ldexp returns mantissa and exponent of input number in Python

ldexp() returns the mantissa and exponent of an input number.

ldexp(m,e) # output n

n : is the output number
m : is the mantissa , a floating point number
e : is the exponent , an integer

Relation between output number with Mantissa ( m ) and exponent ( e )

n == m * 2**e

Example

import math
print(math.ldexp(2,3))  # 16.0

With negative numbers

print(math.ldexp(-2,3)) # -16.0
print(math.ldexp(2,-3)) # 0.25

The second argument ( exponent ) has to be an integer, we can't use float.

print(math.ldexp(2.2,-3.3))

This will generate an TypeError

Understanding math.ldexp() and Related Functions

Use Case: Scientific Computing

math.ldexp() is useful in scenarios involving floating-point arithmetic, particularly in scientific computing and graphics, where low-level operations require manipulating the mantissa and exponent of a number.

Example: Comparison with frexp()

Using frexp() to decompose a number and ldexp() to reconstruct it:

import math
n = 16
m, e = math.frexp(n)  # (mantissa, exponent)
print(m, e)  # Outputs: 0.5, 5
print(math.ldexp(m, e))  # Outputs: 16.0

Binary-Decimal Conversion Example

mantissa = 0.75
exponent = 4
print(math.ldexp(mantissa, exponent))  # Outputs: 12.0

This is useful in binary-decimal conversions for precise floating-point calculations.

We can also use frexp() the inverse function of ldexp() to get Mantissa and exponent of n

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Subhendu Mohapatra

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