► |  | Teachpacks

1 | Ht DP Teachpacks
2 | Ht DP/ 2e Teachpacks

▼ | 1 | Ht DP Teachpacks

1.1 | Manipulating Images: "image.ss"
1.2 | Simulations and Animations: "world.ss"
1.3 | Converting Temperatures: "convert.ss"
1.4 | Guessing Numbers: "guess.ss"
1.5 | Master Minding: "master.ss"
1.6 | Simple Drawing: "draw.ss"
1.7 | Hangman: "hangman.ss"
1.8 | Managing Control Arrows: "arrow.ss"
1.9 | Manipulating Simple HTML Documents: "docs.ss"
1.10 | Working with Files and Directories: "dir.ss"
1.11 | Graphing Functions: "graphing.ss"
1.12 | Simple Graphical User Interfaces: "gui.ss"
1.13 | An Arrow GUI: "arrow-gui.ss"
1.14 | Controlling an Elevator: "elevator.ss"
1.15 | Queens: "show-queen.ss"
1.16 | Matrix Operations: "matrix.ss"

On this page:

convert-gui
convert-repl
convert-file

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#### 1.3`` Converting Temperatures: "convert.ss"

The teachpack convert.ss provides three functions for converting Fahrenheit temperatures to Celsius. It is useful for a single exercise in HtDP. Its purpose is to demonstrate the independence of “form” (user interface) and “function” (also known as “model”).

( convert-gui convert) → true
convert : ( -> number? number? )

Consumes a conversion function from Fahrenheit to Celsius and creates a graphical user interface with two rulers, which users can use to convert temperatures according to the given temperature conversion function.

( convert-repl convert) → true
convert : ( -> number? number? )

Consumes a conversion function from Fahrenheit to Celsius and then starts a read-evaluate-print loop. The loop prompts users to enter a number and then converts the number according to the given temperature conversion function. A user can exit the loop by entering “x.”

( convert-file in convert out) → true
in : string?
convert : ( -> number? number? )
out : string?

Consumes a file name in, a conversion function from Fahrenheit to Celsius, and a string out. The program then reads all the number from in, converts them according to convert, and prints the results to the newly created file out.

Warning: If out already exists, it is deleted.

Example: Create a file with name "in.dat" with some numbers in it, using your favorite text editor on your computer. Define a function f2c in the Definitions window and set teachpack to “convert.ss” and click RUN. Then evaluate

( convert-gui f2c)
; and
( convert-file "in.dat" f2c "out.dat")
; and
( convert-repl f2c)

Finally inspect the file "out.dat" and use the repl to check the answers.
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