When to use comparisons
Fast recall
Quick revision
Core answer
slices.Equal, maps.Equal, or a domain-specific comparison when collection contents define equality. == is concise and compile-time checked for comparable types. An explicit helper is required for slices and maps and is often clearer when equality ignores fields, tolerates floating-point error, or follows business rules.Give a selection rule for comparisons, show a practical example, and explain when an explicit equality helper is clearer.
Saying “it depends” without naming the condition that changes the choice.
State the default choice and the specific reason to move away from it.
Interview-ready guide
Interview answer
Use built-in equality for comparable values and named structs whose comparable fields express value identity. Use
slices.Equal,maps.Equal, or a domain-specific comparison when collection contents define equality. Choose it because the behaviour is part of the requirement, not simply because the syntax is available.For example: arrays compare element by element because their type and length are fixed. Slices require an explicit helper such as
slices.Equalbecause a slice is a descriptor over backing storage. This small case shows the reason for the choice directly.==is concise and compile-time checked for comparable types. An explicit helper is required for slices and maps and is often clearer when equality ignores fields, tolerates floating-point error, or follows business rules. The two choices solve related problems but communicate different guarantees.Use built-in equality for comparable values and named structs whose comparable fields express value identity. Use
slices.Equal,maps.Equal, or a domain-specific comparison when collection contents define equality. Otherwise, use an explicit equality helper when it keeps the code simpler.
When to use comparisons
Direct Answer
Use built-in equality for comparable values and named structs whose comparable fields express value identity. Use slices.Equal, maps.Equal, or a domain-specific comparison when collection contents define equality. == is concise and compile-time checked for comparable types. An explicit helper is required for slices and maps and is often clearer when equality ignores fields, tolerates floating-point error, or follows business rules.
Deep Dive & Architecture
Go uses == and != for equality and <, <=, >, and >= for ordered values.
Booleans, numbers, strings, pointers, and channels are comparable; arrays and structs are comparable only when every element or field is comparable.
Use built-in equality for comparable values and named structs whose comparable fields express value identity. Use slices.Equal, maps.Equal, or a domain-specific comparison when collection contents define equality. == is concise and compile-time checked for comparable types. An explicit helper is required for slices and maps and is often clearer when equality ignores fields, tolerates floating-point error, or follows business rules.
A common mistake is comparing values without checking the type's comparison rules. Comparing two interfaces whose dynamic value is a slice or map causes a runtime panic. Know whether the static and dynamic types are comparable, use standard collection helpers, and define equality around the business meaning instead of forcing every type through ==.
Code Example
a := [2]int{1, 2}
b := [2]int{1, 2}
fmt.Println(a == b) // true
left := []int{1, 2}
right := []int{1, 2}
fmt.Println(slices.Equal(left, right))
Common Mistakes & Pitfalls
Saying “it depends” without naming the condition that changes the choice.
Check your understanding
Answer these without looking back at the article.
- What are comparisons in Go, and how do they work?
- How do comparisons compare with an explicit equality helper in Go?
- What common mistakes should you avoid with comparisons in Go?
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Every module on this page is also part of the full Java backend interview track.