Started new .travis.yml - www - Unnamed repository; edit this file 'description' to name the repository.

commit 6b282c7b3614bf0b28cccf066dbc93c934ed8e47
parent 65f7a554be09fd8b603892825b86fe032c4fd00b
Author: Georges Dupéron <georges.duperon@gmail.com>
Date:   Wed, 21 Jun 2017 19:20:58 +0200

Started new .travis.yml

Diffstat:
M .travis.yml  | 109 +++++++++++++++++++++----------------------------------------------------------
M scribblings/tr.scrbl  | 7906 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------

2 files changed, 7332 insertions(+), 683 deletions(-)
diff --git a/.travis.yml b/.travis.yml
@@ -1,95 +1,42 @@
 language: c
-
-# Based from: https://github.com/greghendershott/travis-racket
-
-# Optional: Remove to use Travis CI's older infrastructure.
 sudo: false
 
 env:
   global:
-    # Supply a global RACKET_DIR environment variable. This is where
-    # Racket will be installed. A good idea is to use ~/racket because
-    # that doesn't require sudo to install and is therefore compatible
-    # with Travis CI's newer container infrastructure.
+    # RACKET_DIR is an argument to install-racket.sh
     - RACKET_DIR=~/racket
+    - PATH="$RACKET_DIR/bin:$PATH"
   matrix:
-    # Supply at least one RACKET_VERSION environment variable. This is
-    # used by the install-racket.sh script (run at before_install,
-    # below) to select the version of Racket to download and install.
-    #
-    # Supply more than one RACKET_VERSION (as in the example below) to
-    # create a Travis-CI build matrix to test against multiple Racket
-    # versions.
-    #- RACKET_VERSION=6.0
-    #- RACKET_VERSION=6.1
-    #- RACKET_VERSION=6.1.1
-    #- RACKET_VERSION=6.2
-    #- RACKET_VERSION=6.3
-    #- RACKET_VERSION=6.4
-    #- RACKET_VERSION=6.5
-    #- RACKET_VERSION=6.6
-    #- RACKET_VERSION=6.7
-    #- RACKET_VERSION=6.8
     - RACKET_VERSION=6.9 DEPLOY=true
-    #- RACKET_VERSION=HEAD
 
 cache:
   directories:
     - $HOME/.racket
 
-addons:
-  apt:
-    packages:
-    - texlive-latex-base
-    - texlive-fonts-extra
-    - texlive-fonts-recommended
-    - texlive-latex-extra
-    - latex-xcolor
-    #- graphviz
-
-matrix:
-  allow_failures:
-#   - env: RACKET_VERSION=HEAD
-  fast_finish: true
-
 before_install:
-- git clone https://github.com/greghendershott/travis-racket.git ~/travis-racket
-- cat ~/travis-racket/install-racket.sh | bash # pipe to bash not sh!
-- export PATH="${RACKET_DIR}/bin:${PATH}" #install-racket.sh can't set for us
-- echo "LaTeX extra packages:"
-- latex_home=$(kpsewhich -var-value=TEXMFHOME)
-- curl -L -o newunicodechar.ins http://mirrors.ctan.org/macros/latex/contrib/newunicodechar/newunicodechar.ins
-- curl -L -o newunicodechar.dtx http://mirrors.ctan.org/macros/latex/contrib/newunicodechar/newunicodechar.dtx
-- latex newunicodechar.ins
-- mkdir -p "$latex_home/tex/latex/newunicodechar"
-- mv newunicodechar.sty "$latex_home/tex/latex/newunicodechar"
-
-install:
- - raco pkg remove -j 2 --no-trash phc-thesis || true # Attempt to remove already cached version.
- - raco pkg update -j 2 --all --scope user
-# - raco pkg install -j 2 --deps search-auto phc-adt # Help a bit by populating the cache.
- - raco pkg install -j 2 --deps search-auto
-# --no-setup
-# - (while ! test -e ~/done.txt; do sleep 10; echo -n '.'; done) & raco setup -v -j 2 --pkgs phc-thesis && touch ~/done.txt
-
-before_script:
-
-# Here supply steps such as raco make, raco test, etc.  You can run
-# `raco pkg install --deps search-auto` to install any required
-# packages without it getting stuck on a confirmation prompt.
-script:
- echo "."
- - raco test -x -p phc-thesis
- - raco setup --check-pkg-deps --no-zo --no-launcher --no-install --no-post-install --no-docs --pkgs phc-thesis
- - rm -fr doc/
- - raco scribble --dest doc/phc-thesis --html --dest-name index ++main-xref-in --redirect-main https://docs.racket-lang.org/ --redirect https://docs.racket-lang.org/ scribblings/phc-thesis.scrbl
- - make
- - if test "x${DEPLOY:-}" = "xtrue"; then sh ./auto-push-gh-pages.sh; fi
- - du -hs ~/.racket
-
-#after_success:
-# - raco pkg install --deps search-auto cover cover-coveralls
-# - raco cover -b -f coveralls -d $TRAVIS_BUILD_DIR/coverage .
-
-#after_success:
-# - sh ./auto-push-master.sh
+- curl -L https://raw.githubusercontent.com/greghendershott/travis-racket/master/install-racket.sh | bash
+# - if $COV; then raco pkg install --deps search-auto doc-coverage cover cover-codecov; fi # or cover-coveralls
+
+jobs:
+  include:
+    - stage: phase1
+      install:
+      - echo hello > ~/.racket/hello
+      - echo "$TRAVIS_BUILD_ID" > ~/.racket/travis_build_id
+      script:
+      - ls -la $HOME
+      - tree ~/.racket
+    - stage: phase2
+      addons:
+        apt:
+          packages:
+          - texlive-latex-base
+      install:
+      - echo bye > ~/.racket/hello
+      - cat ~/.racket/hello
+      - if "$TRAVIS_BUILD_ID" != `cat ~/.racket/travis_build_id`; then travis_terminate 1; fi
+      script:
+      - ls -la $HOME
+      - tree ~/.racket
+      - mv ~/.racket ~/.racket-discard
+      - mkdir ~/.racket # clear the cache
diff --git a/scribblings/tr.scrbl b/scribblings/tr.scrbl
@@ -1,603 +1,7306 @@
-#lang scribble/manual
+#reader(lib"read.ss""wxme")WXME0108 ## 
+#|
+   This file uses the GRacket editor format.
+   Open this file in DrRacket version 6.9.0.4 or later to read it.
 
-@require["util.rkt"
-         (for-label (only-meta-in 0 typed/racket))
-         scribble/example
-         racket/string]
-@(use-mathjax)
+   Most likely, it was created by saving a program in DrRacket,
+   and it probably contains a program with non-text elements
+   (such as images or comment boxes).
 
-@(define tr-eval (make-eval-factory '(typed/racket)))
-
-@title[#:style (with-html5 manual-doc-style)
-       #:version (version-text)
-       #:tag "tr-chap"]{@|Typedracket|}
-
-We start this section with some history: Lisp, @emph{the} language with lots
-of parentheses, shortly following Fortran as one of the first high-level
-programming languages, was initially designed between 1956 and 1958, and
-subsequently implemented@~cite["McCarthyHistoryLisp"]. Dialects of Lisp
-generally support a variety of programming paradigms, including (but not
-limited to) functional programming and object-oriented programming (e.g. via
-CLOS, the Common Lisp Object System). One of the the most proeminent aspects
-of Lisp is homoiconicity, the fact that programs and data structures look the
-same. This enables programs to easily manipulate other programs, and led to
-the extensive use of macros. Uses of macros usually look like function
-applications, but, instead of invoking a target function at run-time, a macro
-will perform some computation at compile-time, and expand to some new code,
-which is injected as a replacement of the macro's use.
-
-The two main dialects of Lisp are Common Lisp and Scheme. Scheme follows a
-minimalist philosophy, where a small core is
-standardised@~cite["r5rs" "r6rs" "r7rs"] and subsequently extended via macros
-and additional function definitions.
-
-Racket, formerly named PLT Scheme, started as a Scheme implementation. Racket
-evolved, and the Racket Manifesto@~cite["racketmanifesto"] presents it as a
-``programming-language programming language'', a language which helps with the
-creation of small linguistic extensions as well as entirely new languages. The
-Racket ecosystem features many languages covering many paradigms:
-
-@itemlist[
- @item{The @racketmodname[racket/base] language is a full-featured programming
-  language which mostly encourages functional programming.}
- @item{@racketmodname[racket/class] implements
-  @seclink["classes" #:doc '(lib "scribblings/guide/guide.scrbl")]{an
-   object-oriented system}, implemented atop @racketmodname[racket/base] using
-  macros, and can be used along with the rest of the @racketmodname[racket/base]
-  language.}
- @item{@racketmodname[racklog] is a logic programming language in the style of
-  prolog. The Racket ecosystem also includes an implementation of
-  @racketmodname[datalog].}
- @item{@seclink["top" #:doc '(lib "scribblings/scribble/scribble.scrbl")]{
-   Scribble} can be seen as an alternative to @|LaTeX|, and is used to create
-  the @seclink["top" #:doc '(lib "scribblings/main/start.scrbl")]{Racket
-   documentation}. It also supports literate programming, by embedding chunks of
-  code in the document which are then aggregated together. This thesis is
-  in fact written using Scribble.}
- @item{@racketmodname[slideshow] is a @deftech{DSL} (domain-specific language)
-  for the creation of presentations, and can be thought as an alternative to
-  Beamer and SliTeX.}
- @item{@racketmodname[r5rs] and @racketmodname[r6rs] are implementations of
-  the corresponding scheme standards.}
- @item{@seclink["top" #:doc '(lib "redex/redex.scrbl")]{Redex} is a
-  @usetech{DSL} which allows the specification of reduction
-  semantics for programming languages. It features tools to explore and test
-  the defined semantics.}
- @item{@|Typedracket|@~cite["tobin-hochstadt_design_2008"
-                            "tobin-hochstadt_typed_2010"] is a typed variant of
-  the main @racketmodname[racket] language. It is implemented as a macro which
-  takes over the whole body of the program. That macro fully expands all other
-  macros in the program, and then typechecks the expanded program.}
- @item{@seclink["top" #:doc '(lib "turnstile/scribblings/turnstile.scrbl")]{
-   @|Turnstile|} allows the creation of new typed languages. It takes a
-  different approach when compared to @|typedracket|, and threads the type
-  information through assignments and special forms, in order to be able to
-  typecheck the program during expansion, instead of doing so afterwards.}]
-
-In the remainder of this section, we will present the features of
-@|typedracket|'s type system, and then present formal semantics for a subset
-of those, namely the part which is relevant to our work.
-@other-doc['(lib "typed-racket/scribblings/ts-guide.scrbl")] and
-@other-doc['(lib "typed-racket/scribblings/ts-reference.scrbl")] provide good
-documentation for programmers who desire to use @|typedracket|; we will
-therefore keep our overview succinct and gloss over most details.
-
-@asection{
- @atitle{Overview of Typed Racket's type system}
-
- @asection{
-  @atitle{Simple primitive types}
-   
-  @Typedracket has types matching Racket's baggage of primitive values:
-  @racket[Number], @racket[Boolean], @racket[Char], @racket[String],
-  @racket[Void]@note{The @racket[Void] type contains only a single value,
-   @racket[#,(void)], and is equivalent to the @racketid[void] type in
-   @|C-language|. It is the equivalent of @racketid[unit] of @CAML and
-   @|haskell|, and is often used as the return type of functions which perform
-   side-effects. It should not be confused with @racket[Nothing], the bottom
-   type which is not inhabited by any value, and is similar to the type of
-   @|haskell|'s @racketid[undefined]. @racket[Nothing] can be used for example
-   as the type of functions which never return — in that way it is similar to
-   @|C-language|'s @tt["__attribute__ ((__noreturn__))"].} and so on.
-
-  @examples[#:label #f #:eval (tr-eval)
-            (ann #true Boolean)
-            243
-            "Hello world"
-            #\c
-            (code:comment "The void function produces the void value")
-            (code:comment "Void values on their own are not printed,")
-            (code:comment "so we place it in a list to make it visible.")
-            (list (void))]
-  
-  For numbers, @|typedracket| offers a ``numeric tower'' of
-  partially-overlapping types: @racket[Positive-Integer] is a subtype of
-  @racket[Integer], which is itself a subtype of @racket[Number]. @racket[Zero],
-  the type containing only the number 0, is a both a subtype of
-  @racket[Nonnegative-Integer] (numbers ≥ 0) and of @racket[Nonpositive-Integer]
-  (numbers ≤ 0).
-
-  @|Typedracket| also includes a singleton type for each primitive value of
-  these types: we already mentioned @racket[Zero], which is an alias of the
-  @racket[0] type. Every number, character, string and boolean value can be used
-  as a type, which is only inhabited by the same number, character, string or
-  boolean value. For example, @racket[243] belongs to the singleton type
-  @racket[243], which is a subtype of @racket[Positive-Integer].
-
-  @examples[#:label #f #:eval (tr-eval)
-            0
-            (ann 243 243)
-            #t]}
-
- @asection{
-  @atitle{Pairs and lists}
-
-  Pairs are the central data structure of most Lisp dialects. They are used to
-  build linked lists of pairs, terminated by @racket['()], the null element. The
-  null element has the type @racket[Null], while the pairs which build the list
-  have the type @racket[(Pairof _A _B)], where @racketid[_A] and @racketid[_B]
-  are replaced by the actual types for the first and second elements of the
-  pair. For example, the pair built using @racket[(cons 729 #true)], which
-  contains @racket[729] as its first element, and @racket[#true] as its second
-  element, has the type @racket[(Pairof Number Boolean)], or using the most
-  precise singleton types, @racket[(Pairof 729 #true)].
-
-  @examples[#:label #f #:eval (tr-eval)
-            (cons 729 #true)
-            '(729 . #true)]
-
-  Heterogeneous linked lists of fixed length can be given a precise type by
-  nesting the same number of pairs at the type level. For example, the list
-  built with @racket[(list 81 #true 'hello)] has the type
-  @racket[(List Number Boolean Symbol)], which is a shorthand for the type
-  @racket[(Pairof Number (Pairof Boolean (Pairof Symbol Null)))]. Lists in
-  @|typedracket| can thus be seen as the equivalent of a chain of nested
-  2-tuples in languages like @|CAML| or @|haskell|. The analog in
-  object-oriented languages with support for generics would be a class
-  @tt["Pair<A, B>"], where the generic type argument @racketid[B] could be
-  instantiated by another instance of @tt["Pair"], and so on.
-
-  @examples[#:label #f #:eval (tr-eval)
-            (cons 81 (cons #true (cons 'hello null)))
-            (ann (list 81 #true 'hello)
-                 (Pairof Number (Pairof Boolean (Pairof Symbol Null))))]
-
-  The type of variable-length homogeneous linked lists can be described using
-  the @racket[Listof] type operator. The type @racket[(Listof Integer)] is
-  equivalent to @racket[(Rec R (U (Pairof Integer R) Null))]. The @racket[Rec]
-  type operator describes @seclink["tr-presentation-recursive-types"]{recursive
-   types}, and @racket[U] describes @seclink["tr-presentation-unions"]{unions}.
-  Both of these features are described below, for now we will simply say that
-  the previously given type is a recursive type @racket[R], which can be a
-  @racket[(Pairof Integer R)] or @racket[Null] (to terminate the linked list).
-
-  @examples[#:label #f #:eval (tr-eval)
-            (ann (range 0 5) (Listof Number))]}
-
- @asection{
-  @atitle{Symbols}
-
-  Another of Racket's primitive datatypes is symbols. Symbols are interned
-  strings: two occurrences of a symbol produce values which are pointer-equal if
-  the symbols are equal (i.e. they represent the same string)@note{This is true
-   with the exception of symbols created with @racket[gensym] and the like.
-   @racket[gensym] produces a fresh symbol which is not interned, and therefore
-   different from all existing symbols, and different from all symbols created
-   in the future.}.
-
-  @|Typedracket| includes the @racket[Symbol] type, to which all symbols
-  belong. Additionally, there is a singleton type for each symbol: the type
-  @racket['foo] is only inhabited by the symbol @racket['foo].
-
-  @examples[#:label #f #:eval (tr-eval)
-            'foo]
-
-  Singleton types containing symbols can be seen as similar to constructors
-  without arguments in @|CAML| and @|haskell|, and as globally unique enum
-  values in object-oriented languages. The main difference resides in the scope
-  of the declaration: two constructor declarations with identical names in two
-  separate files will usually give distinct types and values. Similarly, when
-  using the ``type-safe enum'' design pattern, two otherwise identical
-  declarations of an enum will yield objects of different types. In contrast,
-  two uses of an interned symbols in Racket and @|typedracket| will produce
-  identical values and types. A way of seeing this is that symbols are similar
-  to constructors (in the functional programming sense) or enums which are
-  implicitly declared globally.
-
-  @examples[#:label #f #:eval (tr-eval)
-            (module m1 typed/racket
-              (define sym1 'foo)
-              (provide sym1))
-            (module m2 typed/racket
-              (define sym2 'foo)
-              (provide sym2))
-            (require 'm1 'm2)
-            (code:comment "The tow independent uses of 'foo are identical:")
-            (eq? sym1 sym2)]
- }
-  
- @asection{
-  @atitle[#:tag "tr-presentation-unions"]{Unions}
-
-  These singleton types may not seem very useful on their own. They can however
-  be combined together with union types, which are built using the @racket[U]
-  type operator.
-  
-  The union type @racket[(U 0 1 2)] is inhabited by the values @racket[0],
-  @racket[1] and @racket[2], and by no other value. The @racket[Boolean] type is
-  actually defined as @racket[(U #true #false)], i.e. the union of the singleton
-  types containing the @racket[#true] and @racket[#false] values, respectively.
-  The @racket[Nothing] type, which is not inhabited by any value, is defined as
-  the empty union @racket[(U)]. The type @racket[Any] is the top type, i.e. it
-  is a super-type of all other types, and can be seen as a large union including
-  all other types, including those which will be declared later or in other
-  units of code.
-
-  Unions of symbols are similar to variants which contain zero-argument
-  constructors, in @|CAML| or @|haskell|.
-
-  @examples[#:label #f #:eval (tr-eval)
-            (define v : (U 'foo 'bar) 'foo)
-            v
-            (set! v 'bar)
-            v
-            (code:comment "This throws an error at compile-time:")
-            (eval:error (set! v 'oops))]
-
-  A union such as @racket[(U 'ca (List 'cb Number) (List 'cc String Symbol))]
-  can be seen as roughly the equivalent of a variant with three constructors,
-  @racketid[ca], @racket[cb] and @racketid[cc], where the first has no
-  arguments, the second has one argument (a @racket[Number]), and the third has
-  two arguments (a @racket[String] and a @racket[Symbol]).
-
-  The main difference is that a symbol can be used as parts of several unions,
-  e.g. @racket[(U 'a 'b)] and @racket[(U 'b 'c)], while constructors can often
-  only be part of the variant used to declare them. Unions of symbols are in
-  this sense closer to @|CAML|'s so-called polymorphic
-  variants@~cite["minskyRealWorldOCaml"] than to regular variants.
-  
-  @examples[#:label #f #:eval (tr-eval)
-            (define-type my-variant (U 'ca
-                                       (List 'cb Number)
-                                       (List 'cc String Symbol)))
-            (define v₁ : my-variant 'ca)
-            (define v₂ : my-variant (list 'cb 2187))
-            (define v3 : my-variant (list 'cc "Hello" 'world))]
-
-  Finally, it is possible to mix different sorts of types within the same
-  union: the type @racket[(U 0 #true 'other)] is inhabited by the number
-  @racket[0], the boolean @racket[#true], and the symbol @racket['other].
-  Translating such an union to a language like @|CAML| could be done by
-  explicitly tagging each case of the union with a distinct constructor.
-
-  Implementation-wise, all values in the so-called ``untyped'' version of
-  Racket are tagged: a few bits within the value's representation are reserved
-  and used to encode the value's type. When considering the target of a pointer
-  in memory, Racket is therefore able to determine if the pointed-to value is a
-  number, boolean, string, symbol and so on. Typed Racket preserves these
-  run-time tags. They can then be used to detect the concrete type of a value
-  when its static type is a union. This detection is done simply by using
-  Racket's predicates: @racket[number?], @racket[string?], @racket[symbol?]
-  etc.}
-
- @asection{
-  @atitle{Intersections}
-
-  Intersections are the converse of unions: instead of allowing a mixture of
-  values of different types, an intersection type, described using the
-  @racket[∩] type operator, only allows values which belong to all types.
-
-  The intersection type @racket[(∩ Nonnegative-Integer Nonpositive-Integer)] is
-  the singleton type @racket[0]. The intersection of @racket[(U 'a 'b 'c)] and
-  @racket[(U 'b 'c 'd)] will be @racket[(U 'b 'c)], as @racket['b] and
-  @racket['c] belong to both unions.
-
-  @examples[
- #:label #f #:eval (tr-eval)
- (code:comment ":type shows the given type, or a simplified version of it")
- (:type (∩ (U 'a 'b 'c) (U 'b 'c 'd)))]
-  
-  @|Typedracket| is able to reduce some intersections such as those given above
-  at compile-time. However, in some cases, it is forced to keep the intersection
-  type as-is. For example, structs (@seclink["tr-presentation-structs"]{
-   describled below} can, using special properties, impersonate functions. This
-  mechanism is similar to PHP's @tt["__invoke"], the ability to overload
-  @tt["operator()"] in @|CPP|. @|Typedracket| does not handle these properties
-  (yet), and therefore cannot determine whether a given struct type also
-  impersonates a function or not. This means that the intersection
-  @racket[(∩ s (→ Number String))], where @racket[s] is a struct type, cannot be
-  reduced to @racket[Nothing], because @|typedracket| cannot determine whether
-  the struct @racket[s] can act as a function or not.
-
-  Another situation where @|typedracket| cannot reduce the intersection is when
-  intersecting two function types (@seclink["tr-presentation-functions"]{
-   presented below}).
-
-  @racketblock[
- (∩ (→ Number String) (→ Number Symbol))
- (∩ (→ Number String) (→ Boolean String))]
-
-  The first intersection seems like could be simplified to
-  @racket[(→ Number String) (→ Number Symbol)], and the second one could be
-  simplified to @racket[(→ (U Number Boolean) String)], however the equivalence
-  between these types has not been implemented (yet) in @|typedracket|, so we do
-  not rely on them. Note that this issue is not a soundness issue: it only
-  prevents passing values  types to which they belong in principle, but it
-  cannot be exploited to assign a value to a variable with an incompatible type.
-
-  Finally, when some types are intersected with a polymorphic type variable,
-  the intersection cannot be computed until the polymorphic type is
-  instantiated.
-  
-  When @|typedracket| is able to perform a simplification, occurrences of
-  @racket[Nothing] (the bottom type) propagate outwards in some cases, pairs and
-  struct types which contain @racket[Nothing] as one of their elements being
-  collapsed to @racket[Nothing]. This propagation of @racket[Nothing] starts
-  from occurrences of @racket[Nothing] in the parts of the resulting type which
-  are traversed by the intersection operator. It collapses the containing pairs
-  and struct types to @racket[Nothing], moving outwards until the @racket[∩]
-  operator itself is reached. In principle, the propagation could go on past
-  that point, but this is not implemented yet in @|typedracket|@note{See
-   @hyperlink["https://github.com/racket/typed-racket/issues/552"]{Issue #552}
-   on @|typedracket|'s GitHub repository for more details on what prevents
-   implementing a more aggressive propagation of @racket[Nothing].}.
-
-  The type @racket[(∩ 'a 'b)] therefore gets simplified to @racket[Nothing],
-  and the type @racket[(∩ (Pairof 'a 'x) (Pairof 'b 'x))] also simplifies to
-  @racket[Nothing] (@|typedracket| initially pushes the intersection down the
-  pairs, so that the type first becomes @racket[(Pairof (∩ 'a 'b) (∩ 'x 'x))],
-  which is simplified to @racket[(Pairof Nothing 'x)], and the occurrence of
-  @racket[Nothing] propagates outwards). However, if the user directly specifies
-  the type @racket[(Pairof (∩ 'a 'b) Integer)], it is simplified to
-  @racket[(Pairof Nothing Integer)], but the @racket[Nothing] does not propagate
-  outwards beyond the initial use of @racket[∩].
-
-  @examples[#:label #f #:eval (tr-eval)
-            (:type (∩ 'a 'b))
-            (:type (∩ (Pairof 'a 'x) (Pairof 'b 'x)))
-            (:type (Pairof (∩ 'a 'b) Integer))]
-
-  A simple workaround exists: the outer type, which could be collapsed to
-  @racket[Nothing], can be intersected again with a type of the same shape. The
-  outer intersection will traverse both types (the desired one and the
-  ``shape''), and propagate the leftover @racket[Nothing] further out.
-
-  @examples[#:label #f #:eval (tr-eval)
-            (:type (Pairof (∩ 'a 'b) Integer))
-            (:type (∩ (Pairof (∩ 'a 'b) Integer)
-                      (Pairof Any Any)))]
-
-  These intersections are not very interesting on their own, as in most cases
-  it is possible to express the resulting simplified type without using the
-  intersection operator. They become more useful when mixed with polymorphic
-  types: intersecting a polymorphic type variable with another type can be used
-  to restrict the actual values that may be used. The type @racket[(∩ A T)],
-  where @racket[A] is a polymorphic type variable and @racket[T] is a type
-  defined elsewhere, is equivalent to the use of bounded type parameters in
-  @|java| or @|csharp|. In @|csharp|, for example, the type @racket[(∩ A T)]
-  would be written using an @tt["where A : T"] clause.}
- 
- @asection{
-  @atitle[#:tag "tr-presentation-structs"]{Structs}
-
-  Racket also supports @racket[struct]s, which are mappings from fields to
-  values. A struct is further distinguished by its struct type: instances of two
-  struct types with the same name and fields, declared in separate files, can be
-  differentiated using the predicates associated with these structs. Structs in
-  Racket can be seen as the analog of classes containing only fields (but no
-  methods) in @csharp or @|java|. Such classes are sometimes called ``Plain Old
-  Data (POD) Objects''. Structs belong to a single-inheritance hierarchy:
-  instances of the descendents of a struct type are recognised by their
-  ancestor's predicate. When a struct inherits from another, it includes its
-  parent's fields, and can add extra fields of its own.
-
-  Each struct declaration within a @|typedracket| program additionally declares
-  corresponding type.
-
-  @examples[#:label #f #:eval (tr-eval)
-            (struct parent ([field₁ : (Pairof String Symbol)])
-              #:transparent)
-            (struct s parent ([field₂ : Integer]
-                              [field₃ : Symbol])
-              #:transparent)
-            (s (cons "x" 'y) 123 'z)]
-
-  In @|typedracket|, structs can have polymorphic type arguments, which can be
-  used inside the types of the struct's fields.
-
-  @examples[#:label #f #:eval (tr-eval)
-            (struct (A B) poly-s ([field₁ : (Pairof A B)]
-                                  [field₂ : Integer]
-                                  [field₃ : B])
-              #:transparent)
-            (poly-s (cons "x" 'y) 123 'z)]
-
-  Racket further supports
-  @tech[#:doc '(lib "scribblings/reference/reference.scrbl")]{struct type
-   properties}, which can be seen as a limited form of method definitions for a
-  struct, thereby making them closer to real objects. The same struct type
-  property can be implemented by many structs, and the declaration of a struct
-  type property is therefore roughly equivalent to the declaration of an
-  interface with a single method.
-
-  Struct type properties are often considered a low-level mechanism in Racket.
-  Among other things, a struct type property can only be used to define a single
-  property at a time. When multiple ``methods'' have to be defined at once (for
-  example, when defining the @racket[prop:equal+hash] property, which requires
-  the definition of an equality comparison function, and two hashing functions),
-  these can be grouped together in a list of functions, which is then used as
-  the property's value.
-  ``@seclink["struct-generics"
-             #:doc '(lib "scribblings/reference/reference.scrbl")]{
-   Generic interfaces}'' are a higher-level feature, which among other things
-  allow the definition of multiple ``methods'' as part of a single generic
-  interface, and offers a friendlier API for specifying the ``generic
-  interface'' itself (i.e. what Object Oriented languages call an interfece), as
-  and for specifying the implementation of said interface.
-
-  @|Typedracket| unfortunately offers no support for struct type properties and
-  generic interfaces for now. It is impossible to assert that a struct
-  implements a given property at the type level, and it is also for example not
-  possible to describe the type of a function accepting any struct implementing
-  a given property or generic interface. Finally, no type checks are performed
-  on the body of functions bound to such properties, and to check verifies that
-  a function implementation with the right signature is supplied to a given
-  property. Since struct type properties and generics cannot be used in a
-  type-safe way for now, we refrain from using these features, and only use them
-  to implement some very common properties@note{We built a thin macro wrapper
-   which allows typechecking the implementation and signature of the functions
-   bound to these two properties.}: @racket[prop:custom-write] which is the
-  equivalent of @|java|'s @tt["void toString()"], and @racket[prop:equal+hash]
-  which is equivalent to @|java|'s @tt["boolean equals(Object o)"] and
-  @tt["int hashCode()"].
-
- }
- 
- @asection{
-  @atitle[#:tag "tr-presentation-functions"]{Functions}
-   
-  @|Typedracket| supports rich function types, to support some of the flexible
-  use patterns allowed by Racket.
-
-  The simple function type below indicates that the function expects two
-  arguments (an integer and a string), and returns a boolean:
-
-  @racketblock[(→ Integer String Boolean)]
-
-  We note that unlike @|haskell| and @|CAML| functions, Racket functions are
-  not implicitly curried. To express the corresponding curried function type,
-  one would write:
-
-  @racketblock[(→ Integer (→ String Boolean))]
-
-  A function may additionally accept optional positional arguments, and keyword
-  (i.e. named) arguments, both mandatory and optional:
-
-  @racketblock[
- (code:comment "Mandatory string, optional integer and boolean arguments:")
- (->* (String) (Integer Boolean) Boolean)
- (code:comment "Mandatory keyword arguments:")
- (→ #:size Integer #:str String Boolean)
- (code:comment "Mandatory #:str, optional #:size and #:opt:")
- (->* (#:str String) (#:size Integer #:opt Boolean) Boolean)]
-
-  Furthermore, functions in Racket accept a catch-all ``rest'' argument, which
-  allows for the definition of variadic functions. Typed racket also allows
-  expressing this at the type level, as long as the arguments covered by the
-  ``rest'' clause all have the same type:
-
-  @racketblock[
- (code:comment "The function accepts one integer and any number of strings:")
- (-> Integer String * Boolean)
- (code:comment "Same thing with an optional symbol inbetween: ")
- (->* (Integer) (Symbol) #:rest String Boolean)]
-
-  One of @|typedracket|'s main goals is to be able to typecheck idiomatic
-  Racket programs. Such programs may include functions whose return type depends
-  on the values of the input arguments. Similarly, @racket[case-lambda] can be
-  used to create lambda functions which dispatch to multiple behaviours based on
-  the number of arguments passed to the function.
-
-  @|Typedracket| provides the @racket[case→] type operator, which can be used to
-  describe the type of these functions:
-
-  @racketblock[
- (code:comment "Allows 1 or 3 arguments, with the same return type.")
- (case→ (→ Integer Boolean)
-        (→ Integer String Symbol Boolean))
- (code:comment "A similar type based on optional arguments allows 1, 2 or 3")
- (code:comment " arguments in contrast:")
- (->* (Integer) (String Symbol) Boolean)
- (code:comment "The output type can depend on the input type:")
- (case→ (→ Integer Boolean)
-        (→ String Symbol))
- (code:comment "Both features (arity and dependent output type) can be mixed")
- (case→ (→ Integer Boolean)
-        (→ Integer String (Listof Boolean)))]
-
-  Another important feature, which can be found in the type system of most
-  functional programming languages, and most object-oriented languages, is
-  parametric polymorphism. @|Typedracket| allows the definition of polymorphic
-  structs, as detailed above, as well as polymorphic functions. For example, the
-  function @racket[cons] can be considered as a polymorphic function with two
-  polymorphic type arguments @racket[A] and @racket[B], which takes an argument
-  of type @racket[A], an argument of type @racket[B], and returns a pair of
-  @racket[A] and @racket[B].
-
-  @racketblock[(∀ (A B) (→ A B (Pairof A B)))]
-
-  @htodo{Something on which types can be inferred and which can't (for now).}
-
-  Finally, predicates (functions whose results can be interpreted as booleans)
-  can be used to gain information about the type of their argument, depending on
-  the result. The type of a predicate can include positive and negative filters,
-  indicated with @racket[#:+] and @racket[#:-], respectively. The type of the
-  @racket[string?] predicate is:
-
-  @racketblock[(→ Any Boolean : #:+ String #:- (! String))]
-
-  In this notation, the positive filter @racket[#:+ String] indicates that when
-  the predicate returns @racket[#true], the argument is known to be a
-  @racket[String]. Conversely, when the predicate exits with @racket[#false],
-  the negative filter @racket[#:- (! String)] indicates that the input could not
-  (@racket[!]) possibly have been a string. The information gained this way
-  allows regular conditionals based on arbitrary predicates to work like
-  pattern-matching:
-
-  @examples[#:label #f #:eval (tr-eval)
-            (define (f [x : (U String Number Symbol)])
-              (if (string? x)
-                  (code:comment "x is known to be a String here:")
-                  (ann x String)
-                  (code:comment "x is known to be a Number or a Symbol here:")
-                  (ann x (U Number Symbol))))]
-
-  The propositions do not necessarily need to refer to the value as a whole,
-  and can instead give information about a sub-part of the value. Right now, the
-  user interface for specifying paths can only target the left and right members
-  of @racket[cons] pairs, recursively. Internally, @|typedracket| supports
-  richer paths, and the type inference can produce filters which give
-  information about individual structure fields, or about the result of forced
-  promises, for example.}
-
- @asection{
-  @atitle[#:tag "tr-presentation-recursive-types"]{Recursive types}
-   
-  @|Typedracket| allows recursive types, both via (possibly mutually-recursive)
-  named declarations, and via the @racket[Rec] type operator.
-
-  In the following examples, the types @racket[Foo] and @racket[Bar] are
-  mutually recursive. The type @racket[Foo] matches lists with an even number of
-  alternating @racket[Integer] and @racket[String] elements, starting with an
-  @racket[Integer],
-
-  @racketblock[
- (define-type Foo (Pairof Integer Bar))
- (define-type Bar (Pairof String (U Foo Null)))]
-
-  This same type could alternatively be defined using the @racket[Rec]
-  operator. The notation @racket[(Rec R T)] builds the type @racket[T], where
-  occurrences of @racket[R] are interpreted as recursive occurrences of
-  @racket[T] itself.
-  
-  @racketblock[
- (Rec R
-      (Pairof Integer
-              (Pairof String
-                      (U R Null))))]}
-
- @asection{
-  @atitle{Classes}
-
-  The @racketmodname[racket/class] module provides an object-oriented system for
-  Racket. 
- }
-
- @asection{
-  @atitle{Occurrence typing}
- }
-
- @asection{
-  @atitle{Global type inference}
- }
-}
-\ No newline at end of file
+            http://racket-lang.org/
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+0           0

	www Unnamed repository; edit this file 'description' to name the repository.
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M	.travis.yml	\|	109	+++++++++++++++++++++----------------------------------------------------------
M	scribblings/tr.scrbl	\|	7906	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------