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Bemerkungen

Die COBOL SEARCH Anweisung gibt es in zwei Formen. Lineares SEARCH oben nach unten und ein binärer SEARCH ALL Algorithmus. Binäres SEARCH ALL setzt eine sortierte Tabelle voraus, die für eine binäre Suche ohne Elemente geeignet ist.

SEARCH-Anweisung

SEARCH-Anweisungssyntaxdiagramm

Lineares SUCHEN

Lineares SEARCH-Syntaxdiagramm

Binär Alle suchen

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Lineares SUCHEN

GCobol >>SOURCE FORMAT IS FIXED
      *> ***************************************************************
      *> Purpose:   Demonstration of the SEARCH verb
      *> Tectonics: cobc -x searchlinear.cob
      *> ***************************************************************
       identification division.
       program-id. searchlinear.

       data division.

       working-storage section.
       01 taxinfo.
          05 tax-table occurs 4 times indexed by tt-index.
             10 province       pic x(2).
             10 taxrate        pic 999v9999.
             10 federal        pic 999v9999.
       01 prov                 pic x(2).
       01 percent              pic 999v9999.
       01 percentage           pic zz9.99.

      *> ***************************************************************
       procedure division.
       begin.

      *> ***************************************************************
      *> Sample for linear SEARCH, requires INDEXED BY table
      *> populate the provincial tax table;
      *>  *** (not really, only a couple of sample provinces) ***
      *> populate Ontario and PEI using different field loaders
       move 'AB' to province(1)
       move 'ON' to province(2)
       move 0.08 to taxrate(2)
       move 0.05 to federal(2)
       move 'PE00014000000000' to tax-table(3)
       move 'YT' to province(4)

      *> Find Ontario tax rate
       move "ON" to prov
       perform search-for-taxrate

      *> Setup for Prince Edward Island
       move 'PE' to prov
       perform search-for-taxrate

      *> Setup for failure
       move 'ZZ' to prov
       perform search-for-taxrate

       goback.
      *> ***************************************************************

       search-for-taxrate.
           set tt-index to 1
           search tax-table
               at end display "no province: " prov end-display
               when province(tt-index) = prov
                   perform display-taxrate
           end-search
       .

       display-taxrate.
           compute percent = taxrate(tt-index) * 100
           move percent to percentage
           display
               "found: " prov " at " taxrate(tt-index)
               "," percentage "%, federal rate of " federal(tt-index)
           end-display
       .

       end program searchlinear.

Binär Alle suchen

GCobol >>SOURCE FORMAT IS FIXED
      *> ***************************************************************
      *> Purpose:   Demonstration of the SEARCH ALL verb and table SORT
      *> Tectonics: cobc -x -fdebugging-line searchbinary.cob
      *> ***************************************************************
       identification division.
       program-id. searchbinary.

       environment division.
       input-output section.
       file-control.
           select optional wordfile
           assign to infile
           organization is line sequential.

       data division.
       file section.
       fd wordfile.
           01 wordrec          pic x(20).

       working-storage section.
       01 infile               pic x(256) value spaces.
          88 defaultfile       value '/usr/share/dict/words'.
       01 arguments            pic x(256).

      *> Note the based clause, this memory is initially unallocated
       78 maxwords             value 500000.
       01 wordlist             based.
          05 word-table occurs maxwords times
              depending on wordcount
              descending key is wordstr
              indexed by wl-index.
             10 wordstr        pic x(20).
             10 wordline       usage binary-long.
       01 wordcount            usage binary-long.

       01 file-eof             pic 9 value low-value.
          88 at-eof            value high-values.

       01 word                 pic x(20).

      *> ***************************************************************
       procedure division.
       begin.

      *> Get the word file filename
       accept arguments from command-line end-accept
       if arguments not equal spaces
           move arguments to infile
       else
           set defaultfile to true
       end-if

      *> ***************************************************************
      *> Try playing with the words file and binary SEARCH ALL
      *>   requires KEY IS and INDEXED BY table description

      *> Point wordlist to valid memory
       allocate wordlist initialized

       open input wordfile

       move low-value to file-eof
       read wordfile
           at end set at-eof to true
       end-read

       perform
           with test before
           until at-eof or (wordcount >= maxwords)
               add 1 to wordcount
               move wordrec to wordstr(wordcount)
               move wordcount to wordline(wordcount)
               read wordfile
                   at end set at-eof to true
               end-read
       end-perform

       close wordfile

      *> ensure a non-zero length table when allowing optional file
       evaluate true                  also file-eof
           when wordcount = 0         also any
               move 1 to wordcount
               display "No words loaded" end-display
           when wordcount >= maxwords also low-value
               display "Word list truncated to " maxwords end-display
       end-evaluate

    >>D display "Count: " wordcount ": " wordstr(wordcount) end-display

      *> Sort the words from z to a
       sort word-table on descending key wordstr

      *> fetch a word to search for
       display "word to find: " with no advancing end-display
       accept word end-accept

      *> binary search the words for word typed in and display
      *> the original line number if/when a match is found
       set wl-index to 1
       search all word-table
           at end
               display
                   word " not a word of " function trim(infile)
               end-display
           when wordstr(wl-index) = word
               display
                   word " sorted to " wl-index ", originally "
                   wordline(wl-index) " of " function trim(infile)
               end-display
       end-search

      *> Release memory ownership
       free address of wordlist

       goback.
       end program searchbinary.


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