Fundamentals of CS I (CS151 2001S) : Reference

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real?: determine whether a value is real

Predicatereal?
Parametersn, a number
PurposeDetermines if v is a real number (no complex part).
ProducesA truth value: true (#t) if n is a real number, false (#f) if it's not a real number.
PreconditionsOnly one parameter (verified).
PostconditionsReturns true if and only if the parameter is a real number. Note that my version of Scheme seems to treat any non-complex numbers as real. Note also that values that are not numbers (e.g., lists and symbols) are not real.
Examples
> (real? 1)
#t
> (real? 3/2)
#t
> (real? -1/2)
#t
> (real? 1.3)
#t
> (real? (sqrt 2))
#t
> (exp 1)
2.718281828459045
> (real? (exp 1))
#t
> (real? (sqrt -1))
#f
> (real? 'a)
#f

"..." (double quote) | + (plus) | #\character (pound backslash) | #\newline | #\space | ; (semicolon) * (times) | abs | and | append | boolean? | car | cdr | char? | char<? | char<=? | char=? | char>=? | char>? | char-alphabetic? | char-ci<? | char-ci<=? | char-ci=? | char-ci>? | char-ci>=? | char->integer | char-downcase | char-lower-case? | char-numeric? | char-upper-case? | char-upcase | char-whitespace? | complex? | cons | eq? | equal? | eqv? | exact? | exact->inexact | exp | expt | inexact? | integer? | integer->char length | list | list? | list-ref | null | null? | number? | procedure? rational? | real? | reverse sqrt | string? | symbol?

[Current] [Discussions] [Glance] [Honesty] [Instructions] [Links] [News] [Search] [Syllabus] Primary
[Examples] [Exams] [Handouts] [Homework] [Labs] [Outlines] [Quizzes] [Readings] [Reference] Sets
[Blackboard] [Scheme Report] [SamR's Schedule] [Rebelsky/Fall 2000] [Walker/Fall2000] [Stone/Spring2000] Links

Disclaimer: I usually create these pages on the fly. This means that they are rarely proofread and may contain bad grammar and incorrect details. It also means that I may update them regularly (see the history for more details). Feel free to contact me with any suggestions for changes.

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The source was last modified Wed Jan 31 22:41:39 2001.