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1、File:BPL_For_APL_Users.docAuthor:J.M.SmeenkRevision:5/23/0912:06:22AMBPL--ALanguageDerivedfromAPLBPLusesASCIItokensandwordsratherthantheGreekandothersymbolsofAPL,becausetheAPLalphabetisforeigntomostusers,isdifficulttotypeandedit,andislessexpandablethanapractically
2、infinitesetofkeywords.BPLhasmanymorebuilt-insystemvariablesandfunctionsthanAPL;APLphilosophytendstodesigneverythingfrombasiccomponents,butBPLphilosophyrecognizestheneedforanintegratedenvironmentoffunctionsthatallowforeasierconceptualization.Forexample,theAPL-1take
3、rhoMATRIXrequiresmorementalstepsbythereadertounderstandthantheBPLnumrowsMATRIX.BPLingeneralattemptstoreduceidiomaticprogrammingbyprovidingastandardizedandoptimizedsetoffunctions.Mathematiciansdonottypicallythinkintermsofprimitiveoperations,butratherintermsofoperat
4、ionsderivedfromprimitiveoperations,andonegoalofBPListobeatoolofthoughtsuitableformathematicsandcomputerscienceclasses.Thus,BPLhasoptionalhierarchieswhereasAPLeschewshierarchies.ABPLnumericscalarisusuallywritteninthegeneralform-1.2'-3&-4.5'-6(for-1.2x10^-3+ix-4.5x1
5、0^-6);alternate-baseconstantsaresimilarbutbeginwitha0andusethelettersA-Z(e.g.-0AB.8for171.5inbase16;thebaseisindicatedinasystemvariable);double-precisionconstantsaresimilarbutuseadoubledecimalpoint(e.g.3..14159);vectorsandhigher-orderarraysareconstructedsimilartoA
6、PL.BPLliteraldataislikeAPLliteraldataexceptthatdoublequotesareusedinsteadofsinglequotes.BPL'sgroundedsystemofnestedarraysarewrittenwithbracesenclosingheterogeneousdataseparatedbycommas(e.g.{"PQ",23#5,{},{{"R"}}});omittedarraysarepermittedtoshowthatdataisunavailabl
7、eorinapplicable.BPLusernamesbeginwithA-Z(e.g.MyVar1,X_Y_Z3)whileBPLsystemnamesbeginwitha-z(e.g.sin,base,sort_)orarecomposedofsymbolcombinations.Allsystemfunctionsareeitherniladic,monadic,ordyadic;systemfunctionsdonothavebothmonadicanddyadicusesasinAPL.BPLexpressio
8、nsarecomputedinright-to-leftorderwithnoprecedence,justlikeAPL,butsettingthesystemvariableprecedfromitsdefaultof0to1modifiesexecutionordertoresembletheor
