What is a string?

Strings can be created with quotation marks



In [77]:

    
str="hello world 😀"









    Out[77]:





"hello world 😀"

We can access characters of a string with brackets:



In [84]:

    
str[1],str[13]









    Out[84]:





('h','😀')

Spaces are also characters



In [80]:

    
str[6]









    Out[80]:





' '

Each character is a bit type, in this case using 32 bits/8 bytes:



In [82]:

    
typeof(str[6]), length(bits(str[6]))









    Out[82]:





(Char,32)

Strings are not bit types, but rather point to the start of sequence of Char in memory. In this case, there are $32*13=416$ bits/52 bytes in memory

What is a Vector?

We can create a vector using brackets:



In [83]:

    
v=[11,24,32]









    Out[83]:





3-element Array{Int64,1}:
 11
 24
 32

Like a string, elements are accessed via brackets:



In [85]:

    
v[1],v[3]









    Out[85]:





(11,32)

Accessing outside the range gives an error



In [86]:

    
v[4]









    



LoadError: BoundsError: attempt to access 3-element Array{Int64,1}:
 11
 24
 32
  at index [4]
while loading In[86], in expression starting on line 1

 in getindex at array.jl:282

Vectors can be made with different types, for example, here is a vector of 3 8-bit integers:



In [87]:

    
v=[Int8(11),Int8(24),Int8(32)]









    Out[87]:





3-element Array{Int8,1}:
 11
 24
 32

Just like strings, Vectors are not bit types, but rather point to the start of sequence of the corresponding type. In this last case, there are $3*8=24$ bits/3 bytes in memory

Parsing strings

We can use the command parse to turn a string into an integer



In [88]:

    
parse(Int,"123")









    Out[88]:





123

We can specify base 2 by adding a 2 at the end:



In [90]:

    
bts="00000000000000011111011001001010"
x=parse(Int32,bts,2)









    Out[90]:





128586

reinterpret allows us to reinterpret the resulting sequence of 32 bits as a different type, for example, a Char



In [91]:

    
reinterpret(Char,x)









    Out[91]:





'🙊'