31 lines
2.4 KiB
Rexx
31 lines
2.4 KiB
Rexx
/*REXX program demonstrates the classic hash join algorithm for two relations. */
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S. = ; R. =
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S.1 = 27 'Jonah' ; R.1 = "Jonah Whales"
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S.2 = 18 'Alan' ; R.2 = "Jonah Spiders"
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S.3 = 28 'Glory' ; R.3 = "Alan Ghosts"
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S.4 = 18 'Popeye' ; R.4 = "Alan Zombies"
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S.5 = 28 'Alan' ; R.5 = "Glory Buffy"
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hash.= /*initialize the hash table (array). */
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do #=1 while S.#\==''; parse var S.# age name /*extract information*/
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hash.name=hash.name # /*build a hash table entry with its idx*/
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end /*#*/ /* [↑] REXX does the heavy work here. */
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#=#-1 /*adjust for the DO loop (#) overage.*/
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do j=1 while R.j\=='' /*process a nemesis for a name element.*/
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parse var R.j x nemesis /*extract the name and its nemesis. */
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if hash.x=='' then do; #=# + 1 /*Not in hash? Then a new name; bump #*/
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S.#=',' x /*add a new name to the S table. */
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hash.x=# /* " " " " " " hash " */
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end /* [↑] this DO isn't used today. */
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do k=1 for words(hash.x); _=word(hash.x, k) /*obtain the pointer.*/
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S._=S._ nemesis /*add the nemesis ──► applicable hash. */
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end /*k*/
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end /*j*/
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_='─' /*the character used for the separator.*/
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pad=left('', 4) /*spacing used in header and the output*/
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say pad center('age', 3) pad center("name", 20 ) pad center('nemesis', 30 )
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say pad center('───', 3) pad center("" , 20, _) pad center('' , 30, _)
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do n=1 for #; parse var S.n age name nems /*obtain information.*/
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if nems=='' then iterate /*No nemesis? Skip. */
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say pad right(age,3) pad center(name,20) pad center(nems,30) /*display an "S". */
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end /*n*/ /*stick a fork in it, we're all done. */
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