constants are also variables that are assigned an initial value that can never change in the program’s life. euphoria allows to define constants using constant keyword as follows −

constant max = 100
constant upper = max - 10, lower = 5
constant name_list = {"fred", "george", "larry"}

the result of any expression can be assigned to a constant, even one involving calls to previously defined functions, but once the assignment is made, the value of the constant variable is "locked in".

constants may not be declared inside a subroutine. the scope of a constant that does not have a scope modifier, starts at the declaration and ends and the end of the file it is declared in.

examples

#!/home/euphoria-4.0b2/bin/eui

constant max = 100
constant upper = max - 10, lower = 5

printf(1, "value of max %d\n", max )
printf(1, "value of upper %d\n", upper )
printf(1, "value of lower %d\n", lower )

max = max + 1
printf(1, "value of max %d\n", max )

this produces the following error −

./test.ex:10
<0110>:: may not change the value of a constant
max = max + 1
   ^

press enter

if you delete last two lines from the example, then it produces the following result −

value of max 100
value of upper 90
value of lower 5

the enums

an enumerated value is a special type of constant where the first value defaults to the number 1 and each item after that is incremented by 1. enums can only take numeric values.

enums may not be declared inside a subroutine. the scope of an enum that does not have a scope modifier, starts at the declaration and ends and the end of the file it is declared in.

examples

#!/home/euphoria-4.0b2/bin/eui

enum one, two, three, four

printf(1, "value of one %d\n", one )
printf(1, "value of two %d\n", two )
printf(1, "value of three %d\n", three )
printf(1, "value of four %d\n", four )

this will produce following result −

value of one 1
value of two 2
value of three 3
value of four 4

you can change the value of any one item by assigning it a numeric value. subsequent values are always the previous value plus one, unless they too are assigned a default value.

#!/home/euphoria-4.0b2/bin/eui

enum one, two, three, abc=10, xyz

printf(1, "value of one %d\n", one )
printf(1, "value of two %d\n", two )
printf(1, "value of three %d\n", three )
printf(1, "value of abc %d\n", abc )
printf(1, "value of xyz %d\n", xyz )

this produce the following result −

value of one 1
value of two 2
value of three 3
value of abc 10
value of xyz 11

sequences use integer indices, but with enum you may write code like this −

enum x, y
sequence point = { 0,0 }

point[x] = 3
point[y] = 4