PI : many digits try

[bluatigro]

error :

i got zero digits

code was translated from vb2005

[/p][p]global n : n = 100
notice find.pi$()
end
function string$( char$ , t )
 uit$ = ""
 for i = 1 to t
   uit$ = uit$ + char$
 next i
end function
function multiply$( a$ , f )
 c = 0
 uit$ = ""
 for p = n to 1 step -1
   h = val( mid$( a$ , p , 1 ) ) * f + c
   c = int( h / 10 )
   uit$ = str$( h mod 10 ) + uit$
 next p
 multiply$ = ui$
end function
function divide$( a$ , f )
 b = 0
 uit$ = ""
 for p = n to 1 step -1
   h = val( mid$( a$ , p , 1 ) ) + b * 10
   uit$ = str$( int( h / f ) ) + uit$
   b = h mod f
 next p
 divide$ = uit$
end function
function add$( a$ , b$ )
 c = 0
 uit$ = ""
 for p = n to 0 step -1
   a = val( mid$( a$ , p , 1 ) )
   b = val( mid$( b$ , p , 1 ) )
   h = a + b + c
   c = int( h / 10 )
   uit$ = str$( h mod 10 ) + uit$
 next p
 add$ = uit$
end function
function subtract$( a$ , b$ )
 b = 0
 uit$ = ""
 for p = n to 0 step -1
   a = val( mid$( a$ , p , 1 ) )
   b = val( mid$( b$ , p , 1 ) )
   h = a - b + 10
   b = int( h / 10 )
   uit$ = str$( h mod 10 ) + uit$
 next p
 subtract$ = uit$
end function
function is.zero( a$ )
 uit = 1
 for p = 0 to n
   if val( mid$( a$ , p , 1 ) ) then uit = 0
 next p
 is.zero = uit
end function
sub arctan byref t$ , byref s$ , div
'' arctan( x ) = x - x ^ 3 / 3 + x ^ 5 / 5 ....
 s$ = "1" + right$( s$ , len( s$ ) - 1 )
 i = 1
 w = div
 s$ = divide$( s$ , w )
 t$ = add$( t$ , s$ )
 do
   s$ = multiply$( s$ , i )
   w = div * div
   s$ = divide$( s$ , w )
   i = i + 2
   w = i
   s$ = divide$( s$ , w )
   t$ = subtract$( t$ , s$ )
   s$ = multiply$( s$ , i )
   w = div * div
   s$ = divide$( s$ , w )
   i = i + 2
   w = i
   s$ = divide$( s$ , w )
   t$ = add$( t$ , s$ )
 loop until is.zero( s$ )
end sub
function find.pi$()
'' pi / 4 = atan( 1 / 2 ) + atan( 1 / 3 )
 uit$ = "pi = 3."
 t$ = string$( "0" , n + 2 )
 s$ = string$( "0" , n + 2 )
 f = 2
 call arctan t$ , s$ , f
 f = 3
 call arctan t$ , s$ , f
 find.pi$ = uit$ + multiply$( t$ , 4 )
end function
[/p][p]

[tsh73]

I spot typoos in (fixed)
function string$( char$ , t )
 uit$ = ""
 for i = 1 to t
   uit$ = uit$ + char$
 next i
 string$=uit$
end function
function multiply$( a$ , f )
 c = 0
 uit$ = ""
 for p = n to 1 step -1
   h = val( mid$( a$ , p , 1 ) ) * f + c
   c = int( h / 10 )
   uit$ = str$( h mod 10 ) + uit$
 next p
 multiply$ = uit$
end function

Now it prints lot's of zeros

Probably there is something wrong with subtract$
because
n=3
a$="105"
b$="016"
print subtract$(a$, b$)

prints
0199

[tsh73]

I kind of fixed (?) subtract$
function subtract$( a$ , b$ )
 b = 0
 uit$ = ""
 for p = n to 0 step -1
   a = val( mid$( a$ , p , 1 ) )
   b = val( mid$( b$ , p , 1 ) )
   h = a - b + 10 - c
   c = b>a
'    print a, b, h, c
   uit$ = str$( h mod 10 ) + uit$
 next p
 subtract$ = uit$
end function

Now I don't like divide 'cause it says
n=3
b$="016"
print divide$( b$ , 2 )

503

[tenochtitlanuk]

Will be interested in the finished version.
If others are interested in Pi, it's worth looking at the version currently on Rosetta Code LB area, or mine on my website- looks like I wrote that version in 2002!