puppybasic intro ch. 11 - decision making

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decision making                                                          
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                  an intro to puppybasic                                 
                                                                         
                  chapter 11: decision making                            
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
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decision making                                                          
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hey, now we make your programs smarter. right now your code does this:   
                                                                         
[do this.]                                                               
                                                                         
but we can make it so smart, it'll know whether to or not!               
                                                                         
[do this... but not unless i want you to.]                               
                                                                         
you just have to be really specific about what you want :D               
                                                                         
here's an example of IF...THEN, using the very naughty GOTO statement :O 
                                                                         
                                                                         
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decision making                                                          
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x=0                                                                      
alabel:                                                                  
x=x+1                                             ______________________ 
IF x > 5 THEN ? x          ' > means "more than"  __6___________________ 
IF x < 10 THEN GOTO alabel ' < means "less than"  __7___________________ 
                                                  __8___________________ 
which will PRINT this, on the screen     ->       __9___________________ 
                                                  __10__________________ 
unless x is more than 5, it won't PRINT, and      ______________________ 
when x is 10, it won't go back to alabel.                                
                                                                         
                                                                         
                                                                         
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decision making                                                          
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i'm still using GOTO in these examples, because GOTO is easy to teach.   
sometimes, when it's easier to teach, it's easier to learn... but        
regardless, you will soon learn a couple statements that help to         
eliminate the use of GOTO, and are perfect for the example i just showed 
you. in fact, for what i just showed you, there are TWO perfectly        
acceptable command pairs that can be used just as easily.                
                                                                         
for now, here's another example:                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
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decision making                                                          
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PRINT "what's your name? - "                    ' *i'm not a chauvinist! 
LINE INPUT q$: q$=LTRIM$(RTRIM$(q$)) 'trim spaces                        
'standard reply                                                          
jim$ = "I am James T. Kirk... (Captain... of) "                          
jim$ = jim$ + "the Starship... Enterprise..."                            
                                                                         
?:? "are you a female alien? (y/n)"                                      
IF LCASE$(q$)=jim$ AND LCASE$(INPUT$(1))="y" THEN GOTO swoonfornoreason  
                                                                         
you see? it doesn't take much to make a program that thinks just like a  
female alien, especially one from the 1960's! (I Said "ALIEN!")*         
                                                                         
                                                                         
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decision making                                                          
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that example uses AND, let's try one that uses OR, and throw in ELSE...  
PRINT "what's your name? - "                                             
LINE INPUT q$: q$=LTRIM$(RTRIM$(q$)) 'trim spaces                        
o$=LCASE$(q$)                                                            
                                                                         
IF INSTR(o$,"bones")>0 OR INSTR(o$,"mccoy")>0 THEN                       
? "i need mr. sulu in sickbay, he thinks we";                            
? " really need a pilot to fly this thing!"                              
ELSE                                                                     
? "damnit, " + q$ +", you're not a doctor!"                              
END IF                                                                   
                                                                         
                                                                         
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decision making                                                          
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that's an IF... THEN block. if you really want, it works as one long     
line that won't fit the screen:                                          
                                                                         
IF INSTR(o$,"bones")>0 OR INSTR(o$,"mccoy")>0 THEN ? "i need mr. sulu    
in sickbay, he thinks we";: ? " actually need a pilot to fly this        
thing!" ELSE ? "damnit, " + q$ +", you're not a doctor!"                 
                                                                         
but for that to work you have to actually put it all on the same line.   
who would want to? hence, an IF... THEN block is used.                   
                                                                         
here's a way to check many conditions, using SELECT... CASE:             
                                                                         
                                                                         
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decision making                                                          
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? "input a number "; : LINE INPUT q$                                     
SELECT CASE VAL(q$)                                                      
CASE 1 TO 5: ? "your number is one at least, and five at most."          
CASE 6 TO 10                                                             
? "your number is six at least, and ten at most."                        
CASE IS = 15                                                             
? "fifteen? what's that got to do with anything?"                        
CASE IS > 20                                                             
? "more than 20? i quit!" ' no particular reason...                      
CASE ELSE: ? "i don't even understand this answer."                      
END SELECT                                                               
                                                                         
                                                                         
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decision making                                                          
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"CASE ELSE" of course, runs the code following that line if none of the  
other "CASE" conditions are met. CASE is also really handy for an if     
that uses numerous values:                                               
                                                                         
SELECT CASE LTRIM$(RTRIM$(LCASE$(q$)))                                   
CASE "susie", "janie", "jamie", "josie", "connie", "carrie", "mary"      
? "didn't we used to date?"                                              
CASE ELSE                                                                
? "so what are you doing tuesday?" '* AM NOT! SEE PAGE 5!                
END SELECT                                                               
                        -= end of chapter 11 =-                          
                                                                         
                                                                         
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an intro to puppybasic                                      (chapter 11) 
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