51 lines
2.0 KiB
Racket
51 lines
2.0 KiB
Racket
#lang scribble/doc
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@(require scribble/manual "shared.rkt"
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(for-label racket teachpack/htdp/convert))
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@teachpack["convert"]{Converting Temperatures}
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@;declare-exporting[teachpack/htdp/convert]
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@defmodule[#:require-form beginner-require htdp/convert]
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The teachpack @racket[convert.rkt] provides three functions for
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converting Fahrenheit temperatures to Celsius. It is useful for a single
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exercise in HtDP. Its purpose is to demonstrate the independence of
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``form'' (user interface) and ``function'' (also known as ``model'').
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@defproc[(convert-gui [convert (-> number? number?)]) true]{Consumes a
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conversion function from Fahrenheit to Celsius and creates a graphical user
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interface with two rulers, which users can use to convert temperatures
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according to the given temperature conversion function.}
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@defproc[(convert-repl [convert (-> number? number?)]) true]{Consumes a
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conversion function from Fahrenheit to Celsius and then starts a
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read-evaluate-print loop. The loop prompts users to enter a number and then
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converts the number according to the given temperature conversion function.
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A user can exit the loop by entering ``x.''}
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@defproc[(convert-file [in string?][convert (-> number? number?)][out string?]) true]{Consumes a
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file name @racket[in], a
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conversion function from Fahrenheit to Celsius, and a string
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@racket[out]. The program then reads all the number from
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@racket[in], converts them according to @racket[convert], and prints the
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results to the newly created file @racket[out].
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@bold{Warning}: If @racket[out] already exists, it is deleted.}
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Example: Create a file with name @racket["in.dat"] with some numbers in
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it, using your favorite text editor on your computer. Define a function
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@racket[f2c] in the Definitions window and set teachpack to
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@filepath{convert.rkt} and click Run. Then evaluate
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@(begin
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#reader scribble/comment-reader
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(racketblock
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(convert-gui f2c)
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;; and
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(convert-file "in.dat" f2c "out.dat")
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;; and
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(convert-repl f2c)
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))
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Finally inspect the file @racket["out.dat"] and use the repl to check the
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answers.
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