OpenEuphoria

2. Types and stuff

• Posted by Ad Rienks <Ad_Rienks at COMPUSERVE.COM> Apr 26, 1998
• 521 views

Falkon wrote:

>While we're on the subject of big numbers and structured data
>with limited types and all, I thought I'd share my big oopsie of
>the day.

>--------------------------------------- include get.e

>type Number( sequence string )
  sequence check
  check =3Dvalue( string )
> --make sure it's a valid object, and a number at that.    =

>if (check[1] =3D GET_SUCCESS) and atom( check[2] ) then       =

>    return( 1 )
  end if
  return( 0 )
 end type

>sequence test, currentcash
 test =3D "4 3x65 Fred"    --or howabout "4,685,736,552"?
 currentcash =3D value( test )

>If Number(test) then
    printf( 1, "%d",  currentcash[2] )
 else =

>  puts( 1, "Not a valid number" )
 end if
>----------------------------------------------------

>    Okay, quick, off the top of your head...what's the output? =

>Both of 'em evaluate to numbers.  The actual output though, is
>4.  In either case. After rereading the description of value()
>carefully, I realize it's supposed to work that way.  But I had
>_assumed_ that the first case would turn up a value of { 4,
>{3,'x',6,5}, "Fred" }  or even {4, "3x65", "Fred" } and
>therefore would fail the atom() check.    Just thought I'd share
>that...imagining the looks on peoples faces when they found out
>the national debt was $3.   

>Falkon

I think the following type definition should do the trick:

type number(sequence string)
    if compare(string, {}) =3D 0 then
        -- empty string is also not a valid number!
        return 0
    end if
    for n =3D 1 to length(string) do
        if not find(string[n], "0123456789.") then
            return 0
        end if
    end for
    -- if you 'fall through' the test, everything is alright
    return 1
end type

The above test is for decimal numbers, it's easy to test for integers jus=
t
by leaving out the period in the second element of the find function.
IMO a better solution would be to reprogram the type definition as a
function, that can be inside a loop, checking for good input. Actually no=

reprogramming is necessary, as a type definition is a special case of a
function.

-- example.ex
-- input routine

object input
input =3D {}      -- empty

while not number(input) do
    clear_screen()
    puts(1, "A number please")
    input =3D gets(0)
    -- the last or only character is always a newline!
    input =3D input[1..length(input) - 1]
end while

input =3D value(input)
input =3D input[2]
-- input contains a valid number now!
printf(1, "\nYour input was: %f", input)

Hope this helps,

Ad