boolean -- r7rs Type

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Super-types

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• (none);

Sub-types

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• true;
• false;

Referent definitions as input

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• boolean?;
• boolean=?;

Referent definitions as output

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• eq?;
• eqv?;
• equal?;
• boolean=?;
• symbol=?;
• =;
• <;
• >;
• <=;
• >=;
• string=?;
• string<?;
• string>?;
• string<=?;
• string>=?;
• string-ci=?;
• string-ci<?;
• string-ci>?;
• string-ci<=?;
• string-ci>=?;
• u8-ready?;
• char-ready?;
• file-exists?;
• char=?;
• char<?;
• char>?;
• char<=?;
• char>=?;
• char-ci=?;
• char-ci<?;
• char-ci>?;
• char-ci<=?;
• char-ci>=?;
• read-error?;
• file-error?;
• equivalent-by-identity?;
• equivalent-by-value-strict?;
• equivalent-by-value-strict-recursive?;

Referent definitions as output (recursive)

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• boolean?;
• not;
• symbol?;
• number?;
• integer?;
• real?;
• rational?;
• complex?;
• exact?;
• inexact?;
• exact-integer?;
• zero?;
• positive?;
• negative?;
• odd?;
• even?;
• finite?;
• infinite?;
• nan?;
• pair?;
• null?;
• list?;
• vector?;
• string?;
• bytevector?;
• port?;
• binary-port?;
• textual-port?;
• input-port?;
• input-port-open?;
• output-port?;
• output-port-open?;
• eof-object?;
• char?;
• char-alphabetic?;
• char-upper-case?;
• char-lower-case?;
• char-numeric?;
• char-whitespace?;
• procedure?;
• error-object?;
• promise?;
• proper-or-empty-list?;
• member;
• memq;
• memv;
• assoc;
• assq;
• assv;
• string->number;
• digit-value;

Note: These definitions produce an output that is a sub-type.

Predicate

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boolean?

Description

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The standard boolean objects for true and false are written as #t and #f. Alternatively, they can be written #true and #false, respectively. What really matters, though, are the objects that the Scheme conditional expressions (if, cond, and, or, when, unless, do) treat as true or false. The phrase a true value (or sometimes just true) means any object treated as true by the conditional expressions, and the phrase a false value (or false) means any object treated as false by the conditional expressions.

Of all the Scheme values, only #f counts as false in conditional expressions. All other Scheme values, including #t, count as true.

Note: Unlike some other dialects of Lisp, Scheme distinguishes #f and the empty list empty list from each other and from the symbol nil.

Boolean constants evaluate to themselves, so they do not need to be quoted in programs.

#t        ===>  #t
#f        ===>  #f
'#f       ===>  #f

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The text herein was sourced and adapted as described in the "R7RS attribution of various text snippets" appendix.

Categories

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• types-disjoint;

Categories recursive

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• types;