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data_20without_20data [2018/03/31 13:19] – external edit 127.0.0.1data_20without_20data [2024/01/05 00:22] (current) – external edit 127.0.0.1
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 //By JGH, May-2006.//\\  It is common for programs to put commonly used data in **DATA** statements which are then read into a set a variables at startup. A classic example is the names of months:\\  //By JGH, May-2006.//\\  It is common for programs to put commonly used data in **DATA** statements which are then read into a set a variables at startup. A classic example is the names of months:\\ 
 +<code bb4w>
         DIM mon$(12)         DIM mon$(12)
         RESTORE         RESTORE
         FOR mon%=1 TO 12:READ mon$(mon%):NEXT mon%         FOR mon%=1 TO 12:READ mon$(mon%):NEXT mon%
         DATA Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec         DATA Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec
 +</code>
 This has a few immediate disadvantages:\\  This has a few immediate disadvantages:\\ 
  
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   * The **DATA** pointer is modified, unless **LOCAL**ised   * The **DATA** pointer is modified, unless **LOCAL**ised
 \\  You can avoid the **DATA** pointer being modified by doing the following:\\ \\  \\  You can avoid the **DATA** pointer being modified by doing the following:\\ \\ 
 +<code bb4w>
         DIM mon$(12)         DIM mon$(12)
         mon$() = "","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"         mon$() = "","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"
 +</code>
 but the data is still held in memory twice.\\ \\  An alternative for small bits of fixed data like this is to hold them in a string:\\  but the data is still held in memory twice.\\ \\  An alternative for small bits of fixed data like this is to hold them in a string:\\ 
 +<code bb4w>
         DEF FNmon(mon%)=MID$("JanFebMarAprMayJunJulAugSepOctNovDec",mon%*3-2,3)         DEF FNmon(mon%)=MID$("JanFebMarAprMayJunJulAugSepOctNovDec",mon%*3-2,3)
 +</code>
 This has several advantages:\\  This has several advantages:\\ 
  
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   * The **DATA** pointer is not affected   * The **DATA** pointer is not affected
 \\  This can even be done for data that at first sight doesn't look like fixed data:\\  \\  This can even be done for data that at first sight doesn't look like fixed data:\\ 
 +<code bb4w>
         DEF FNmonth(mon%) \         DEF FNmonth(mon%) \
         \ =MID$("JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember", \         \ =MID$("JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember", \
         \ VALMID$("010816212629333743525967",mon%*2-1,2), \         \ VALMID$("010816212629333743525967",mon%*2-1,2), \
         \ VALMID$("785534469788",mon%,1))         \ VALMID$("785534469788",mon%,1))
 +</code>
 The first **VALMID$** string is a series of initial start positions of the month name strings for each month. The second **VALMID$** string is the length of each month name.\\ \\  Note: the example functions only give valid results for valid month numbers. The first **VALMID$** string is a series of initial start positions of the month name strings for each month. The second **VALMID$** string is the length of each month name.\\ \\  Note: the example functions only give valid results for valid month numbers.
data_20without_20data.1522502354.txt.gz · Last modified: 2024/01/05 00:18 (external edit)