/** rexx:breakthings.rexx * * This program demonstrates what happens if you first add * our almost function host, rexx:testhost.rexx with a lower * priority than rexxmathlib.library, and then what happens * if you change things so that TESTPORT is added to the library * list with a higher priority than rexxmathlib.library. * In the first case, since TESTPORT gets all functions only * after everyone has rejected them, calls like sin(2) succeed. * In the second case no call ever gets to rexxmathlib.library * because one has to do more than reply to the RexxMessage * in order for the REXX host process to keep looking for a match * **/ /* * Make sure all libraries are present */ addrexxlib /* * First open a requester telling the user what is about to * happen. The first two arguments to the request function * are the x and y coordinates of the upper left hand corner * of the window. The next argument is the message to be * displayed. Multi-line messages can be composed by using * a \ to indicate a carriage return. I tend to compose the * message first and then call the function */ message = "This is a demo to show how things break when\" message = message||"you add a broken function host or non-existent\" message = message||"library to ARexx's library list\\" message = message||" Should I continue? " /* * Put up a simple requester with an OKAY or ABORT button * the call is * * request(xpos,ypos,message,,okay text,abort text) * * The two ,, together are to indicate that this is not a * string requester. Clicking on the gadget that says Go On * returns OKAY, clicking on Abort returns nothing */ x = request(0,0,message,," Go On "," Abort ") if x ~="OKAY" then exit 0 /* * Start rexx:testhost running in a shell * Send the command to AREXX so it will run asynchronously */ address AREXX "work:articles/testhost.rexx" /* * Now check to see that TESTPORT has been opened, give it some * time. If it doesn't open then exit and use postmsg() to * inform the user what happened */ do i = 1 to 2 if ~showlist('p','TESTPORT') then call delay 20 else leave i end if i = 2 & ~showlist('p',TESTPORT) then do call postmsg(10,10,"Couldn't start rexx:testhost.rexx") call delay 80 call postmsg() exit 2 end /* * Add TESTPORT at a lower priority than rexxarplib,rexxmathlib,etc. * */ call addlib(TESTPORT,-1) /* * First show that a call to postnote works just fine * by executing the call to postnote() */ message = "TESTPORT has been added to the library list \" message = message||"at priority -1. We can now do \\" message = message||" call postnote() \\" message = message||"and a window should open, hang around, and \" message = message||"then close.\" x = request(0,0,message,," Show Me "," Abort ") if x ~= OKAY then exit 0 call postnote() message = "Well, that worked okay, now how about calling a math\" message = message||"function from rexxmathlib.library" call delay 30 x = request(0,0,message,," Do It "," Abort ") if x ~= OKAY then exit 0 /* * Get a list of all entries on the library list and reformat * them into a column. Define nl to be the console * linefeed character to make things easy. */ nl = "0a"x libcol = "" liblist = show('l') do until liblist = "" parse var liblist nextentry liblist libcol = libcol" "||nextentry||"0a"x end /* * Call sin(3) which is supplied by rexxmathlib.library */ sin3 = sin(3) /* * format the message to appear in the window */ message = "ARexx's current library list contains"nl"the following"nl||nl message = message||libcol||nl||nl message = message||"So a call to rexxmathlib should work fine."nl||nl message = message||"The result of typing"||nl||nl message = message||" "||"say sin(3)"||nl message = message||" > "sin3"0a"x /* * Use a console window for output of the information * post a requester above it to ask for directions. Also, * since nothing happens until the user clicks on something * this provides a pause in the program. */ call open(DEMOWINDOW,"con:0/65/400/160/Demo") call writech(DEMOWINDOW,message) message = " So far so good. The only thing that remains\" message = message||" is to see how things break. Want to go on?" x = request(0,0,message,," Continue "," Quit ") call close(DEMOWINDOW) if x ~= OKAY then exit 0 /* * User clicked on Continue so now let us remove rexxmathlib and * TESTPORT from the library list and add it back at a lower priority * than TESTPORT */ call remlib('rexxmathlib.library') call addlib('rexxmathlib.library',-2,-30,0) /* * Now show the reader what happens when you try and call sin(3) * in this situation * Since the call will break with an error return from function * which is an ARexx SYNTAX error we have to trap the error and * handle the condition ourselves, or our demo will stop */ libcol = "" liblist = show('l') do until liblist = "" parse var liblist nextentry liblist libcol = libcol" "||nextentry||"0a"x end SIGNAL ON SYNTAX sin3 = sin(3) CONTINUE: message = "Well, this time the library list looks like "nl||nl message = message||libcol||nl||nl message = message||"and so now the line "nl message = message||" say sin(3) "nl||nl message = message||"produces an error message "nl message = message||" > "errormess call open(DEMOWINDOW,"con:0/48/383/160/Demo") call writech(DEMOWINDOW,message) x = request(0,0,"Well that's it. Click on the close gadget \to exit the program ") /* * Time to clean things up and put them back the way they were */ call close(DEMOWINDOW) call closetestport() call remlib(TESTPORT) call remlib('rexxmathlib.library') call addlib('rexxmathlib.library',0,-30,0) exit 0 SYNTAX: errormess = errortext(rc); signal CONTINUE: return