INF, Nan, Zero and IEEE/SANE arithmetic

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Analytica 4.0 complies with the IEEE 754 standard (and the related SANE standard) for floating point arithmetic, including in its treatment of infinite values. As specified by IEEE 754, Analytica represents three special values:

INF: Infinity

-INF: negative infinity

NaN: Not a Number

Analytica follows IEEE 754 and SANE standards in the following:

x * INF → INF for x>0

x * -INF → INF for x<0

INF - INF → NaN

x / 0 → INF for x>0

0 * INF → NaN

0 / 0 → NaN

x * NaN → NaN

Note: x>0 means x is not NaN but may be INF.

In this, Analytica 4.0 differs from 3.1 and earlier releases which did not comply with the IEEE 754 standard when multiplying INF or Nan by zero. Analytica 3.1 and earlier gave:

0 * INF → 0

0 * NaN → 0

If you find that your model built with Analytica 3.1 or earlier is now generating NaN, where before it generated numbers, this change could be the reason. Analytica 4.0 will give a warning if it detects such a multiplication of INF or NaN by zero, if you check Show Result Warnings in the Preferences dialog from the Edit menu. on.

You can test whether x is Nan or INF in these ways:

x=INF

x=-INF

IsNan(x) → True (1) if x=Nan

IsNumber(x) → True (1) if x is a number, INF, -INF, or Nan, and False (0) if x is a text, reference, Null, Undefined, or other type.