Stream merge: Difference between revisions
Content added Content deleted
(→version 2: changed program so that it can run under PC/REXX and Personal REXX, also insured that running a 2nd time doesn't corrupt the output file.) |
Walterpachl (talk | contribs) (→REXX version 1: reworked considering Gerard Schildberger's comments) |
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== {{header|REXX}} == |
== {{header|REXX}} == |
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===version 1=== |
===version 1=== |
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<lang rexx>/* |
<lang rexx>/* REXX *************************************************************** |
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* Merge 1.txt ... n.txt into |
* Merge 1.txt ... n.txt into all.txt |
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* 1.txt 2.txt 3.txt 4.txt |
* 1.txt 2.txt 3.txt 4.txt |
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* 1 19 1999 2e3 |
* 1 19 1999 2e3 |
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* 17 33 2999 3000 |
* 17 33 2999 3000 |
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* 8 500 3999 |
* 8 500 3999 RC task STREAM MERGE |
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**********************************************************************/ |
**********************************************************************/ |
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done.=0 /* done.i=1 indicates file exhausted */ |
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n=4 |
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p.='' /* for test of sort error */ |
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high='ffff'x |
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Do i=1 By 1 /* check files for existence */ |
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p.='' |
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Do i=1 To n |
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f.i=i'.txt' |
f.i=i'.txt' |
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If lines(f.i)=0 Then Leave |
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| ⚫ | |||
Call get i /* and read first line of each*/ |
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End |
End |
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n=i-1 /* we have n input files */ |
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Do Forever |
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done.0=n /* and all must be used */ |
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min=high |
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say n 'Input files' |
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oid='all.txt' |
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If lines(oid)>0 Then Do /* output file exists */ |
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| ⚫ | |||
Do Until wordpos(answer,'Y N')>0 |
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Say 'file' oid 'exists. May it be replaced?' |
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Pull answer |
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| ⚫ | |||
| ⚫ | |||
'erase' oid |
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| ⚫ | |||
Say 'Ok, we give up' |
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| ⚫ | |||
| ⚫ | |||
End |
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say oid 'is the output file' /* we'll create it now */ |
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Do Until done.0=0 |
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imin=0 /* index of next source */ |
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Do i=1 To n |
Do i=1 To n |
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If |
If done.i=0 Then Do /* file i still in use */ |
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If imin=0 Then Do /* it's the first in this loop*/ |
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| ⚫ | |||
imin=i /* next source */ |
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| ⚫ | |||
min=x.i /* element to be used */ |
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| ⚫ | |||
Else Do /* not the first */ |
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If x.i<<min Then Do /* avoid numerical comparison */ |
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imin=i /* next source */ |
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min=x.i /* element to be used */ |
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| ⚫ | |||
End |
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End |
End |
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End |
End |
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If imin<>0 Then Do /* found next source */ |
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| ⚫ | |||
Call o x.imin |
Call o x.imin /* use its element */ |
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Call get imin |
Call get imin /* get next element */ |
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/* or set done.imin */ |
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| ⚫ | |||
| ⚫ | |||
Call lineout oid |
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| ⚫ | |||
End |
End |
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Else /* no more elements */ |
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Call lineout oid /* close output file */ |
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End |
End |
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'type' oid |
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Exit |
Exit |
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get: Procedure Expose f. x. |
get: Procedure Expose f. x. p. done. |
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/********************************************************************* |
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* Get next element from file ii or set done.ii=1 if file is exhausted |
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*********************************************************************/ |
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Parse Arg ii |
Parse Arg ii |
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If lines(f.ii)=0 Then |
If lines(f.ii)=0 Then Do /* file ii is exhausted */ |
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done.ii=1 /* mark it as done */ |
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x.ii=high |
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done.0=done.0-1 /* reduce number of files tbd*/ |
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Else Do |
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End |
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x.ii=linein(f.ii) |
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Else Do /* there's more in file ii */ |
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If x.ii<<p.ii Then Do |
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x.ii=linein(f.ii) /* get next element (line) */ |
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If x.ii<<p.ii Then Do /* smaller than previous */ |
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Say 'Input file' f.ii 'is not sorted ascendingly' |
Say 'Input file' f.ii 'is not sorted ascendingly' |
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Say p.ii 'precedes' x.ii |
Say p.ii 'precedes' x.ii /* tell the user */ |
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Exit /* and give up */ |
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| ⚫ | |||
End |
End |
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p.ii=x.ii /* remember the element */ |
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p.ii=x.ii |
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End |
End |
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Return |
Return |
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o: Say arg(1) |
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o: Return lineout(oid,arg(1))</lang> |
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{{out}} |
{{out}} |
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<pre>1 |
<pre>1 |
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