Strings

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• Misc
  • Solution to exam 2 now online via “Exercises” page
  • SOFIs
    • Helpful to me in teaching this (or other) courses in future
    • Access through myGeneseo/KnightWeb
  • Final
    • Dec. 22 (Tuesday), noon
    • Comprehensive, but emphasizing material since 2nd hour exam (e.g., cell arrays, strings, files)
    • Rules and format similar to hour exams, especially open references
    • Except designed for 2 hours, you have 3
    • Donuts and cider
• Questions?
• Strings
  • Summary of sections 8.1 through 8.4 in book
    • Strings are row arrays of characters
    • Characters have integer codes
      • Different codes for upper and lower case - upper case letter not equal to lower case equivalent
    • Whitespace characters
    • Many tables of functions to operate on strings
      • Pick out letters
      • Concatenate
      • Comparison
      • etc.
  • Examples / demonstration
    

    >> % Hello world
    >> hello = 'Hello world'
    hello =
    Hello world
    >> % Can do vector things to strings -- e.g., transpose, index, etc.
    >> hello'
    ans =
    H
    e
    l
    l
    o
     
    w
    o
    r
    l
    d
    >> hello(7)
    ans =
    w
    >> hello(2:5)
    ans =
    ello
    >> length(hello)
    ans =
        11
    >> % Upper vs lower case matters: various ways of comparing strings handle this differently
    >> s = 'Hello World'
    s =
    Hello World
    >> hello == s
    ans =
      Columns 1 through 9
         1     1     1     1     1     1     0     1     1
      Columns 10 through 11
         1     1
    >> strcmp( hello, s )
    ans =
         0
    >> hello
    hello =
    Hello world
    >> s
    s =
    Hello World
    >> strcmpi( hello, s )
    ans =
         1
    >> helloBackward = hello( end:-1:1 )
    helloBackward =
    dlrow olleH
    >> strcmp( hello, helloBackward )
    ans =
         0
    >> if hello == s
    fprintf( 'Equal!\n' )
    else
    fprintf( 'Not Equal!\n' )
    end
    Not Equal!
    >> if hello == hello
    fprintf( 'Equal!\n' )
    else
    fprintf( 'Not Equal!\n' )
    end
    Equal!
    >> strcmp( hello, s )
    ans =
         0
    >> strncmp( hello, s, 5 )
    ans =
         1
    >> hello == 'hello'
    Error using ==
    Matrix dimensions must agree. 
    >> strcmp( hello, 'hello' )
    ans =
         0
    >> strcmp( hello, 0 )
    ans =
         0
    >> isequal( hello, 'hello' )
    ans =
         0
    >> isequal( hello, 0 )
    ans =
         0
    >> isequal( 0, 0 )
    ans =
         1
    >> % Character codes really occupy (at least) 16 bits and use Unicode rather than ASCII
    >> char( 65 )
    ans =
    A
    >> uint8( 'A' )
    ans =
       65
    >> char( 8706 )
    ans =
    ∂
    >> uint8( '∂' )
    ans =
      255
    >> uint16( '∂' )
    ans =
       8706
    >> % isequal function handles arbitrary size mismatches in vectors
    >> isequal( hello, 'hello' )
    ans =
         0
    >> isequal( [1 2 3], linspace(1,10,1000) )
    ans =
         0

• Relations Lab
  • Double-clicking on a cell array in the Workspace pane opens a cell array editor
• Next
  • Files
  • Read section 6.5 in textbook

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