reading and writing floats - GameCreators Forum

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netmon

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Posted: 10th Dec 2011 04:45

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How do you go about reading and writing floats and get them back accurately?

I need to be able to read 0.5 from a file as a string and write 0.5 as a float, just doesn't seem right that it's being rounded down to 0.00000

Basically, I am stripping an xml file of its tags, and writing out the values from that. I test the line to see if it's a number or not. if its a number i write it to one file with writefloat(), otherwise, writeline()

There has to be some workaround for this.

I can see the placement editor is able to do it, but I suspect it was written in C

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Dybing

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Location: Bergen, Norway

Posted: 10th Dec 2011 12:37

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You need to manually convert the string into a float by using some string functions to decide what is before and after the decimal marker (. or , depending on where in the world you live).

Basic logic of it is:

-read the string as is
-into a substring (let's call it temp1) you load all the numbers before the period or comma.
-into another substring (let's call it temp2) you load the numbers after the period or comma
-next you load a float with the value of temp1 + the value of temp2 divided 10 per decimal

I have such a function that reads a string from text-input and do the convertion into float for an application I've made. It basically reads the weight of a LED panel with 0 to 3 decimals. Code is supplied, but
is probably not that easy to follow, as I've not altered it for readability... But it do work

if textEdit = 7
                panelKg$ = ""
                Kg$ = ""
                Kg1$ = ""
                Kg2$ = ""
                KgDec = 0
                KgDiv# = 0
                KgFlag = 0

panelKg$ = getTextInput()
                c = len(panelKg$)

for b = 1 to c
                    if KgFlag = 0
                        Kg$ = mid(panelKg$, b, 1)
                        if Kg$ <> "." and kg$ <> ","
                            Kg1$ = Kg1$ + Kg$
                        endIf
                        if Kg$ = "." or Kg$ = ","
                            KgFlag = 1
                            inc b
                        endIf
                    endIf
                    if KgFlag = 1
                        if KgDec < 3
                            Kg2$ = Kg2$ + mid(panelKg$, b, 1)
                            inc KgDec
                        endIf
                    endIf
                next b

if KgDec = 0
                    KgDiv# = 1.00
                endIf
                if KgDec = 1
                    KgDiv# = 10.00
                endIf
                if KgDec = 2
                    KgDiv# = 100.00
                endIf
                if KgDec = 3
                    KgDiv# = 1000.00
                endIf

panel[currPanel].kg# = val(kg1$) + (val(kg2$) / KgDiv#)
                SetTextString(15, str(panel[currPanel].kg#, 2))
                textEdit = 0

endIf

+ Code Snippet

if textEdit = 7
                panelKg$ = ""
                Kg$ = ""
                Kg1$ = ""
                Kg2$ = ""
                KgDec = 0
                KgDiv# = 0
                KgFlag = 0

                panelKg$ = getTextInput()
                c = len(panelKg$)

                for b = 1 to c
                    if KgFlag = 0
                        Kg$ = mid(panelKg$, b, 1)
                        if Kg$ <> "." and kg$ <> ","
                            Kg1$ = Kg1$ + Kg$
                        endIf
                        if Kg$ = "." or Kg$ = ","
                            KgFlag = 1
                            inc b
                        endIf
                    endIf
                    if KgFlag = 1
                        if KgDec < 3
                            Kg2$ = Kg2$ + mid(panelKg$, b, 1)
                            inc KgDec
                        endIf
                    endIf
                next b

                if KgDec = 0
                    KgDiv# = 1.00
                endIf
                if KgDec = 1
                    KgDiv# = 10.00
                endIf
                if KgDec = 2
                    KgDiv# = 100.00
                endIf
                if KgDec = 3
                    KgDiv# = 1000.00
                endIf

                panel[currPanel].kg# = val(kg1$) + (val(kg2$) / KgDiv#)
                SetTextString(15, str(panel[currPanel].kg#, 2))
                textEdit = 0

            endIf

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netmon

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Posted: 10th Dec 2011 14:06

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Thanks. After I woke up this morning and thought more about it more, I realized I was going to have to do just this.

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Mobiius

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Joined: 27th Feb 2003

Location: The Cold North

Posted: 10th Dec 2011 18:14

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Why not just write it as a float? Or read it in an store it like so:
Float# = Val( ReadString( File ) )

My signature is NOT a moderator plaything! Stop changing it!

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Dybing

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Joined: 12th Sep 2011

Location: Bergen, Norway

Posted: 11th Dec 2011 22:13 Edited at: 11th Dec 2011 22:25

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Quote: "Why not just write it as a float? Or read it in an store it like so:
Float# = Val( ReadString( File ) )"

The problem is, that val() will only return an integer, no matter what you do. Unless they've changed it in a patch, and I've not caught it in one of the patch-notes.

So AFAIK:

myString$ = "1.4"
myFloat# = val(myString$)
print myFloat#

will output 1, not 1.4

Thus the need to "wash" the string to extract the numbers before and after the decimal-point.

Perhaps not that crucial with file i/o if you know you'll be reading a float, you just do so as you suggest. But for user-input there is no ready option, apart from a piece of code similar to what I showed in my previous post (though I'm sure it could be made more elegant. I tend to brute-force my way through a problem step by step rather than spend time on efficient and pretty code

)

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netmon

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Posted: 12th Dec 2011 01:33

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Here's my reval function, it looks to see if it's a float or not.

function findValPos(s$,ch$)

pos = -1
    l = len(s$)
    for i = 1 to l
        c$ = mid(s$,i,1)
        if c$ = ch$
            pos = i
            exit
        endif
    next i

//if pos =-1 value not found
endfunction pos

function reVal(s$, prec)
    //check if a . is in the string, if not exit with int(s$)
    isNeg = 0
    result# = 0.0
    pos = findValPos(s$,".")

if pos = -1
        // must be an integer
        retval# = val(s$)
        exitfunction retval#
    endif

// check if first character is a negative sign
    if mid(s$,1,1) = "-"
        isNeg = 1
        s$ = mid(s$,2,len(s$)-1)
    endif

base = val(left(s$,pos-1))
    //print(base)
    d$ = right(s$,len(s$)-pos)
    //print("right - " + d$)
    decc = val(d$)

sz = len(d$)
    if sz > prec
        sz = prec
        decc = val(left(d$,sz))
        //print("final decc - "+str(decc))
    endif
    select sz
        case 1
            result# = 0.1
        endcase
        case 2
            result# = 0.01
        endcase
        case 3
            result# = 0.001
        endcase
        case 4
            result# = 0.0001
        endcase
        case 5
            result# = 0.00001
        endcase
        case 6
            result# = 0.000001
        endcase

endselect

reval# = decc * result#
    reval# = base + reval#
    if isNeg = 1 then reval# = reval# * -1.0

endfunction reval#

+ Code Snippet

function findValPos(s$,ch$)

    pos = -1
    l = len(s$)
    for i = 1 to l
        c$ = mid(s$,i,1)
        if c$ = ch$
            pos = i
            exit
        endif
    next i

//if pos =-1 value not found
endfunction pos

function reVal(s$, prec)
    //check if a . is in the string, if not exit with int(s$)
    isNeg = 0
    result# = 0.0
    pos = findValPos(s$,".")

    if pos = -1
        // must be an integer
        retval# = val(s$)
        exitfunction retval#
    endif

    // check if first character is a negative sign
    if mid(s$,1,1) = "-"
        isNeg = 1
        s$ = mid(s$,2,len(s$)-1)
    endif


    base = val(left(s$,pos-1))
    //print(base)
    d$ = right(s$,len(s$)-pos)
    //print("right - " + d$)
    decc = val(d$)

    sz = len(d$)
    if sz > prec
        sz = prec
        decc = val(left(d$,sz))
        //print("final decc - "+str(decc))
    endif
    select sz
        case 1
            result# = 0.1
        endcase
        case 2
            result# = 0.01
        endcase
        case 3
            result# = 0.001
        endcase
        case 4
            result# = 0.0001
        endcase
        case 5
            result# = 0.00001
        endcase
        case 6
            result# = 0.000001
        endcase

    endselect

    reval# = decc * result#
    reval# = base + reval#
    if isNeg = 1 then reval# = reval# * -1.0

endfunction reval#

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