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Random Access Procedures

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Topic: Random Access Procedures (Read 103 times)

joker
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Re: Random Access Procedures
« Reply #9 on: Oct 22^nd, 2015, 2:40pm »

So, am I barking up the wrong tree and going to find out after I build a lot of stuff? I'd like to know the chances of success now! ;D

Code:

function(OpenRAF path$, filename$, fileHandle$, recordLen)
    ' file must exist?
    open filename$ for random as #fileHandle$ len = recordLen ' open and define record
end function
 
sub CloseRAF fileHandle$
    close #fileHandle$
end sub

function fileExists(path$, filename$)
    'dimension the array info$( at the beginning of your program
    'dim info$(10, 10)
    'if fileExists(DefaultDir$, "users.dat") then
    files path$, filename$, info$()
    fileExists = val(info$(0, 0)) 'non zero is true
end function

function SetRAFfields(fileHandle$, recordLen)
    'field lengths and field names have to be modified per program
    'call after OpenRAF
    'set the fields in RAF
    if (1+2+3+4) = recordLen then ' something to make one think about field lengths
        field #fileHandle$,_
            1 as field1$,_
            2 as field2$,_
            3 as field3$,_
            4 as field4$
        SetRAFfields = 0
    else
        SetRAFfields = 1 ' error condition
    endif
end function

« Last Edit: Oct 22^nd, 2015, 2:41pm by joker »

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Richard Russell
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Re: Random Access Procedures
« Reply #10 on: Oct 22^nd, 2015, 10:10pm »

on Oct 22^nd, 2015, 2:40pm, pnlawrence wrote:

Code:

    open filename$ for random as #fileHandle$ len = recordLen

That doesn't work (even in LBB!), you must use MAPHANDLE:

Code:

    open filename$ for random as #1 len = recordLen
    maphandle #1, fileHandle$

Richard.

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joker
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Re: Random Access Procedures
« Reply #11 on: Oct 23^rd, 2015, 10:45am »

Funny how the brain works! "#fileHandle$" has shown up in some of my searches, but not in that form.

I should have used/assumed the form fileHandle$ = "#" + {path} + fileName$.

Being generic is getting more difficult. I'm starting to wonder if its worth the time for my project.

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joker
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Re: Random Access Procedures
« Reply #12 on: Oct 23^rd, 2015, 11:04am »

Curses! That won't work either. Missing "#" in OPEN.

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Richard Russell
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Re: Random Access Procedures
« Reply #13 on: Oct 23^rd, 2015, 11:21am »

on Oct 23^rd, 2015, 11:04am, pnlawrence wrote:

Curses! That won't work either. Missing "#" in OPEN.

The code I listed does work - I tested it before posting as I always try to do. Here's the entire earlier demo from the 'Numeric field length RAF' thread modified to use a handle variable to prove that it can be done (in LBB):

Code:

    handle$ = "#MyFileHandle" ' the handle variable

    field1 = 1/3
    field2 = 1/3

    open "test.raf" for random as #1 len = 20
    maphandle #1, handle$
    field #handle$, 6 as field1, 14 as field2
    put #handle$, 1
    close #handle$

    open "test.raf" for random as #2 len = 20
    maphandle #2, handle$
    field #handle$, 6 as field1$, 14 as field2$
    get #handle$, 1
    close #handle$

    print chr$(34);field1$;chr$(34)
    print chr$(34);field2$;chr$(34)

This doesn't work in LB 4.04 or 4.5.0 so without LBB you really would be screwed.

Richard.

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joker
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Re: Random Access Procedures
« Reply #14 on: Oct 23^rd, 2015, 11:29am »

Thanks, Richard. I am studying every word you write.

This "library" seems to pass the RUN test (no program), but with an "incompatibility" error message.

EDIT: Well, of course it doesn't "RUN", because it has an "ERROR". The error message implies that it was somehow corrected, but there's no output.

Code:

function OpenRAF(path$, filename$, fileHandle$, recordLen)
    ' file must exist?
    open filename$ for random as #fileHandle$ len = recordLen ' open and define record
end function
 
sub CloseRAF fileHandle$
    close #fileHandle$
end sub

function fileExists(path$, filename$)
    'dimension the array info$( at the beginning of your program
    'dim info$(10, 10)
    'if fileExists(DefaultDir$, "users.dat") then
    files path$, filename$, info$()
    fileExists = val(info$(0, 0)) 'non zero is true
end function

function setRAFfields(fileHandle$, recordLen)
    'field lengths and field names have to be modified per program
    'call after OpenRAF
    'set the fields in RAF
    if (1+2+3+4) = recordLen then ' something to make one think about field lengths
        field #fileHandle$,_
            1 as field1$,_
            2 as field2$,_
            3 as field3$,_
            4 as field4$
        SetRAFfields = 0
    else
        SetRAFfields = 1 ' error condition
    endif
end function

« Last Edit: Oct 23^rd, 2015, 12:30pm by joker »

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joker
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Re: Random Access Procedures
« Reply #15 on: Oct 23^rd, 2015, 11:32am »

Let me paraphrase your comment ...

Quote:

... without LBB you really would be screwed.

Without LBB you really are screwed!

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Richard Russell
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Re: Random Access Procedures
« Reply #16 on: Oct 23^rd, 2015, 1:07pm »

on Oct 23^rd, 2015, 11:29am, pnlawrence wrote:

I am studying every word you write.

Apparently not acting upon however! :-)

Quote:

This "library" seems to pass the RUN test (no program), but with an "incompatibility" error message.

It still includes the line that doesn't work (either in LB or LBB):

Code:

    open filename$ for random as #fileHandle$ len = recordLen ' open and define record

I have twice listed the correct code, but for some reason you have failed to incorporate it.

You also have an endif where you meant end if.

Richard.

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joker
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Re: Random Access Procedures
« Reply #17 on: Oct 23^rd, 2015, 7:19pm »

At the risk of antagonizing Richard even further ... :D ... I do like to find the edges of proper operation.

LB reports a syntax error in the open line and LBB just says "Mistake!"

EDIT: Adding the "result =" bit-bucket for the FUNCTION makes the compilers happy.

Code:

path$ = ""
fileName$ = "myfile.txt"
fileHandle$ = "#file1"
recordLen = 10
field1$ = "1234"
field2$ = "1234"
field3$ = "1234"
field4$ = "1234"

' EDIT: openRAF(path$,fileName$,fileHandle$,recordLen)
result = openRAF(path$,fileName$,fileHandle$,recordLen)

put #fileHandle$, 1

call closeRAF fileHandle$

field1$ = ""
field2$ = ""
field3$ = ""
field4$ = ""

'EDIT: openRAF(path$,fileName$,fileHandle$,recordLen)
result = openRAF(path$,fileName$,fileHandle$,recordLen)

get #fileHandle$, 1

call closeRAF fileHandle$

print "1:  "; field1$
print "2:  "; field2$
print "3:  "; field3$
print "4:  "; field4$

end

sub closeRAF fileHandle$
    close #fileHandle$
end sub

function fileExists(path$, filename$)
    ' dimension the array info$( at beginning of program
    ' dim info$(10, 10)
    ' e.g. if fileExists(DefaultDir$, "users.dat") then
    files path$, filename$, info$()
    fileExists = val(info$(0, 0)) 'non zero is true
end function

function openRAF(path$, filename$, fileHandle$, recordLen)
    ' file must exist?
    ' fileExists(path$, filename$)
    ' fileHandle$ = "#yourFileHandle"
    open filename$ for random as #1 len = recordLen ' open and define record
    maphandle #1, fileHandle$
    openRAF = setRAFfields(fileHandle$, recordLen)
end function

function setRAFfields(fileHandle$, recordLen)
    'field lengths and field names have to be modified per program
    'call after openRAF
    'set the fields in RAF
    if (1+2+3+4) = recordLen then ' something to make one think about field lengths
        field #fileHandle$,_
            1 as field1$,_
            2 as field2$,_
            3 as field3$,_
            4 as field4$
        setRAFfields = 0
    else
        setRAFfields = 1 ' error condition
    end if
end function

« Last Edit: Oct 24^th, 2015, 10:06am by joker »

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Richard Russell
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Re: Random Access Procedures
« Reply #18 on: Oct 23^rd, 2015, 9:32pm »

on Oct 23^rd, 2015, 7:19pm, pnlawrence wrote:

LB reports a syntax error in the open line and LBB just says "Mistake!"

It may be that you have previously used another language which allows a function to be called without assigning the returned value to anything, but Liberty BASIC doesn't. If you want to call a function, but ignore the value it returns, you must assign it to something, for example:

Code:

    ignoreThis = openRAF(path$,fileName$,fileHandle$,recordLen)

Richard.

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joker
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Re: Random Access Procedures
« Reply #19 on: Oct 24^th, 2015, 09:51am »

Now, there's a difference between SUB and FUNCTION that I missed. Thanks!

« Last Edit: Oct 24^th, 2015, 09:51am by joker »

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Richard Russell
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Re: Random Access Procedures
« Reply #20 on: Oct 24^th, 2015, 10:40am »

on Oct 23^rd, 2015, 9:32pm, Richard Russell wrote:

If you want to call a function, but ignore the value it returns, you must assign it to something

I occasionally use this construction, to avoid creating a dummy variable, but it's a bit ugly (and relies on a 'feature' of LB/LBB that rem and ' are not always equivalent):

Code:

    if openRAF(path$,fileName$,fileHandle$,recordLen) then rem

Richard.

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