Logo Lesson 5 TBE 540 40 Fall 2004 Farah Fisher Prerequisites Given a shape use basic Logo commands and or a procedure to draw the shape with and without the use of variables Use SAVE LOAD and POTS to manage Logo workspaces Demonstrate the use of RANDOM Objectives Put a list of words into a variable and print any item of the list Print a sentence in Logo with and without variables Print a sentence in Logo from randomly chosen words Demonstrate use of IF and IFELSE Create a Logo procedure that demonstrates the use of recursion Logo Lists A list in Logo a set of values all stored under the same variable name Other programming languages call this an array Each value stored in the list is called an item Each item has a number e g in the list HOT COLD DOG item 3 is DOG Logo Lists Here is a sample of the creation of a list within a procedure MAKE COLORS RED GREEN BLUE If you print PR COLORS all three colors will appear If you PR ITEM 2 COLORS the word GREEN will appear Logo Lists PR ITEM 1 RANDOM 3 COLORS will display a randomly chosen word from the list of three Lists are very useful in choosing words at random MAKE WORD1 ITEM 1 RANDOM 3 COLORS would put a randomly chosen word from the list into the variable WORD1 Logo Lists Logo lists may also contain numbers Here is a list of prime numbers put into a variable called PRIME MAKE PRIME 1 2 3 5 7 11 13 17 19 23 What would appear if you typed this PR ITEM 6 PRIME 11 would be printed since it is the 6th item How would you choose at random from the list A possible command MAKE F ITEM 1 RANDOM 10 PRIME Sentences in Logo You have seen several examples of the PR print command It can be used to display the value of variables or messages Next you will see how to put several pieces of information together in a sentence Sentences in Logo If you already know all the words in a sentence you can simply put it inside brackets like PR HERE IT IS But what if you are trying to include variables words or numbers For example suppose you asked someone to enter his her name and you want to print HI and the name he she entered Sentences in Logo The commands to ask for and get the name would be PR PLEASE TYPE YOUR NAME MAKE NM READLIST If you typed PR HI NM to print you would not get the result you want PR HI NM would actually display HI NM rather than the actual name since information in is taken literally Sentences in Logo Take a look at the third line of commands PR PLEASE TYPE YOUR NAME MAKE NM READLIST PR SE HI NM The SE means SENTENCE print as a sentence with spaces between the parts Notice the use of instead of The HI is taken literally but the NM prints whatever is input in the previous line Sentences in Logo Examine the following procedure TO EXCHANGE PR PLEASE TYPE YOUR NAME MAKE NM READLIST PR SE HI NM END Running the procedure EXCHANGE to start the procedure PLEASE TYPE YOUR NAME MARY SMITH entered by the user HI MARY SMITH Sentences in Logo Next we are going to create a procedure that puts together sentences from randomly chosen words This procedure will 1 create lists of words verbs nouns adjectives 2 choose randomly from these lists and 3 put the randomly chosen words into a sentence and print it Sentences in Logo We will use a sentence format like this THE adjective noun verb Example THE HAPPY DOG RUNS To make lists of words MAKE VERBS RUNS HOPS SINGS MAKE NOUNS DOG TREE CAR MAKE ADJ HAPPY GREEN BIG Sentences in Logo To choose randomly from these lists MAKE WORD1 ITEM 1 RANDOM 3 ADJ MAKE WORD2 ITEM 1 RANDOM 3 NOUNS MAKE WORD3 ITEM 1 RANDOM 3 VERBS Sentences in Logo The procedure thus far TO RANDOM SENTENCE MAKE VERBS RUNS HOPS SINGS MAKE NOUNS DOG TREE CAR MAKE ADJ HAPPY GREEN BIG MAKE WORD1 ITEM 1 RANDOM 3 ADJ MAKE WORD2 ITEM 1 RANDOM 3 NOUNS MAKE WORD3 ITEM 1 RANDOM 3 VERBS Sentences in Logo To put the words into a sentence we will use PR print and SE sentence Remember that we are trying for THE adjective noun verb Here is the Logo printing command we will use PR SE THE WORD1 WORD2 WORD3 Sentences in Logo The final version TO RANDOM SENTENCE MAKE VERBS RUNS HOPS SINGS MAKE NOUNS DOG TREE CAR MAKE ADJ HAPPY GREEN BIG MAKE WORD1 ITEM 1 RANDOM 3 ADJ MAKE WORD2 ITEM 1 RANDOM 3 NOUNS MAKE WORD3 ITEM 1 RANDOM 3 VERBS PR SE THE WORD1 WORD2 WORD3 END Sentences in Logo How could you make RANDOM SENTENCE into a random story How about TO RANDOM STORY REPEAT 5 RANDOM SENTENCE END An Addition Drill Logo sentences can be constructed using numbers too Suppose you are trying to make an addition drill with random problems You would have to create a procedure that 1 chooses two random numbers 2 displays the addition problem 3 gets the answer 4 checks to see if it is correct and 5 gives feedback An Addition Drill Choosing two random numbers would look like this MAKE X 1 RANDOM 10 MAKE Y 1 RANDOM 10 To print the problem as a sentence PR SE X Y What would be different for a multiplication problem For larger numbers An Addition Drill Getting the answer would look like this MAKE ANS FIRST READLIST The procedure so far is TO ADD PROBLEM MAKE X 1 RANDOM 10 MAKE Y 1 RANDOM 10 PR SE X Y MAKE ANS FIRST READLIST An Addition Drill The next step is to check the answer The question is how will the computer know the right answer when two random numbers were chosen The correct answer should be X Y since X and Y contain the chosen numbers But how will the computer compare the student s answer with the correct answer An Addition Drill The IF command is part of all programming languages It asks the computer to make a judgment about whether something is true or false In this case the student s answer will either be the same as the computer s or not the same the equality will either be true equal or false not equal An Addition Drill The IF statement also has to tell Logo what to do if the judgment is true In this case we will tell Logo to print the word RIGHT if the student s answer is the same as the computer s Here is the command IF ANS X Y PR RIGHT An explanation follows on the next slide An Addition Drill IF ANS X Y PR RIGHT ANS contains the student s answer X Y is the correct answer If the two are the same equality is true then whatever is …