LB Booster
Programming >> Liberty BASIC language >> array operations
http://lbb.conforums.com/index.cgi?board=lblang&action=display&num=1434988071
array operations
Post by Alincon on Jun 22nd, 2015, 3:47pm

I have a program that consists of several listboxes that, together, work like a spreadsheet. It does row and column totals and averages, etc.
What I want to do is allow the user to enter something like
A + B = C or C = A + B The program would then add the contents of each element in column A (listbox A) to the corresponding element in column B (listbox B) and place the results in the corresponding elements in column C (listbox C)
(I'd like to do subtraction, multiplication and division, too)
I was trying to use Eval statements in LB, but was unsuccessful.
How can I use the array operation statements to do what I want in LBB?

r.m.
Re: array operations
Post by tsh73 on Jun 22nd, 2015, 5:35pm

Code:
dim a(5), b(5), c(5)

for i = 1 to 5
    a(i)=i
    b(i)=10*i
next

c()=a()+b()
gosub [printArr]

c()=b()-a()
gosub [printArr]

c()=a()*b()
gosub [printArr]

a(0)=1  'or we have division by zero - obviously array operations start with 0's item
c()=b()/a()
gosub [printArr]

end

[printArr]
for i = 1 to 5
    print c(i);" ";
next
print
return


Als, for LBB specific EVAL things, see reply#5 of the
The future of LBB - please read thread.
Re: array operations
Post by Alincon on Jun 26th, 2015, 8:08pm

Okay, I see how to do math on arrays, but I guess I didn't make it clear that translating user input is a different problem.
I don't want to do this:
Code:
If userInput$ = "A+B=C" then C()=A()+B()
If userInput$ = "C=A+B" then C()=A()+B()
If userInput$ = "A*B=C" then C()=A()*B()
If userInput$ = "C=A*B" then C()=A()*B()
If userInput$ = "D+E=F" then D()=E()+F()
If userInput$ = "J=I/H" then J()=I()/H()
...


Can I use the EVAL statement to translate user input?

r.m.
Re: array operations
Post by Richard Russell on Jun 27th, 2015, 06:37am

on Jun 26th, 2015, 8:08pm, Alincon wrote:
Can I use the EVAL statement to translate user input?

EVAL can only return a single numeric or string value, not an entire array, so you would have to evaluate each element individually in a loop. That would involve some fairly straightforward string manipulation to convert "A+B" into "A(i)+B(i)" for example.

Once you've evaluated each element you then have to assign those values to the output array (e.g. "C(i)"). You could use the FNassign kludge in the linked thread to do that.

So possible, but quite messy:

Code:
    dim A(10), B(10), C(10)
    userInput$ = "C=A*B"
    lhs$ = AddIndices$(word$(userInput$, 1, "="))
    rhs$ = AddIndices$(word$(userInput$, 2, "="))
    for i = 0 to 10
      dummy = eval("FNassign("+lhs$+","+rhs$+")")
    next
    end

function AddIndices$(a$)
    i = 1
    while i <= len(a$)
      if instr(" +-*/", mid$(a$,i,1)) then
        i += 1
      else
        a$ = left$(a$,i) + "(i)" + mid$(a$,i+1)
        i += 4
      end if
    wend
    AddIndices$ = a$
end function

function assign(byref a, b)
    a = b
end function

Richard.

Re: array operations
Post by Richard Russell on Jun 28th, 2015, 09:51am

Here's a more functional example:

Code:
    WindowWidth = 640
    WindowHeight = 300
    dim A(9),B(9),C(9),D(9),E(9),F(9),G(9),H(9),I(9)
    nomainwin

    for row = 0 to 5
      x = 10
      for col = 0 to 9
        if col = 0 then
          stylebits #w.tb _ES_CENTER, 0, 0, 0
          w = 120
        else
          stylebits #w.tb _ES_READONLY, 0, 0, 0
          w = 47
        end if
        textbox #w.tb, x, row*30+20, w, 20
        x += w + 7
        maphandle #w.tb, "#w.tb";row;col
      next col
    next row
    stylebits #w.tb00 _ES_READONLY or _ES_CENTER, 0, 0, 0
    button #w, "RECALCULATE", [recalc], UL, 260, 210
    open "Array calculations" for window as #w
    #w "trapclose [quit]"
    #w.tb00 "index (i)"
    #w.tb10 "A = i + 2"
    #w.tb20 "B = SQR(A)"
    #w.tb30 "C = A - B"
    #w.tb40 "D = B * C"
    #w.tb50 "E = D / A"
    for col = 1 to 9
      handle$ = "#w.tb0";col
      #handle$ "!disable"
      #handle$ col
    next col
    #w.tb10 "!setfocus"
[recalc]
    for row = 1 to 5
      handle$ = "#w.tb";row;0
      #handle$ "!contents? userInput$"
      if userInput$ <> "" then
        lhs$ = AddIndices$(word$(userInput$, 1, "="))
        rhs$ = AddIndices$(word$(userInput$, 2, "="))
        for i = 1 to 9
          handle$ = "#w.tb";row;i
          try 
            dummy = eval("FNassign("+lhs$+","+rhs$+")")
            #handle$ eval(lhs$)
          catch
            #handle$ Err$
          end try
        next i
      end if 
    next row
    wait

[quit]
    close #w
    end

function AddIndices$(a$)
    i = 1
    while i <= len(a$)
      if (i = 1 or not(IsCap(mid$(a$, i-1, 1)))) and _
          IsCap(mid$(a$, i, 1)) and _
          not(IsCap(mid$(a$, i+1, 1))) then 
        a$ = left$(a$,i) + "(i)" + mid$(a$,i+1)
        i += 3
      end if
      i += 1
    wend
    AddIndices$ = a$
end function

function IsCap(a$)
    IsCap = (a$ >= "A" and a$ <= "Z")
end function

function assign(byref a, b)
    a = b
end function

Richard.
Re: array operations
Post by Alincon on Jun 30th, 2015, 2:39pm

Thank you for taking the time to code this example.
I will need some time to understand it, and try to apply it to my program.

r.m.

(in LB, the program aborts on the stylebits statements)
Re: array operations
Post by Richard Russell on Jun 30th, 2015, 3:05pm

on Jun 30th, 2015, 2:39pm, Alincon wrote:
in LB, the program aborts on the stylebits statements

Yes I know: I put a space where there should be a comma. But since the program cannot run in LB anyway, it doesn't really matter.

Richard.