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# string_length(+String, -Length)

Succeeds if Length is the length of the string String.

String
  String.
Length
  Integer or variable.

## Description

The length of the string String is unified with Length.

Note that (like all predicates that return a number as their last argument), this predicate can be used as a function inside arithmetic expressions.

### Modes and Determinism

- string_length(+, -) is det

### Exceptions

(4) instantiation fault
  String is not instantiated (non-coroutine mode only).
(5) type error
  String is instantiated, but not to a string.
(5) type error
  Length is neither an integer nor a variable.

## Examples

    Success:
          string_length("Peter ",X).  (gives X=6).
          string_length("Peter ",6).
          string_length("401.35",6).

    Fail:
          string_length("Peter",6).

    Error:
          string_length(Str,Len).            (Error 4).
          string_length(Str,6).              (Error 4).
          string_length("small",5.0).        (Error 5).
          string_length(Str,instantiated).   (Error 5).
          string_length(Str,46.2)            (Error 5).
          string_length('this one',L).       (Error 5).

## See Also

append_strings / 3, atom_length / 2, concat_strings / 3