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oscon2015/1_intro.rst
Araq a7de40ae56 fixed typo ':' instead of ','
2015-07-20 19:33:26 +02:00

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============================================================
The ultimate introduction
============================================================
.. raw:: html
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<center><big><big>Slides</big></big></center>
<br />
<center><big><big><big><big>git clone https://github.com/Araq/oscon2015</big></big></big></big></center>
<br />
<br />
<br />
<center><big><big>Download</big></big></center>
<br />
<center><big><big><big><big><a href="http://nim-lang.org/download.html">http://nim-lang.org/download.html</a></big></big></big></big></center>
Installation
============
::
git clone -b devel git://github.com/nim-lang/Nim.git
cd Nim
git clone -b devel --depth 1 git://github.com/nim-lang/csources
cd csources && sh build.sh
cd ..
bin/nim c koch
./koch boot -d:release
What is Nim?
============
- new **systems** programming language
- compiles to C
- garbage collection + manual memory management
- thread local garbage collection
- design goals: efficient, expressive, elegant
..
* Nim compiles to C; C++ and Objective-C are also supported
* there is an experimental JavaScript backend
* it provides a soft realtime GC: you can tell it how long it is allowed to run
* the Nim compiler and **all** of the standard library (including the GC)
are written in Nim
* whole program dead code elimination: stdlib carefully crafted to make use
of it; for instance parsers do not use (runtime) regular expressions ->
re engine not part of the executable
* our infrastructure (IDE, build tools, package manager) is
also completely written in Nim
* infix/indentation based syntax
Philosophy
==========
* power
* efficiency
* fun
..
Talk about what the plans for Nim were
Why Nim?
========
- Major influences: Modula 3, Delphi, Ada, C++, Python, Lisp, Oberon.
- Development started in 2006
- First successful bootstrapping in 2008
- compiler written in Delphi
- converted to Nim via "pas2nim"
Uses of Nim
===========
- games
- compilers
- operating system development
- scientific computing
- scripting
Nim at 3dicc
============
.. raw:: html
<img src="busyteam2.png" />
URLs
====
============ ================================================
Website http://nim-lang.org
Mailing list http://www.freelists.org/list/nim-dev
Forum http://forum.nim-lang.org
Github https://github.com/Araq/Nim
IRC irc.freenode.net/nim
============ ================================================
Hello World
===========
.. code-block:: nim
echo "hello world!"
Hello World
===========
.. code-block:: nim
echo "hello world!"
::
nim c -r hello.nim
More Code!
==========
.. code-block:: nim
:number-lines:
proc decimalToRoman*(number: range[1..3_999]): string =
## Converts a number to a Roman numeral.
const romanComposites = {
"M": 1000, "CM": 900,
"D": 500, "CD": 400, "C": 100,
"XC": 90, "L": 50, "XL": 40, "X": 10, "IX": 9,
"V": 5, "IV": 4, "I": 1}
result = ""
var decVal = number.int
for key, val in items(romanComposites):
while decVal >= val:
decVal -= val
result.add(key)
echo decimalToRoman(1009) # MIX
- ``{"M": 1000, "CM": 900}`` sugar for ``[("M", 1000), ("CM", 900)]``
- ``result`` implicitly available
Nimble
======
- Live demo.
Function application
====================
Function application is ``f()``, ``f(a)``, ``f(a, b)``.
Function application
====================
Function application is ``f()``, ``f(a)``, ``f(a, b)``.
And here is the sugar:
=========== ================== ===============================
Sugar Meaning Example
=========== ================== ===============================
``f a`` ``f(a)`` ``spawn log("some message")``
``a.f()`` ``f(a)`` ``db.fetchRow()``
``a.f`` ``f(a)`` ``mystring.len``
``f a, b`` ``f(a, b)`` ``echo "hello ", "world"``
``a.f(b)`` ``f(a, b)`` ``myarray.map(f)``
``a.f b`` ``f(a, b)`` ``db.fetchRow 1``
``f"\n"`` ``f(r"\n")`` ``re"\b[a-z*]\b"``
=========== ================== ===============================
Function application
====================
Function application is ``f()``, ``f(a)``, ``f(a, b)``.
And here is the sugar:
=========== ================== ===============================
Sugar Meaning Example
=========== ================== ===============================
``f a`` ``f(a)`` ``spawn log("some message")``
``a.f()`` ``f(a)`` ``db.fetchRow()``
``a.f`` ``f(a)`` ``mystring.len``
``f a, b`` ``f(a, b)`` ``echo "hello ", "world"``
``a.f(b)`` ``f(a, b)`` ``myarray.map(f)``
``a.f b`` ``f(a, b)`` ``db.fetchRow 1``
``f"\n"`` ``f(r"\n")`` ``re"\b[a-z*]\b"``
=========== ================== ===============================
**BUT**: ``f`` does not mean ``f()``; ``myarray.map(f)`` passes ``f`` to ``map``
Operators
=========
* operators are simply sugar for functions
* operator in backticks is treated like an identifier
::
`@`(x, y)
x.`@`(y)
`@`(x)
x.`@`()
x.`@`
Operators
=========
* Of course, most of the time binary operators are simply invoked as ``x @ y``
and unary operators as ``@x``.
* No explicit distinction between binary and unary operators:
.. code-block:: Nim
:number-lines:
proc `++`(x: var int; y: int = 1; z: int = 0) =
x = x + y + z
var g = 70
++g
g ++ 7
g.`++`(10, 20)
echo g # writes 108
* parameters are readonly unless declared as ``var``
* ``var`` means "pass by reference" (implemented with a hidden pointer)
Control flow
============
- The usual control flow statements are available:
* if
* case
* when
* while
* for
* try
* defer
* return
* yield
If vs when
==========
.. code-block:: nim
:number-lines:
when defined(posix):
proc getCreationTime(file: string): Time =
var res: Stat
if stat(file, res) < 0'i32:
let error = osLastError()
raiseOSError(error)
return res.st_ctime
Statements vs expressions
=========================
Statements require indentation:
.. code-block:: nim
# no indentation needed for single assignment statement:
if x: x = false
# indentation needed for nested if statement:
if x:
if y:
y = false
else:
y = true
# indentation needed, because two statements follow the condition:
if x:
x = false
y = false
Statements vs expressions
=========================
Expressions do not:
.. code-block:: nim
if thisIsaLongCondition() and
thisIsAnotherLongCondition(1,
2, 3, 4):
x = true
- Rule of thumb: optional indentation after operators, ``(`` and ``,``
- ``if``, ``case`` etc also available as expressions
Builtin types
=============
- ``int`` -- platform dependent (16) 32 or 64 bit signed number
* overflows produce an exception in debug mode; wrap around in release mode
- ``float`` -- 64 bit floating point number
* float64 an alias for float
* float32 32 bit floating point number
- ``int8`` / ``int16`` / ``int32`` / ``int64``
* integer types with a platform independent size
Builtin types
=============
- ``uint`` / ``uint8`` / ``uint16`` / ``uint32`` / ``uint64``
* like in C, always wrap around; modulo arithmetic
* heavily discouraged: ``for in 0 .. x.len - 3``
should iterate 0 times when ``x.len == 0``, not 4294967293 times!
* instead: use ``Natural``
- ``range[T]``
* subrange type; quite heavily used in Nim
(``type Natural = range[0..high(int)]``)
- ``bool``
Builtin types
=============
- ``array[FixedSize, T]``
* fixed size in Nim
* value based datatypes
* layout is compatible to C
* create via ``[1, 2, 3]`` construction
- ``seq[T]``
* dynamically resizable at runtime
* grow with ``add``, resize with ``setLen``
* create via ``@`` or ``newSeq``: ``@[1, 2, 3]``
* allocated on the heap and GC'ed
- ``openArray[T]``
* allows to pass ``seq`` or ``array`` to a routine
* internally a (pointer, length) pair
Builtin types
=============
- ``proc (a, b: string) {.closure.}``
* functions are first class in Nim
* "calling convention" affects type compatibility
* ``closure`` is a special calling convention (closures are GC'ed)
- ``char`` / ``string`` / ``cstring``
* ``char`` is simply an octet, ``string`` is almost a ``seq[char]``.
* ``string`` is (usually) allocated on the heap and GC'ed
Builtin types
=============
``tuple``
* value based datatypes
* structural typing
* optional field names
* construct with ``()``
.. code-block:: Nim
:number-lines:
proc `+-`(x, y: int): (int, int) = (x - y, x + y)
# alternatively
proc `+-`(x, y: int): tuple[lowerBound, upperBound: int] = (x - y, x + y)
let tup = 100 +- 10
echo tup[0], " ", tup.upperBound
# tuple unpacking
let (lower, _) = 100 +- 10
Builtin types
=============
``object``
* value based datatypes
.. code-block:: nim
:number-lines:
type
Rect = object
x, y, w, h: int
# construction:
let r = Rect(x: 12, y: 22, w: 40, h: 80)
# field access:
echo r.x, " ", r.y
Builtin types
=============
enums & sets
.. code-block:: nim
:number-lines:
type
SandboxFlag* = enum ## what the interpreter should allow
allowCast, ## allow unsafe language feature: 'cast'
allowFFI, ## allow the FFI
allowInfiniteLoops ## allow endless loops
SandboxFlags* = set[SandboxFlag]
proc runNimCode(code: string; flags: SandboxFlags = {allowCast, allowFFI}) =
...
Builtin types
=============
.. code-block:: C
:number-lines:
#define allowCast (1 << 0)
#define allowFFI (1 << 1)
#define allowInfiniteLoops (1 << 1)
void runNimCode(char* code, unsigned int flags = allowCast|allowFFI);
runNimCode("4+5", 700);
Builtin types
=============
``ref`` and ``ptr``
* pointers; ``ref`` is a "traced" pointer, ``ptr`` is an "untraced" pointer
* ``string``, ``seq``, ``ref`` and ``closure`` are GC'ed, nothing else
* ``ref object`` an idiom to get reference semantics out of objects
Regular expressions
===================
.. code-block:: nim
:number-lines:
# Model a regular expression
type
RegexKind = enum ## the regex AST's kind
reChar, ## character node "c"
reCClass, ## character class node "[a-z]"
reStar, ## star node "r*"
rePlus, ## plus node "r+"
reOpt, ## option node "r?"
reCat, ## concatenation node "ab"
reAlt, ## alternatives node "a|b"
reWordBoundary ## "\b"
RegExpr = ref object
case kind: RegexKind
of reWordBoundary: discard
of reChar:
c: char
of reCClass:
cc: set[char]
of reStar, rePlus, reOpt:
child0: RegExpr
of reCat, reAlt:
child1, child2: RegExpr
Equality
========
.. code-block:: nim
:number-lines:
proc `==`(a, b: RegExpr): bool =
if a.kind == b.kind:
case a.kind
of reWordBoundary: result = true
of reChar: result = a.c == b.c
of reCClass: result = a.cc == b.cc
of reStar, rePlus, reOpt: result = `==`(a.child0, b.child0)
of reCat, reAlt: result = `==`(a.child1, b.child1) and
`==`(a.child2, b.child2)
Accessors
=========
.. code-block:: nim
:number-lines:
type
HashTable[K, V] = object
data: seq[(K, V)]
proc hash[K](k: K): int = 0
proc `[]`*[K, V](x: HashTable[K, V]; k: K): V =
result = x.data[hash(k)][1]
proc `[]=`*[K, V](x: var HashTable[K, V]; k: K, v: V) =
x.data[hash(k)][1] = v
proc initHashTable[K, V](): HashTable[K, V] =
result.data = @[]
var tab = initHashTable[string, string]()
tab["key"] = "abc" # calls '[]=' accessor
echo tab["key"] # calls '[]' accessor
Accessors
=========
.. code-block:: nim
:number-lines:
type
HashTable[K, V] = object
data: seq[(K, V)]
proc hash[K](k: K): int = 0
proc `[]`*[K, V](x: HashTable[K, V]; k: K): V =
result = x.data[hash(k)][1]
proc `[]=`*[K, V](x: var HashTable[K, V]; k: K, v: V) =
x.data[hash(k)][1] = v
proc initHashTable[K, V](): HashTable[K, V] =
result.data = @[]
var tab = initHashTable[string, string]()
tab["key"] = "abc" # calls '[]=' accessor
echo tab["key"] # calls '[]' accessor
# ouch:
tab["key"].add "xyz"
Accessors
=========
.. code-block:: nim
:number-lines:
proc `[]`*[Key, Value](x: var HashTable[Key, Value]; k: Key): var Value =
result = x.data[hash(key)]
var
tab = initHashTable[string, string]()
# compiles :-)
tab["key"].add "xyz"
* ``var`` "pass by reference" for parameters
* can also by used for return values
Distinct
========
.. code-block:: nim
:number-lines:
# Taken from system.nim
const taintMode = compileOption("taintmode")
when taintMode:
type TaintedString* = distinct string
proc len*(s: TaintedString): int {.borrow.}
else:
type TaintedString* = string
proc readLine*(f: File): TaintedString {.tags: [ReadIOEffect], benign.}
Distinct
========
.. code-block:: nim
:number-lines:
# taintmode_ex
echo readLine(stdin)
::
nim c -r --taintMode:on taintmode_ex
Distinct
========
.. code-block:: nim
:number-lines:
# taintmode_ex
echo readLine(stdin).string
::
nim c -r --taintMode:on taintmode_ex
Distinct
========
.. code-block:: nim
:number-lines:
# taintmode_ex
proc `$`(x: TaintedString): string {.borrow.} # but: defeats the purpose
echo readLine(stdin)
::
nim c -r --taintMode:on taintmode_ex
Module system
=============
.. code-block::nim
:number-lines:
# Module A
var
global*: string = "A.global"
proc p*(x: string) = echo "exported ", x
.. code-block::nim
:number-lines:
# Module B
import A
echo p(global)
Module system
=============
.. code-block::nim
:number-lines:
# Module A
var
global*: string = "A.global"
proc p*(x: string) = echo "exported ", x
.. code-block::nim
:number-lines:
# Module B
from A import p
echo p(A.global)
Module system
=============
.. code-block::nim
:number-lines:
# Module A
var
global*: string = "A.global"
proc p*(x: string) = echo "exported ", x
.. code-block::nim
:number-lines:
# Module B
import A except global
echo p(A.global)
Routines
========
- ``proc``
- ``iterator``
- ``template``
- ``macro``
- ``method``
- ``converter``
- (``func``)
Iterators
=========
.. code-block:: nim
:number-lines:
iterator `..<`(a, b: int): int =
var i = a
while i < b:
yield i
i += 1
for i in 0..<10:
echo i+1, "-th iteration"
Iterators
=========
.. code-block:: nim
:number-lines:
for x in [1, 2, 3]:
echo x
Iterators
=========
.. code-block:: nim
:number-lines:
for x in [1, 2, 3]:
echo x
Rewritten to:
.. code-block:: nim
:number-lines:
for x in items([1, 2, 3]):
echo x
..
for i, x in foobar is rewritten to use the pairs iterator
Iterators
=========
.. code-block:: nim
:number-lines:
iterator items*[IX, T](a: array[IX, T]): T {.inline.} =
var i = low(IX)
while i <= high(IX):
yield a[i]
i += 1
Iterators
=========
.. code-block:: nim
:number-lines:
for x in [1, 2, 3]:
x = 0 # doesn't compile
Iterators
=========
.. code-block:: nim
:number-lines:
var a = [1, 2, 3]
for x in a:
x = 0 # doesn't compile
Iterators
=========
.. code-block:: nim
:number-lines:
iterator mitems*[IX, T](a: var array[IX, T]): var T {.inline.} =
var i = low(IX)
if i <= high(IX):
while true:
yield a[i]
if i >= high(IX): break
i += 1
var a = [1, 2, 3]
for x in mitems(a):
x = 0 # compiles
Parallelism
===========
.. code-block::nim
:number-lines:
import tables, strutils
proc countWords(filename: string): CountTableRef[string] =
## Counts all the words in the file.
result = newCountTable[string]()
for word in readFile(filename).split:
result.inc word
Parallelism
===========
.. code-block::nim
:number-lines:
#
#
const
files = ["data1.txt", "data2.txt", "data3.txt", "data4.txt"]
proc main() =
var tab = newCountTable[string]()
for f in files:
let tab2 = countWords(f)
tab.merge(tab2)
tab.sort()
echo tab.largest
main()
Parallelism
===========
.. code-block::nim
:number-lines:
import threadpool
const
files = ["data1.txt", "data2.txt", "data3.txt", "data4.txt"]
proc main() =
var tab = newCountTable[string]()
var results: array[files.len, ***FlowVar[CountTableRef[string]]***]
for i, f in files:
results[i] = ***spawn*** countWords(f)
for i in 0..high(results):
tab.merge(*** ^results[i] ***)
tab.sort()
echo tab.largest
main()
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