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Complex Numbers

Go has two built-in complex number types: complex64 and complex128. Both store a real and an imaginary part — they differ only in the precision of each part.

Declaring Complex Numbers​

Use the complex() built-in to construct a complex value from its real and imaginary parts:

var c64 complex64 = complex(1.5, 2.5) // float32 real and imaginary parts

c128 := complex(3.0, -4.0) // float64 parts — complex128 inferred by :=

Output:

complex64: (1.5+2.5i)  | type: complex64
complex128: (3-4i)     | type: complex128
TypePartsNotes
complex64two float32less precision, smaller memory footprint
complex128two float64default type inferred by :=

Extracting Real and Imaginary Parts​

real() and imag() return the individual parts of a complex value:

fmt.Printf("real(c128): %g\n", real(c128)) // 3
fmt.Printf("imag(c128): %g\n", imag(c128)) // -4

Arithmetic​

Standard arithmetic operators work directly on complex values:

sum := c128 + complex(1.0, 1.0)
fmt.Println("c128 + (1+1i):", sum) // (4-3i)

Key Takeaways​

  • Two types: complex64 (float32 parts) and complex128 (float64 parts) — := infers complex128
  • complex() built-in: constructs a complex number from real and imaginary parts
  • real() and imag(): extract the two parts from any complex value
  • Arithmetic works directly: +, -, *, / all operate on complex values without conversion
  • Floats — float64 is the underlying type of complex128 parts
  • Go Types — other built-in types