Eiffel Help for Beginner? Please?

by Jasmine Jernigan (modified: 2007 Apr 20)

I am currently working on a small program for school for standard input/output. I am having trouble with read_word (or read_line) and then last_string. Sometimes it uses the most current last_string instead of the one to which it was assigned. Can anyone please help me with this? Thanks --Great_Jasmini (not-so-great-at-eiffel-programming)

PS. I think the root of my problem is linked with another little sample problem that I dont understand. Why is it that if you do: local my_array:ARRAY[STRING] do create my_array(1,2) from i:=1 until i=10 loop 

 io.read_word
 my_array.force(last_string, i)
 i:=i+1

end

end

when i run code similar to this and then type in different words for the array, when i print off the array it is all the last word. Any help? Please? Thanks in advance--Jasmine

Comments
  • Colin Adams (17 years ago 20/4/2007)

    Typo?

    Hello Jasmine,

    Firstly, it would be easier to read your code if you included it within eiffel XML tags (see MediaWiki syntax when posting).

    I can see a few problems with your code.

    Firstly, it should be io.last_string (you omitted the io.). Secondly, I think you need to call io.last_string.twin, which will copy the last string. The problem is that io.last_string is re-used, so all the entries in your array point to the same object.

    Thirdly, since you know the size of the array, it would be better to size it correctly, and use put, not force.

    Also, avoid loops when you can (not always possible). Agents are better.

    So something like this:

    feature -- Test test is -- Test reading multiple words from standard input local my_array: ARRAY [STRING] i: INTEGER do create my_array.make (1, 10) from i := 1 until i > 10 loop io.read_word my_array.put (io.last_string.twin, i) i := i + 1 end my_array.do_all (agent print_line) end print_line (a_string: STRING) is -- Print `a_string' on standard output followed by a new line. require a_string_not_void: a_string /= Void do print (a_string + "%N") end Colin Adams