Rationale for the ANSI C Programming Language. Silicon Press. 1990. p. 31. ISBN0-929306-07-4., 3.1.4 String literals: "A long string can be continued across multiple lines by using the backslash-newline line continuation, but this practice requires that the continuation of the string start in the first position of the next line. To permit more flexible layout, and to solve some preprocessing problems (see §3.8.3), the Committee introduced string literal concatenation. Two string literals in a row are pasted together (with no null character in the middle) to make one combined string literal. This addition to the C language allows a programmer to extend a string literal beyond the end of a physical line without having to use the backslash-newline mechanism and thereby destroying the indentation scheme of the program. An explicit concatenation operator was not introduced because the concatenation is a lexical construct rather than a run-time operation."
Rationale for the ANSI C Programming Language. Silicon Press. 1990. p. 6566. ISBN0-929306-07-4., 3.8.3.2 The # operator: "The # operator has been introduced for stringizing. It may only be used in a #define expansion. It causes the formal parameter name following to be replaced by a string literal formed by stringizing the actual argument token sequence. In conjunction with string literal concatenation (see §3.1.4), use of this operator permits the construction of strings as effectively as by identifier replacement within a string. An example in the Standard illustrates this feature."
Rationale for the ANSI C Programming Language. Silicon Press. 1990. p. 31. ISBN0-929306-07-4., 3.1.4 String literals: "A long string can be continued across multiple lines by using the backslash-newline line continuation, but this practice requires that the continuation of the string start in the first position of the next line. To permit more flexible layout, and to solve some preprocessing problems (see §3.8.3), the Committee introduced string literal concatenation. Two string literals in a row are pasted together (with no null character in the middle) to make one combined string literal. This addition to the C language allows a programmer to extend a string literal beyond the end of a physical line without having to use the backslash-newline mechanism and thereby destroying the indentation scheme of the program. An explicit concatenation operator was not introduced because the concatenation is a lexical construct rather than a run-time operation."
Rationale for the ANSI C Programming Language. Silicon Press. 1990. p. 6566. ISBN0-929306-07-4., 3.8.3.2 The # operator: "The # operator has been introduced for stringizing. It may only be used in a #define expansion. It causes the formal parameter name following to be replaced by a string literal formed by stringizing the actual argument token sequence. In conjunction with string literal concatenation (see §3.1.4), use of this operator permits the construction of strings as effectively as by identifier replacement within a string. An example in the Standard illustrates this feature."
C++11 draft standard, "Working Draft, Standard for Programming Language C++"(PDF)., 2.2 Phases of translation [lex.phases], p. 17: "6. Adjacent string literal tokens are concatenated." and 2.14.5 String literals [lex.string], note 13, p. 28–29: "In translation phase 6 (2.2), adjacent string literals are concatenated."
The Python Language Reference, 2. Lexical analysis, 2.4.2. String literal concatenation: "Multiple adjacent string literals (delimited by whitespace), possibly using different quoting conventions, are allowed, and their meaning is the same as their concatenation."
The Python Language Reference, 2. Lexical analysis, 2.4.2. String literal concatenation: "Note that this feature is defined at the syntactical level, but implemented at compile time. The ‘+’ operator must be used to concatenate string expressions at run time."
The Python Language Reference, 2. Lexical analysis, 2.4.2. String literal concatenation: "This feature can be used to reduce the number of backslashes needed, to split long strings conveniently across long lines, or even to add comments to parts of strings, for example:
