Try and predict the result of each of the following pieces of Logo. Try each in the Logo interpreter to check your answer. Do all of the lines in order. Make sure you understand why Logo behaves the way it does in each example!
print sum 2 3 4 5
print (sum 2 3 4 5)
pr first first bf [yellow submarine]
show map "first [paperback writer]
show map [word first ? last ?] [lucy in the sky with diamonds]
repeat 5 [print [this boy]]
;Note the ~ symbols!
print ifelse 4=1+2 ~
["flying] ~
[[all you need is love]]
to pr2nd :thing
print first bf :thing
end
pr2nd [the 1 after 909]
print first pr2nd [hey jude]
to greet :person
say [how are you,]
end
to say :saying
print sentence :saying :person
end
greet "ringo
to who :sent
foreach [pete roger john keith] "describe
end
to describe :person
print se :person :sent
end
who [sells out]
make "bass "paul
print :bass
make :bass "bass
print :paul
Write the procedure countdown in Logo which takes a number and prints on separate lines a countdown followed by the line "blastoff!" as shown below:
? countdown 5 5 4 3 2 1 blastoff!
Write the procedure downup which behaves in the following way:
? downup "pacman pacman pacma pacm pac pa p pa pac pacm pacma pacman ? downup [foo bar baz garply] [foo bar baz garply] [foo bar baz] [foo bar] [foo] [foo bar] [foo bar baz] [foo bar baz garply]
Hint: There's a procedure in Logo called butlast (or bl for short) which takes either a word and returns the word without the last letter or a sentence and returns a sentence with all but the last item. Also, emptyp works for both sentences and words!
Write the procedure double_evens which takes a sentence of numbers and outputs the same sentence with the all of the even values doubled. Here's an example of how it should work:
? show double_evens [4 0 5 2 1] [8 0 5 4 1]
Write the procedure repeated which takes the name of a procedure :fn, a number :n, and an value :arg and outputs the result of applying :fn to :arg :n times. An example of how it should work is shown below:
? print repeated "butlast 3 "downstream downstr ? print repeated "butfirst 4 "downstream stream
Hint: you'll probably want to use the procedure run