Julia 연습 12

In [ ]:

#
# 나는 julia 를 사랑하는가
#

In [ ]:

# 새로운 객체를 만들어내는 함수를 생성자라고 부른다.
# Constructors

In [1]:

type Foo
    bar
    baz
end

In [2]:

foo = Foo( 1, 2)

Out[2]:

Foo(1,2)

In [3]:

foo.bar

Out[3]:

1

In [4]:

foo.baz

Out[4]:

2

In [5]:

# Outer Constructor

Foo(x) = Foo(x, x)

Out[5]:

Foo

In [6]:

foo = Foo(5)

Out[6]:

Foo(5,5)

In [7]:

Foo() = Foo(0)

Out[7]:

Foo

In [8]:

foo = Foo()

Out[8]:

Foo(0,0)

In [9]:

# Outer constructor
# Inner constructor
# 외부 생성자
# 내부 생성자

type OrderedPair
    x::Real
    y::Real
    
    OrderedPair(x, y) = x > y ? error("순서가 틀려먹었다") : new(x,y)
end

In [10]:

OrderedPair(1,2)

Out[10]:

OrderedPair(1,2)

In [11]:

OrderedPair(2,1)

LoadError: 순서가 틀려먹었다
while loading In[11], in expression starting on line 1

 in call at In[9]:10

In [12]:

# 불완전 초기화
# 자기참조 객체
# 재귀적 데이타 구조


type SelfReferential
    obj::SelfReferenctial
end

LoadError: UndefVarError: SelfReferenctial not defined
while loading In[12], in expression starting on line 3

In [14]:

type SelfReferential
    obj::SelfReferential
    
    SelfReferential() = (x = new(); x.obj = x)
end

In [15]:

x = SelfReferential()

Out[15]:

SelfReferential(SelfReferential(#= circular reference =#))

In [16]:

is(x, x)

Out[16]:

true

In [17]:

is(x, x.obj)

Out[17]:

true

In [18]:

is(x, x.obj.obj)

Out[18]:

true

In [19]:

type Incomplete
    xx
    Incomplete() = new()
end

In [20]:

z = Incomplete()

Out[20]:

Incomplete(#undef)

In [21]:

z.xx

LoadError: UndefRefError: access to undefined reference
while loading In[21], in expression starting on line 1

In [22]:

type HasPlain
    n::Int
    HasPlain() = new()
end

In [23]:

h = HasPlain()

Out[23]:

HasPlain(140045355964904)

In [24]:

h.n

Out[24]:

140045355964904

In [25]:

# Parametric Constructor


type Point{T <: Real}
    x::T
    y::T
end

In [26]:

Point(1,2)

Out[26]:

Point{Int64}(1,2)

In [27]:

Point(1.0, 2.5)

Out[27]:

Point{Float64}(1.0,2.5)

In [28]:

Point(1, 2.5)

LoadError: MethodError: `convert` has no method matching convert(::Type{Point{T<:Real}}, ::Int64, ::Float64)
This may have arisen from a call to the constructor Point{T<:Real}(...),
since type constructors fall back to convert methods.
Closest candidates are:
  Point{T<:Real}(::T<:Real, !Matched::T<:Real)
  call{T}(::Type{T}, ::Any)
  convert{T}(::Type{T}, !Matched::T)
while loading In[28], in expression starting on line 1

 in call at essentials.jl:57

In [29]:

Point{Int64}(1.0, 2.5)

LoadError: InexactError()
while loading In[29], in expression starting on line 1

 in call at In[25]:2

In [30]:

Point{Float64}(1.0,2.5)

Out[30]:

Point{Float64}(1.0,2.5)

In [31]:

Point{Float64}(1,2)

Out[31]:

Point{Float64}(1.0,2.0)

In [32]:

x = 1

Out[32]:

1

In [33]:

typeof(x)

Out[33]:

Int64

In [34]:

y = convert(Float64, x)

Out[34]:

1.0

In [35]:

typeof(y)

Out[35]:

Float64

In [36]:

x2, y2 = promote( x, y)

Out[36]:

(1.0,1.0)

In [37]:

( typeof(x2), typeof(y2))

Out[37]:

(Float64,Float64)

In [38]:

typeof(ans)

Out[38]:

Tuple{DataType,DataType}

In [39]:

s = widen(Int32)

Out[39]:

Int64

In [40]:

typeof(s)

Out[40]:

DataType