CP/M/CPM_CDROM.iso/lambda/soundpot/f/if10.lbr/IF.DZC/IF.DOC

Text File | 1993-10-26 | 8.1 KB | 265 lines

                           IF-ELSE-ENDIF Documentation


                                 For Version 1.0


                            Written by:  Marc C. Brooks
                                         1124 Redman Rd.
                                         St. Louis, MO 63043
                                         [phone] (voice)




                                  INTRODUCTION

             I╞á anΣ it≤ companioε program≤ (ELSE¼á ENDI╞ anΣá GOTO⌐á arσ ì
        direc⌠á out-growth≤á oµá DaviΣ Kirkland'≤ versioε oµá thσá SKIPI╞ ì
        prograφ a≤ printeΣ iε Dr«á Dobb'≤ Journal«á  The∙ sharσ mucΦ codσ ì
        witΦá thσ SKIPI╞ anΣ ╔ aφ eternall∙ gratefu∞ fo≥á Mr«á Kirkland'≤ ì
        inspiration.

             I╞á i≤ designeΣ t∩ allo≈ conditiona∞ executioε oµ statement≤ ì
        withiεá ß CP/═ submi⌠ file«á  Becausσ oµ thσ methoΣ useΣ t∩á ski≡ ì
        statement≤ iε thσ submi⌠ file¼á I╞ canno⌠ bσ useΣ iε CP/M+«á  Fo≥ ì
        al∞ othe≥ version≤ oµ CP/M-80¼á though¼á I╞ lend≤ thσ versitilit∙ ì
        oµá thσ standarΣ structureΣ programminτ construc⌠á IF-ELSE-ENDIF«  ì
        GOT╧ i≤ ß companioε prograφ whosσ neeΣ wa≤ discovereΣ whilσ usinτ ì
        IF«á  I⌠á allow≤á forwarΣ (backwarΣ i≤ impossible⌐ jump≤á iεá thσ ì
        submi⌠ t∩ labeleΣ points.

             IF¼ ELSE¼ anΣ GOTO¼ wheε executσ froφ thσ CC╨ bu⌠ no⌠ withiε ì
        ßá submi⌠á file¼áá wil∞á explaiεá thei≥á usσá anΣá syntax«á  Thi≤ ì
        document'≤á maiε purposσ i≤ t∩ givσ example≤ iε thσ usσ oµá thesσ ì
        four programs.


















        Page 1 of 4                          IF Documentation Version 1.0










        I.  IF Summary

             I╞ i≤ thσ maiε prograφ fo≥ thi≤ package«  I⌠ make≤ decision≤ ì
        oεá whicΦ logica∞ brancΦ oµ thσ submi⌠ shoulΣ bσ taken«á  Iµá thσ ì
        conditioε specifieΣ b∙ thσ I╞ commanΣ i≤ true¼ al∞ command≤ u≡ t∩ ì
        thσá matchinτá ELS┼ o≥ ENDI╞ wil∞ bσ executed«á  Iµá aεá ELS┼á i≤ ì
        encountereΣá whilσ executinτ command¼á t∩ followinτ command≤ wil∞ ì
        bσá skippeΣá unti∞ thσ matchinτ ENDI╞á i≤á encountered«á  Iµá thσ ì
        conditioεá i≤á false¼á command≤ u≡ t∩ anΣ includinτ thσá matchinτ ì
        ELS┼ (iµ i⌠ exists⌐ o≥ ENDI╞ arσ skipped«á  I╞ ha≤ fivσá command≤ ì
        whicΦ decidσ thσ fatσ oµ thσ submit«  The∙ are:

             A[mbig] fn     Iµá thσ fε whicΦ appear≤ oε thσ commanΣá linσ ì
        áááááááááááááááááááái≤á aεá ambiguou≤ filσ referencσá  (i.e«á onσ ì
        ááááááááááááááááááááwitΦ aε ¬ o≥ ┐ iε it⌐ thσ conditioε i≤ true.

        áááááE[xists] fn    Iµ thσ filσ referenceΣ b∙ thσ fε giveε oε thσ ì
        áááááááááááááááááááácommand line exists, the condition is true.

             M[issing] fn   Iµ thσ filσ referenceΣ b∙ thσ fε giveε oε thσ ì
        áááááááááááááááááááácommanΣ linσ caε no⌠ bσ found¼á thσ conditioε ì
        áááááááááááááááááááái≤ true.

             N[ull] (fn)    Iµá thσ fε itselµ i≤ missinτ froφ thσ commanΣ ì
        ááááááááááááááááááááline¼á thσ conditioε i≤ true«á  Notσ tha⌠ thσ ì
        ááááááááááááááááááááparathesi≤ '()º d∩ NO╘ appea≥ iε actua∞ use.

        áááááZ[ero] fn      Iµ thσ filσ referenceΣ b∙ thσ fε giveε oε thσ ì
        áááááááááááááááááááácommanΣá linσ caε no⌠ bσ founΣ o≥ i≤ oµá zer∩ ì
        áááááááááááááááááááálength¼ thσ conditioε i≤ true.

        Notσ tha⌠ onl∙ thσ firs⌠ characte≥ oµ thσ keyworΣ (┴ fo≥ Ambiτ o≥ ì
        whateve≥á i≤á significant«á  Al∞á othe≥ character≤ oµá thσá firs⌠ ì
        paramete≥ arσ ignored«á  Thσ seconΣ paramete≥ MUS╘ exis⌠ fo≥á al∞ ì
        commanΣá excep⌠ witΦ thσ Nul∞ command«á  Iµ aε invaliΣ keyworΣ i≤ ì
        giveεá o≥ thσ fε i≤ missinτ wheε needed¼á I╞ wil∞ givσá aεá erro≥ ì
        messagσá anΣ ski≡ t∩ thσ matchinτ ENDI╞ statement«á  Iµ an∙ othe≥ ì
        error occurs, IF will abort the submit.


        II.  ELSE Summary

             ELS┼á i≤ ß prograφ tha⌠ automaticall∙ skip≤ al∞ command≤á u≡ ì
        t∩á anΣá includigεá thσ matchinτ IF«á  I⌠á i≤á skippeΣá wheεá thσ ì
        preceedinτá I╞á i≤ false¼á s∩ i⌠ wil∞ onl∙ bσ executeΣá wheεá thσ ì
        preceedinτ I╞ i≤ true«á  Iε tha⌠ case¼á ELS┼ shoulΣ ski≡ thσ ELS┼ ì
        clausσá u≡á t∩ thσ ENDI╞ marker«á  Fo≥ tha⌠ reason¼á ELS┼á alway≤ ì
        skip≤ t∩ thσ matchinτ ENDIF«á  IF-ELSE-ENDI╞ group≤ ma∙ bσ nesteΣ ì
        t∩á an∙á deptΦá anΣ ELS┼ wil∞ ski≡ t∩á it≤á ENDIF«á  Iµá ELS┼á i≤ ì
        executeΣ b∙ thσ CC╨ outsidσ ß submit¼ i⌠ wil∞ explaiε it≤ usσ anΣ ì
        exit«  Iµ i⌠ run≤ int∩ an∙ errors¼ i⌠ wil∞ terminatσ thσ submit.




        Page 2 of 4                          IF Documentation Version 1.0










        III.  ENDIF Summary

             ENDI╞ i≤ jus⌠ ß place-marke≥ fo≥ I╞ anΣ ELSE¼ bu⌠ i⌠ mus⌠ bσ ì
        aεá executablσá prograφ becausσ i⌠ wil∞ bσ loadeΣ ever∙ timσá thσ ì
        ELS┼ clausσ oµ aε I╞ i≤ executed«á  Iε it≤ curren⌠ form¼á i⌠ jus⌠ ì
        returns to the CCP.


        IV.  GOTO Summary

             GOT╧ i≤ useΣ t∩ providσ unconditiona∞ skippinτ oµ step≤ iε ß ì
        submi⌠ procedure«  T∩ usσ it¼ jus⌠ pu⌠ GOT╧ 'labelº iε thσ submi⌠ ì
        prograφ wherσ desired«á  Somewherσ late≥ iε thσ submit¼á placσá ß ì
        labe∞á a≤ ß commen⌠ line«á  Label≤ takσ thσ forφ oµ an∙ strinτ oµ ì
        non-whitespacσ character≤ terminateΣ b∙ thσ enΣ oµ thσ linσ o≥á ß ì
        whitespacσá character«á  Whitespacσ character≤ arσ an∙ character≤ ì
        lowe≥ iε thσ ASCI╔ collatinτ sequencσ thaε '!º (i.e«á space¼ tab¼ ì
        etc.)  Some examples of GOTO are:

                  GOTO END-OF-COMPILE
                  GOTO SKIP           terminate the rest of the submit
                  GOTO 1200

             Iε thσ seconΣ example¼ thσ tex⌠ followinτ thσ worΣ 'SKIPº i≤ ì
        al∞á ignored«á  Thσá correspondinτ t∩ thσ abovσá GOT╧á statement≤ ì
        might look like this:

                  ;END-OF-COMPIL┼  Al∞ thσ passe≤ oµ thσ compilσ arσ done
                  ;SKIP
                  ;1200

             Oncσá again¼á iε thσ firs⌠ example¼á thσ tex⌠ followinτá thσ ì
        labe∞ i≤ completel∙ ignored«  Also¼ duσ t∩ limitation≤ withiε thσ ì
        CCP, the case of the label characters is not significant.





















        Page 3 of 4                          IF Documentation Version 1.0










        V.  EXAMPLES

        Example 1.     pp -o edit.tm1 edit.c
                       p1 -o edit.tm2 edit.tm1
                       era edit.tm1
                       IF ZERO EDIT.TM2      did the p1 passed find errors ?
                            era edit.tm2
                            GOTO LIST-FILE
                       ELSE
                            p280 -o edit.s edit.tm2
                            era edit.tm2
                            as80 edit.s
                            era edit.s
                            link -o edit.com edit.o
                       ENDIF
                       IF ZERO EDIT.COM       did the link fail ?
                            ;LIST-FILE      ; list the source file
                            list edit.c
                       ENDIF

        Example 2:     IF Null $1
                            ;ERROR -- You must supply a file to be compiled
                       ELSE
                       IF Ambig $1
                            ;ERRO╥á-- Yo⌡áma∙áno⌠ usσáambiguou≤áfilσ names
                       ELSE
                       IF Missing $1.bas
                            ;ERROR -- I can't find $1
                       ELSE
                            ; all okay so lets compile the program
                            CB80 $1.bas $3
                            LK80 $1 my.lib
                            IF Null $2
                            ELSE
                                 list $1.bas
                            ENDIF
                       ENDIF
                       ENDI╞       ╗ thesσ tw∩ ENDIF'≤ aren'⌠ necessary,
                       ENDIF       ; just good programming.
















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