Variables

Symbols in Idio and, by extension, variables can be fairly flexible compared to many languages. In particular, many punctuation characters are valid in variable names such as a+1, *foo* and number?.

Variables are symbols that have been bound to a value.

The first time a variable is used it should be bound using the := operator:

simple-values.idio

a := #t
printf "a is %s\n" a

b := 101
printf "b is %s or %X or %b\n" b b b

c := 123e-2
printf "c is %s or %5.1f\n" c c

d := "Hello World"
printf "d is %s and %.3s\n" d d

e := current-output-handle
printf "(e) is %s\n" (e)
printf "e is %s\n" e

$ idio simple-values
a is #t
b is 101 or 65 or 1100101
c is 1.230000e+00 or   1.2
d is Hello World and Hel
(e) is #<H ofw!iF   1:"*stdout*":5:86>
e is #<PRIM current-output-handle>

Notice that e became bound to the same value that current-output-handle was bound to and so could be invoked in the same way, (e), to return the value.

Subsequently, you can re-bind a variable to a different value using the = operator. Re-binding variables might be frowned upon in certain circles but it is common enough in many paradigms:

re-assignment.idio

define (foo a) {

  desc := "positive"
  if (a lt 0) {
    desc = "negative"
  }

  printf "%d is %s\n" a desc
}

foo 10
foo -10

$ idio re-assignment
10 is positive
-10 is negative

if, like all expressions, returns a value so we could have defined foo as:

define (foo a) {

  desc := if (a lt 0) "negative" "positive"

  printf "%d is %s\n" a desc
}

or not even created the local variable, desc and put the if expression (in parentheses) on the end of the printf expression.

Readability is always a concern.

Last built at 2024-12-21T07:11:32Z+0000 from 77077af (dev) for Idio 0.3