Tuesday 4/16/02 Chapter 10

Student Notes

 

Objectives

Strings

Files

 

1. The String Data Type

  • We have all ready worked with Strings for most of the semester
  • a string is an
  • it is possible to assign or refer to a
  • Strings can be assigned to each other, but their
  • Strings can be                                                   to form longer strings

 

 

 

 

2. String vs. Character

  • it is possible to have a String on only one character, however “A” /= ‘A’

 

 

 

 

 

3. Dealing with strings of variable length

  • Ada.Text_IO.Get_Line allows us to count the number of continuous, non-white space characters in an input stream
  • NameLength : Natural;
  • Ada.Text_IO.Get_Line(Item => LastName, Last => NameLength);
  • LastName must be a string of a predefined length, and if the input string is shorter than LastName, the characters after position NameLength are
  •  
  •  

 

 

 

 

 

4. String Slicing

·   FirstName(1..4)

·   LastName(5..11)

·   These are slices of the strings FirstName and LastName. the first through fourth characters of FirstName and the fifth through eleventh characters of LastName

·   Ada.Text_IO.Put(Item=>LastName(1..NameLength);

·   This uses the number of defined characters for output. This is very nice for formatting text

 

5. String Mapping packages

  • Ada provides some packages for automatically mapping on character into another
  • page 441

 

 

6. Text files

  • Text files may used for reading or writing but
  •  
  •  
  • The size of the text file is not limited.
  • The end of a file is designated by  a special
  •  
  • this is called a
  •  
  • Then end of a line is specified by a
  •  
  •  
  • This is a text file. <eol>
  • It has two lines. <eol><eof>
  •  
  •  
  • The key board can be viewed as file input as well
  • We can detect an <eol> or <eof> by using the End_Of_Line or End_Of_File functions in Ada
  • LOOP

    EXIT WHEN Ada.Text_IO.End_Of_Line(data file)

    some program statements

  END LOOP

 

7. Getting Input values from a String

  • We can read data in from a string as well as from a file or from Standard Input (the key board)
  • If we have a string of tokens as we expect he first token to be an integer, we can get that integer from the string
  • page 459

 

8. Command Line Parameters

  • Often times we would like the user to be able to start the program and give us some initial values (ex. sortfile.exe myfile.dat)
  • Ada provides a packages for handling command line data Ada.Command_Line
  • page 460