Fundamentals of CS I (CS151 2001S) : Reference
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Predicate  rational? 

Parameters  n, a number 
Purpose  Determines if v is a rational number (expressible as a ratio of two integers). 
Produces  A truth value: true (#t )
if n is a rational number,
false (#f ) if it's not a rational number.

Preconditions  Only one parameter (verified). 
Postconditions  Returns true if and only if the parameter is a rational number. Note that my version of Scheme seems to treat any noncomplex 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 
"..." (double quote)

+ (plus)

#\character (pound backslash)

#\newline

#\space

; (semicolon)
* (times)

abs

and

append

boolean?

car

cdr

char?

char<?

char<=?

char=?

char>=?

char>?

charalphabetic?

charci<?

charci<=?

charci=?

charci>?

charci>=?

char>integer

chardowncase

charlowercase?

charnumeric?

charuppercase?

charupcase

charwhitespace?

complex?

cons

eq?

equal?

eqv?

exact?

exact>inexact

exp

expt

inexact?

integer?

integer>char
length

list

list?

listref

null

null?

number?

procedure?
rational?

real?

reverse
sqrt

string?

symbol?
[Current]
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[Outlines]
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Sets
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[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 22:41:19 2001.