Next: , Previous: 2.5, Up: 2


2.6 String Literals

1
[A string_literal is formed by a sequence of graphic characters (possibly none) enclosed between two quotation marks used as string brackets. They are used to represent operator_symbols (see 6.1), values of a string type (see 4.2), and array subaggregates (see 4.3.3). {quoted string: See string_literal} ]

Syntax

2

string_literal::= "{string_element}"

3

string_element::= "" non_quotation_mark_graphic_character

4

A string_element is either a pair of quotation marks (""), or a single graphic_character other than a quotation mark.
Static Semantics

5
{sequence of characters (of a string_literal)} The sequence of characters of a string_literal is formed from the sequence of string_elements between the bracketing quotation marks, in the given order, with a string_element that is "" becoming a single quotation mark in the sequence of characters, and any other string_element being reproduced in the sequence.

6
{null string literal} A null string literal is a string_literal with no string_elements between the quotation marks.

     NOTES

7

 An end of line cannot appear in a string_literal.

7.1/2

 {00285AI95−00285−01} No transformation is performed on the sequence of characters of a string_literal.
Examples

8
Examples of string literals:

9/2

     {00433AI95−00433−01} "Message of the day:"
     
     ""                    −−  null string literal
     "   "A"   """"      −−  three string literals of length 1
     
     "Characters such as $, %, and are allowed in string literals"
     "Archimedes said ""[Unicode 917]
     [Unicode 973]
     [Unicode 961]
     [Unicode 951]
     [Unicode 954]
     [Unicode 945]
     """
     "Volume of cylinder (PIr²h) "
Wording Changes from Ada 83

9.a

The wording has been changed to be strictly lexical. No mention is made of string or character values, since string_literals are also used to represent operator_symbols, which don't have a defined value.

9.b

The syntax is described differently.
Wording Changes from Ada 95

9.c/2

{00285AI95−00285−01} We explicitly say that the characters of a string_literal should be used as is. In particular, no normalization or folding should be performed on a string_literal.