# Strings

Strings in RuLA represent text values. They are enclosed in double quotes.

## Creating Strings

Create a string by enclosing text in double quotes:

```
"Hello World"
"Customer Name"
""
```

An empty string (`""`) is valid and represents a string with no characters.

## String Manipulation

### Concatenation

Join strings together using `+` or `CONCAT`:

```
"Hello" + " " + "World"     # Results in "Hello World"
CONCAT("Hello", " World")   # Results in "Hello World"
```

### Accessing Characters

Access individual characters by index (0-based):

```
"Hello"[0]      # Returns "H"
"Hello"[4]      # Returns "o"
```

### Slicing

Extract a portion of a string:

```
SLICE("Hello World", 0, 5)     # Returns "Hello"
LEFT("Hello World", 5)         # Returns "Hello"
RIGHT("Hello World", 5)        # Returns "World"
```

### Case Conversion

```
LOWER("Hello World")           # Returns "hello world"
UPPER("Hello World")           # Returns "HELLO WORLD"
```

### Trimming Whitespace

```
TRIM("  hello  ")              # Returns "hello"
TRIM_LEFT("  hello")           # Returns "hello"
```

## Useful String Functions

| Function                                                                      | Description                       | Example                                  |
| ----------------------------------------------------------------------------- | --------------------------------- | ---------------------------------------- |
| [`LEN`](/rule-language/operators/string-operators/len.md)                     | Returns the number of characters  | `LEN("abc")` → `3`                       |
| [`CONCAT`](/rule-language/operators/string-operators/concat.md)               | Joins multiple strings            | `CONCAT("a", "b")` → `"ab"`              |
| [`LOWER`](/rule-language/operators/string-operators/lower.md)                 | Converts to lowercase             | `LOWER("ABC")` → `"abc"`                 |
| [`UPPER`](/rule-language/operators/string-operators/upper.md)                 | Converts to uppercase             | `UPPER("abc")` → `"ABC"`                 |
| [`TRIM`](/rule-language/operators/string-operators/trim.md)                   | Removes whitespace from both ends | `TRIM(" a ")` → `"a"`                    |
| [`LEFT`](/rule-language/operators/string-operators/left.md)                   | First n characters                | `LEFT("hello", 2)` → `"he"`              |
| [`RIGHT`](/rule-language/operators/string-operators/right.md)                 | Last n characters                 | `RIGHT("hello", 2)` → `"lo"`             |
| [`SLICE`](/rule-language/operators/string-operators/slice.md)                 | Extract substring                 | `SLICE("hello", 1, 3)` → `"el"`          |
| [`REPLACE`](/rule-language/operators/string-operators/replace.md)             | Replace occurrences               | `REPLACE("a-b", "-", "/")` → `"a/b"`     |
| [`SPLIT`](/rule-language/operators/string-operators/split.md)                 | Split into list                   | `SPLIT("a,b", ",")` → `["a", "b"]`       |
| [`STARTS_WITH`](/rule-language/operators/string-operators/starts_with.md)     | Check prefix                      | `STARTS_WITH("abc", "ab")` → `True`      |
| [`ENDS_WITH`](/rule-language/operators/string-operators/ends_with.md)         | Check suffix                      | `ENDS_WITH("abc", "bc")` → `True`        |
| [`JOIN`](/rule-language/operators/string-operators/join.md)                   | Join list into string             | `JOIN(["a", "b"], "-")` → `"a-b"`        |
| [`FORMAT_NUMBER`](/rule-language/operators/string-operators/format_number.md) | Format as string                  | `FORMAT_NUMBER(3.14159, 2)` → `"3.14"`   |
| [`LEVENSHTEIN`](/rule-language/operators/string-operators/levenshtein.md)     | Edit distance                     | `LEVENSHTEIN("kitten", "sitting")` → `3` |
| [`PAD_LEFT`](/rule-language/operators/string-operators/pad_left.md)           | Pad on left                       | `PAD_LEFT("5", 3, "0")` → `"005"`        |
| [`PAD_RIGHT`](/rule-language/operators/string-operators/pad_right.md)         | Pad on right                      | `PAD_RIGHT("5", 3, "0")` → `"500"`       |
| [`TRIM_LEFT`](/rule-language/operators/string-operators/trim_left.md)         | Removes whitespace from start     | `TRIM_LEFT(" hello")` → `"hello"`        |

## String Comparison

Compare strings using standard operators:

```
"abc" = "abc"           # True (exact match)
"abc" != "def"          # True
"abc" contains "b"      # True
"abc" matches "a.*c"    # True (regex match)
```


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