04Variables
Constants
Values that never change, declared with ကိန်းသေ.
Some values never change while a program runs: the number π, the length of a week, the
pass mark of a test. Declare these as constants with ကိန်းသေ ("fixed
number") instead of ကိန်းရှင် ("living number", a variable).
စံကား
Expected output
၃.၁၄၁၅၉
၁၄
| Zaka | Reads as | Makes |
|---|---|---|
ကိန်းရှင် | "living number" | a variable: its value can change |
ကိန်းသေ | "fixed number" | a constant: its value never changes |
Constants make a program simpler to read (တစ်ပတ် is clearer than ၇) and simpler to
change: fix the value in one place and each use follows.
Rules for constants
A constant must be given its value when it is declared:
စံကားZK0308
Expected error
error[ZK0308]: constant "တစ်ပတ်" needs an initial value
After that, it can never be given a new value. The next page shows how to change a variable; attempting the same on a constant fails:
စံကားZK0306
Expected error
error[ZK0306]: "တစ်ပတ်" is a constant and cannot be assigned
Hands on
- Declare a constant for the number of minutes in an hour, and use it to print the number of minutes in 24 hours.
Next: Changing a variable.