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Numbers

Dyalog APL supports both real numbers and complex numbers.

Real Numbers

Numbers are entered or displayed using conventional decimal notation (for example, 299792.458) or using a scaled form for example, 2.999792458E5).

On entry, a decimal point is optional if there is no fractional part. On output, a number with no fractional part (an integer) is displayed without a decimal point.

The scaled form consists of:

  1. an integer or decimal number called the mantissa,
  2. the letter E or e,
  3. an integer called the scale, or exponent.

The scale specifies the power of 10 by which the mantissa is to be multiplied.

Example

      12 23.24 23.0 2.145E2
12 23.24 23 214.5

Negative numbers are preceded by the high minus (¯) symbol, not to be confused with the minus (-) function. In scaled form, both the mantissa and the scale may be negative.

Example

      ¯22 2.145E¯2 ¯10.25
¯22 0.02145 ¯10.25

Complex Numbers

Complex numbers use the J notation introduced in IBM APL2 and are written as aJb or ajb (without spaces) where the real and imaginary parts a and b are written as described above. The capital J is always used to display a value.

Examples

      2+¯1*.5
2J1
      .3j.5
0.3J0.5
    1.2E5J¯4E¯4
120000J¯0.0004

Zilde

The empty vector (⍳0) may be represented by the numeric constant ⍬ called ZILDE.