Reference · Math

math.frexp

math.frexp(num) -> list

What it does

A number taken apart into a mantissa and an exponent of two, as a list [m, e] with x == m * 2^e and 0.5 <= |m| < 1, as Python's math.frexp. m is a float and e an int. math.frexp(8) is [0.5, 4]. math.ldexp puts the two back together.

Examples

print(math.frexp(8), math.frexp(0.75), math.frexp(-5), math.frexp(0.1))let [m, e] = math.frexp(10)print(m, e, math.ldexp(m, e))

[0.5, 4] [0.75, 0] [-0.625, 3] [0.8, -3]0.625 4 10.0

Edge cases

• Zero gives [0.0, 0], and -0.0 gives [-0.0, 0].
• The mantissa keeps the number's sign; the exponent is the number's size in bits, so math.frexp(1) is [0.5, 1] and math.frexp(3) is [0.75, 2].
• Infinity and NaN come back as the mantissa with an exponent of 0; neither is an error.
• The largest float has an exponent of 1024.

print(math.frexp(0), math.frexp(-0.0), math.frexp(1), math.frexp(3))print(math.frexp(float("inf")), math.frexp(float("nan")), math.frexp(1e308))

[0.0, 0] [-0.0, 0] [0.5, 1] [0.75, 2][inf, 0] [NaN, 0] [0.5562684646268004, 1024]

Errors

An argument that is not a number is a runtime error, not an error value.

print(math.frexp(null))

line 1: `math.frexp` expects a number as argument 1, got null

Chaining

In a pipeline the number comes first. The exponent alone is the order of magnitude in powers of two:

print(1024 | math.frexp | last)print([1, 2, 4, 1000] | map((x) => math.frexp(x) | last))

11[1, 2, 3, 10]

See also

math.ldexp, math.modf, math.log

Edit this page on GitHub · every example's output was made by running it (tools/refcheck.mjs) · questions on Discord or r/quillo