git @ Cat's Eye Technologies Robin / master stdlib / abs.robin
master

Tree @master (Download .tar.gz)

abs.robin @master — raw · history · blame 

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
;'<<SPEC'

<!--
Copyright (c) 2012-2024, Chris Pressey, Cat's Eye Technologies.
This file is distributed under a 2-clause BSD license.  See LICENSES/ dir.
SPDX-License-Identifier: LicenseRef-BSD-2-Clause-X-Robin
-->

### `abs` ###

    -> Tests for functionality "Evaluate Robin Expression (with Arith)"

`abs` evaluates its single argument to a number, and evaluates to
the absolute value of that number (where the sign is always positive.)

    |   (abs 5)
    = 5

    |   (abs (subtract 0 5))
    = 5

    |   (abs 0)
    = 0

`abs` expects exactly one numeric argument.

    |   (abs)
    ? abort (illegal-arguments

    |   (abs 14 23)
    ? abort (illegal-arguments

    |   (abs #t)
    ? abort (expected-number #t)

'<<SPEC'

(define abs (fun (a)
  (if (equal? (sign a) 1) a (subtract 0 a))))