c (make-counter))
+ (c) ; 1
+ (c) ; 2
+#+END_SRC
+
+* Scheme superpowers: continuations
+
+** Continuations
+
+ Can be used to implement exceptions, co-routines,
+ serialize full program state, etc etc
+
+ Tail calls "for free" [Lambda the Ultimate Goto]
+ Tail recursion is /required by the spec/!
+ Bad implementations often conveniently ignore it
+
+ Deep recursion is okay; just eats up more heap
+
+ See also Stackless Python
+
+* Scheme superpowers: numeric tower
+
+** Numeric tower
+
+Systematic support for /all the numbers/
+Spec defines system, subset is allowed (see later)
+#+BEGIN_SRC scheme
+1           ;; exact integer
+0.5         ;; inexact real number
+1/2         ;; exact rational number
+1+2i        ;; exact complex number
+0.5+0.25i   ;; inexact complex number
+1/2+3/4i    ;; ALSO an exact complex number
+(+ 3/4 1/2) ;; yes, this returns 5/4
+#+END_SRC
+
+* CHICKEN: intro
+
+ /Implementation/ of Scheme (one of the few
+ serious ones)
+
+ Based on Henry Baker's [Cheney On The MTA] idea:
+ Use C stack for initial heap (nursery)
+
+ Been around since 2000.
+
+ Compiles to C.  Uses GCC, clang, ... to generate
+ machine code, so: very portable
+
+ *Great* community! Produced lots of libraries
+
+* CHICKEN: C interop
+
+ Interop with C is trivial; just drop down to it
+#+BEGIN_SRC scheme
+ (import (chicken foreign))
+
+ (foreign-declare "#include <math.h>")
+
+ (define twice-exp
+   (foreign-lambda* double ((double x))
+     "double result = exp(x);"
+     "C_return(result * 2.0);"))
+
+ (display (twice-exp 5)) ;; 296.826318205153
+#+END_SRC
+
+* CHICKEN 5: Overhaul of module system
+
+** Most user-visible change
+ Old CHICKENs had such memorable module names as
+ "utils" and "extras"... Most was in "chicken"
+
+ Hard to remember, inconsistent
+
+ Large libraries (but few imports needed)
+
+** Naming scheme (haha) inspired by R7RS
+ (scheme base) => (chicken base)
+ (scheme file) => (chicken file) etc
+ others: (chicken posix), (chicken foreign) etc
+* CHICKEN 5: Overhaul of module system; examples
+
+** A few good examples to give you an idea:
+ "sort" procedure in CHICKEN 4: data-structures
+ "sort" procedure in CHICKEN 5: (chicken sort)
+
+ "symbol-append" in CHICKEN 4: library?! chicken
+ "symbol-append" in CHICKEN 5: (chicken base)
+
+ "->string" in CHICKEN 4: data-structures
+ "->string" in CHICKEN 5: (chicken string)
+
+ "read-line" in CHICKEN 4: extras
+ "read-line" in CHICKEN 5: (chicken io)
+
+* CHICKEN 5: Numeric tower; old situation
+
+** Older CHICKENs had only "fixnums" and "flonums"
+
+*** Quite fast (compile to ~standard C float/int)
+
+*** Never felt very "complete" or "serious" to me
+ LISP/Scheme is awesome, dammit!
+
+*** Issues with C FFI
+ Only 62 (or 30) bits available for ints; 
+ precision loss
+
+** So, I made it my mission to fix this
+
+* CHICKEN 5: Numeric tower; new situation
+
+** Most important: large integers ("bignums")
+ C FFI finally supports /size_t/ and friends!
+
+** Exact rational numbers are nice too;
+ Calculations will always be exact
+
+** Complex numbers mostly for completeness
+ Not that many use-cases(?)
+
+** Pretty fast, but a bit slower than CHICKEN 4
+ Mostly due to pre-allocation.  Working on it!
+*** Enough self-promotion, on to other features
+* CHICKEN 5: static compilation
+
+** Great for binary deployment / distribution
+ No need to mess around with "virtualenvs" etc
+
+ Just plop the binary onto a server; done
+
+ Killer feature of Go, for example
+
+** CHICKEN always supported static compilation!
+ Sucked for eggs (nobody tests it)
+
+** Solution: declarative egg format
+ Makes it harder to mess up
+* CHICKEN 5: static compilation; old situation
+
+** Old (imperative) .setup-file format:
+#+BEGIN_SRC scheme
+ (compile -s ncurses.scm -L -lncurses -j ncurses)
+ (compile -s ncurses.import.scm)
+ (compile -c ncurses.scm -L -lncurses 
+          -unit ncurses) ; Almost nobody did this
+
+ (install-extension
+  'ncurses
+  '("ncurses.o" "ncurses.so" "ncurses.import.so")
+  '((version "1.6")
+    (static "ncurses.o"))) ; And this
+#+END_SRC scheme
+
+* CHICKEN 5: static compilation; new situation
+
+** New (declarative) .egg-file format:
+#+BEGIN_SRC scheme
+ ((synopsis "An interface to ncurses")
+  (category ui)
+  (license "BSD")
+  (build-dependencies bind)
+  (author "felix winkelmann")
+  (maintainer "The CHICKEN Team")
+  ;; This replaces the .setup file:
+  (components (extension ncurses
+                (link-options -L -lncurses))))
+#+END_SRC scheme
+
+* CHICKEN 5: declarative egg files; sh scripts
+
+** Generates sh scripts (batch files on Windows)
+#+BEGIN_SRC sh
+ chicken-do ncurses.so ncurses.import.scm : \
+  ncurses.scm ncurses.egg : \
+  csc -host -J -s -setup-mode -I . -C -I. \
+  -L -lncurses ncurses.scm -o ncurses.so
+
+ chicken-do ncurses.static.o ncurses.link : \
+  ncurses.scm ncurses.egg : \
+  csc -setup-mode -static -I . -emit-link-file \
+  ncurses.link -host -c -unit ncurses \
+  -C -I. ncurses.scm -o ncurses.static.o
+#+END_SRC
+
+* CHICKEN 5: declarative egg files; advantages
+
+** Advantages of declarative format
+
+ Static linking is *always* built-in
+
+ Cross-compilation is made easier
+
+ Support for new features can be retroactively
+ added to all eggs
+
+ Security
+
+ Less typing!
+
+* CHICKEN 5: binary reproducible builds
+
+** Both CHICKEN itself and eggs
+
+ Made output of Scheme to C conversion stable
+ C to binary is left to the C tool chain
+
+** Gives us verifiability
+
+ See also [reproducible-builds.org]
+
+** Nice bonus: Faster builds with ccache
+
+ Generated C is identical!
+
+* Final words
+
+** Most important eggs have already been ported!
+ CHICKEN 5 is recommended for new code
+
+** Start porting your CHICKEN 4 code
+ How-to guide: wiki.call-cc.org/porting-c4-to-c5
+
+** CHICKEN 5.1 is upcoming
+*** Bugfixes, perf improvements, cleanups
+ The usual
+
+*** New "c-objects" declaration in egg files
+ Some eggs will require 5.1!
+
+* Thank you!
+                    [[./chicken-logo.png]]
+
+**                 CHICKEN website
+                   call-cc.org
+
+**                   IRC channel
+              #chicken on Freenode
+
+**                     My blog
+                 more-magic.net
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