01_02_constants.slide

# Constants

## constants
- cannot be changed
- created at compile time
- can only be numbers, characters (runes), strings or booleans
- can be initialized with a literal or a expression
- if expression is used to initialize, it must be constant expressions, evaluatable by the compiler

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## declaring constants
**syntax:**

    const constantName datatype = value

.play -numbers _concepts/01_introduction/02constants/1-different-type-declaration.go /START OMIT/,/END OMIT/

## declaring constants
**multiple constants in same line**

.play -numbers _concepts/01_introduction/02constants/2-multiple-consts1.go /START OMIT/,/END OMIT/

: Note: this way of coding doesn't work for constants of different data types

## declaring constants
**multiple constants in group**

.play -numbers _concepts/01_introduction/02constants/2-multiple-consts2.go /START OMIT/,/END OMIT/

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## enum: enumeration

## enum
**non enum example**

.play -numbers _concepts/01_introduction/02constants/3-enum0.go /START OMIT/,/END OMIT/


## enum
**manual enumeration**

.play -numbers _concepts/01_introduction/02constants/3-enum1.go /START OMIT/,/END OMIT/

## enum
**iota enumerator**
- integer type
- starts at 0 by default

.play -numbers _concepts/01_introduction/02constants/3-enum2a.go /START OMIT/,/END OMIT/


## enum
**iota enumerator**\
to start at a different number

.play -numbers _concepts/01_introduction/02constants/3-enum3.go /START OMIT/,/END OMIT/

## enum
**iota enumerator**\
to skip a part of the sequence 

.play -numbers _concepts/01_introduction/02constants/3-enum4.go /START OMIT/,/END OMIT/

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## constants at package level

.play -numbers _concepts/01_introduction/02constants/4-package-level.go /START OMIT/,/END OMIT/