26 lines
739 B
Racket
26 lines
739 B
Racket
#reader(lib "docreader.ss" "scribble")
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@require[(lib "manual.ss" "scribble")]
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@require[(lib "eval.ss" "scribble")]
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@require["guide-utils.ss"]
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@title[#:tag "guide:booleans"]{Booleans}
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Scheme has two distinguished constants to represent boolean values:
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@scheme[#t] for true and @scheme[#f] for false. Uppercase
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@schemevalfont{#T} and @schemevalfont{#F} are parsed as the same
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values, but the lowercase forms are preferred.
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The @scheme[boolean?] procedure recognizes the two boolean
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constants. In the result of a test expression for @scheme[if],
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@scheme[cond], @scheme[and], @scheme[or], etc., however, any value
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other than @scheme[#f] counts as true.
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@examples[
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(= 2 (+ 1 1))
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(boolean? #t)
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(boolean? #f)
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(boolean? "no")
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(if "no" 1 0)
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]
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