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Floating-point numbers
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Floating-point numbers in Go

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About Floating-point numbers

A floating-point number is a number with zero or more digits behind the decimal separator. Examples are -2.4, 0.1, 3.14, 16.984025 and 1024.0.

Different floating-point types can store different numbers of digits after the digit separator - this is referred to as its precision.

Go has two floating-point types:

  • float32: 32 bits (~6-9 digits precision).
  • float64: 64 bits (~15-17 digits precision). This is the default floating-point type.

As can be seen, both types can store a different number of digits. This means that trying to store PI in a float32 will only store the first 6 to 9 digits (with the last digit being rounded).

By default, Go will use float64 for floating-point numbers, unless the floating-point number is:

  1. assigned to a variable with type float32, or
  2. returned from a function with return type float32, or
  3. passed as an argument to the float32() function.

Always be careful when checking the values of floating-point types for equality, as values that can appear to represent the same value could actually be different.

You can find a short introduction to floating-point numbers at 0.30000000000000004.com. The Float Toy page has a nice, graphical explanation how a floating-point numbers' bits are converted to an actual floating-point value.

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Learn Floating-point numbers