The Grinnell Scheme Web: The / procedure

What about division, then? How do I divide one number by another in Scheme?

Call the / procedure, giving it the dividend as the first operand and the divisor as the second:

> (/ 76 19)
4
> (/ -300 25)
-12
> (/ 82 34)
2.4117647058824

If the operands are both integers and the division comes out even, Scheme returns an integer. If it doesn't come out even, the kind of number returned varies from one implementation to another. For example, SCM (which does not support rationals) returns a real approximation to the quotient, as shown above, while Scheme 48 returns a rational:

> (/ 82 34)
41/17

The rare implementation that supports only integers is not required to provide the / procedure at all.

Does / accept operands that are not integers?

Yes. It accepts numbers of any kind that is supported by the implementation:

> (/ 3/4 1/12)
9
> (/ 7.2+6.1i -4.3i)
-1.4186046511628+1.6744186046512i

What will the / procedure do if you give it a different number of operands?

If you give it just one operand, it returns the reciprocal (the multiplicative inverse) of the operand:

> (/ 5)
1/5
> (/ 21/5)
5/21
> (/ -2i)
0+1/2i

Giving it no operands at all is an error, just as in the case of the - procedure.

The Scheme standard does not require an implementation of the / procedure to make any provision for more than two operands. Some Scheme implementations (SCM and Elk, for instance) treat any extra operands as additional divisors:

> (/ 2520 3 5 7)
24

Others consider such calls erroneous:

> (/ 2520 3 5 7)

Error: wrong number of arguments
       (/ 2520 3 5 7)

The careful programmer will avoid giving / more than two operands.

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http://www.math.grin.edu/~stone/scheme-web/slash.html

created June 23, 1995
last revised December 30, 1995