Magnitude
Magnitude (|
), or Absolute Value, is a monadic scalar function which gives the absolute value of a real or complex number. Magnitude shares the glyph <syntaxhighlight lang=apl inline>|</source> with the dyadic arithmetic function Residue.
Examples
<syntaxhighlight lang=apl>
|0 1 2 ¯1 ¯2
0 1 2 1 2
|0J2 ¯3J¯4
2 5 </source>
Properties
The magnitude of any number is a non-negative real number.
For real numbers, the magnitude equals the original number times (or divided by, for non-zero numbers) its sign.
<syntaxhighlight lang=apl>
v←0 1E¯100 20 1E300 ¯1E¯100 ¯20 ¯1E300 (|v)≡v××v
1
(|v)=v÷×v
0 1 1 1 1 1 1 </source>
For complex numbers, the magnitude is defined as the Euclidean distance from the number 0 on the complex plane.
<syntaxhighlight lang=apl>
Dist←{0.5*⍨+.×⍨9 11○⍵} ⍝ Square root of square sum of real and imaginary parts Dist¨ 0 1J2 ¯3J4
0 2.236067977 5
|0 1J2 ¯3J4
0 2.236067977 5
</source>
Any real or complex number is equal to the product of its signum and magnitude.
<syntaxhighlight lang=apl>
(⊢ ≡ ××|) 0 1 1E¯300 ¯2.5 0J3.5 ¯3J¯4
1
</source>