Math operations

Math operations

The math operations of Arc are fairly limited. Many expected operations, such as trigonometry, are missing.

* args
Multiplication.
>(* 2 3)
6
+ args
Addition. This operator also performs string and list concatenation.
>(+ 1 2 3)
6
>(+ "ab" "c" "de")
"abcde"
>(+ '(1 2) '(3 4) '(5))
(1 2 3 4 5)
- args
Subtraction.
>(- 3 2)
1
/ args
Division
>(/ 1 2)
1/2
>(/ 1.0 2)
0.5
cos arg
Cosine function. New in arc3.
>(cos 3.14)
-0.9999987317275395
expt base exponent
Exponentiation.
>(expt 2 3)
8
log arg
Natuarl logarithm function. New in arc3.
>(log 100)
4.605170185988092
mod dividend divisor
>(mod 10 3)
1
>(mod -10 3)
2
rand [max]
Returns a random number between 0 and 1, or between 0 and the specified integer (excluding the integer).
>(rand 10)
6
>(rand)
0.48564099194792254
sin arg
Sine function. New in arc3.
>(sin 3.14)
0.0015926529164868282
sqrt number
Square root operation
>(sqrt 2)
1.4142135623730951
>(sqrt -1)
0+1i
tan arg
Tangent function. New in arc3.
>(tan 3.14)
-0.001592654936407223
trunc number
Truncates to an integer. Was 'truncate' in arc0.
>(trunc 1.9)
1
>(trunc -1.1)
-1
number n
Tests if n is a number (int or num).
>(number 3.14)
t
positive x
Tests if x is a number and is positive (>= 0). This fails on complex numbers.
>(positive 0)
nil
>(positive -2)
nil
>(positive "a")
nil
abs n
Returns the absolute value.
>(abs -3)
3
round n
Rounds n to the nearest value. Halfs are rounded to the nearest even number.
>(round 1/2)
0
>(round 1.5)
2
>(round 0.4)
0
>(round -1.5)
-2
roundup n
Rounds n to the nearest value. Halfs are rounded away from zero.
>(roundup 1/2)
1
>(roundup 1.5)
2
>(roundup 0.4)
0
>(roundup -1.5)
-2
nearest n quantum
Rounds down to the nearest multiple of n. Renamed in arc3.
>(nearest 3.14 0.1)
3.1
>(nearest -5 10)
-10
median list
Returns the median of the list (the element at the midpoint of the list when sorted highest-to-lowest). Takes the earlier element for an even-length list.
>(median '(1 5 3 2 4))
3
>(median '("dog" "cat" "bird") (median '(1 2 3 4)))
Error:  median: arity mismatch;
 the expected number of argu
ments does not match the given number
  expected: 1
  given:
 2
  arguments...:
   '("dog" "cat" "bird" . nil)
   2

med list [compare-fn]
Returns the median of the list (the element at the midpoint of the list when sorted according to compare-fn). Takes the later element for an even-length list. New in arc3.
>(med '(1 5 3 2 4))
3
>(med '("dog" "cat" "bird") (med '(1 2 3 4)))
Error: Function call on inappropriate object 2 ("bird" "cat"
)

avg numbers
Computes the average of a list of numbers.
>(avg '(1+2i 0.4))
0.7+1.0i
even n
Tests if n is even. Argument n must be an integer.
>(even 1)
nil
>(even 2)
t
odd n
Tests if n is odd. Argument n must be an integer.
>(odd 1)
t
>(odd 2)
nil
max [arg ...]
Returns the maximum arg. The args must be comparable with >.
>(max 10 -3 5)
10
>(max "cat" "dog" "bird")
"dog"
min [arg ...]
Returns the minimum arg. The args must be comparable with <.
>(min 10 -3 5)
-3
>(min "cat" "dog" "bird")
"bird"
multiple x base
Tests if x is a multiple of base.
>(multiple 10 5)
t
>(multiple 11 5)
nil

Copyright 2008 Ken Shirriff.