# Euphoria - Sequences

A sequence is represented by a list of objects in brace brackets { }, separated by commas. A sequence can contain both atoms and other sequences. For example −

```{2, 3, 5, 7, 11, 13, 17, 19}
{1, 2, {3, 3, 3}, 4, {5, {6}}}
{{"Zara", "Ayan"}, 52389, 97.25}
{} -- the 0-element sequence
```

A single element of a sequence may be selected by giving the element number in square brackets. Element numbers start at 1.

For example, if x contains {5, 7.2, 9, 0.5, 13} then x[2] is 7.2. Suppose x[2] contains {11,22,33}, Now if we ask for x[2] we get {11,22,33} and if we ask for x[2][3] we get the atom 33.

## Example

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

sequence x
x = {1, 2, 3, 4}

for a = 1 to length(x) do
printf(1, "value of x[%d] = %d\n", {a, x[a]})
end for
```

Here length() is a Euphoria's built-in function which returns length of the sequence. Above example would produce following result −

```value of x[1] = 1
value of x[2] = 2
value of x[3] = 3
value of x[4] = 4
```

## Character String

A character string is just a sequence of characters. It may be entered in one of the two ways −

(a) Using double-quotes:

```"ABCDEFG"
```

(b) Using raw string notation −

```-- Using back-quotes
`ABCDEFG`

or

-- Using three double-quotes
"""ABCDEFG"""
```

Try following example to understand the concept −

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

sequence x
x = "ABCD"

for a = 1 to length(x) do
printf(1, "value of x[%d] = %s\n", {a, x[a]})
end for
```

This would produce following result −

```value of x[1] = A
value of x[2] = B
value of x[3] = C
value of x[4] = D
```

## String Arrays

An array of string can be implemented using Sequences as follows −

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

sequence x = {"Hello", "World", "Euphoria", "", "Last One"}

for a = 1 to length(x) do
printf(1, "value of x[%d] = %s\n", {a, x[a]})
end for
```

This would produce following result −

```value of x[1] = Hello
value of x[2] = World
value of x[3] = Euphoria
value of x[4] =
value of x[5] = Last One
```

## Euphoria Structures

A structure can be implemented using Sequences as follows −

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

sequence employee = {
{"John","Smith"},
45000,
27,
185.5
}

printf(1, "First Name = %s, Last Name = %s\n",
{employee[1][1],employee[1][2]} )
```

This would produce following result −

```First Name = John, Last Name = Smith
```

There are following operations which can be performed directly on sequences −

## Urinary Operation

When applied to a sequence, a unary operator is actually applied to each element in the sequence to yield a sequence of results of the same length.

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

sequence x
x = -{1, 2, 3, 4}

for a = 1 to length(x) do
printf(1, "value of x[%d] = %d\n", {a, x[a]})
end for
```

This would produce following result −

```value of x[1] = -1
value of x[2] = -2
value of x[3] = -3
value of x[4] = -4
```

## Arithmetic Operations

Almost all arithmetic operations can be performed on sequences as follows −

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

sequence x, y, a, b, c
x = {1, 2, 3}
y = {10, 20, 30}

a = x + y
puts(1, "Value of a = {")
for i = 1 to length(a) do
printf(1, "%d,", a[i])
end for
puts(1, "}\n")

b = x - y
puts(1, "Value of b = {")
for i = 1 to length(a) do
printf(1, "%d,", b[i])
end for
puts(1, "}\n")

c = x * 3
puts(1, "Value of c = {")
for i = 1 to length(c) do
printf(1, "%d,", c[i])
end for
puts(1, "}\n")
```

This would produce following result −

```Value of a = {11,22,33,}
Value of b = {-9,-18,-27,}
Value of c = {3,6,9,}
```

## Command Line Options

A user can pass command line options to a Euphoria script and it can be accessed as a sequence using command_line() function as follows −

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

sequence x

x = command_line()

printf(1, "Interpeter Name: %s\n", {x[1]} )

printf(1, "Script Name: %s\n", {x[2]} )

printf(1, "First Argument: %s\n", {x[3]})

printf(1, "Second Argument: %s\n", {x[4]})
```

Here printf() is a Euphoria's built-in function. Now if you would run this script as follows −

```\$eui test.ex "one" "two"
```

This would produce following result −

```Interpeter Name: /home/euphoria-4.0b2/bin/eui
Script Name: test.ex
First Argument: one
Second Argument: two
```