Type this line of code into the Interactions Area and hit "Enter":
(triangle 50 "solid" "red")
1 What is the name of this function?
2 What did the expression evaluate to?
3 How many arguments does triangle expect?
4 What data type does the triangle function produce?
Catching Bugs
5 (triangle 20 "solid")
triangle: expects 3 arguments, but given 2: 20 solid at: line 1, column 0, in <interactions>
Can you spot the mistake?
6 (triangle "solid" "red" 20)
triangle: expects a non-negative number as 1st argument, but given: solid; other arguments were: red 20 at: line 1, column 0, in <interactions>
Can you spot the mistake?
7 (triangle 20 40 "solid" "red")
triangle: expects 3 arguments, but given 4: 20 40 solid red at: line 1, column 0, in <interactions>
Can you spot the mistake?
8 (triangle 20 solid "red")
solid: this variable is not defined at: line 1, column 0, in <interactions>
Can you spot the mistake?
9 (triangle 20 "striped" "red")
triangle: expects a style ("solid" / "outline") or an opacity value [0-255]) as 2nd argument, but given: "striped"; other arguments were: 20 "red" at: line 1, column 0, in <interactions>
Can you spot the mistake?
These materials were developed partly through support of the National Science Foundation,
(awards 1042210, 1535276, 1648684, and 1738598). 
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