Fundamentals of CS I (CS151 2001S) : Reference

rational?: determine whether a value is rational

Predicaterational?
Parametersn, a number
PurposeDetermines if v is a rational number (expressible as a ratio of two integers).
ProducesA truth value: true (#t) if n is a rational number, false (#f) if it's not a rational number.
PreconditionsOnly one parameter (verified).
PostconditionsReturns true if and only if the parameter is a rational number. Note that my version of Scheme seems to treat any non-complex numbers as rational (hmmmm). Note also that values that are not numbers (e.g., lists and symbols) are not rational.
Examples
> (rational? 1)
#t
> (rational? 3/2)
#t
> (rational? -1/2)
#t
> (rational? 1.3)
#t
> (rational? (sqrt 2))
#t
> (exp 1)
2.718281828459045
> (rational? (exp 1))
#t
> (rational? (sqrt -1))
#f
> (rational? 'a)
#f

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The source was last modified Wed Jan 31 22:41:19 2001.