Literals/String: Difference between revisions

Fortran IV introduced a text literal, specified within apostrophes, with two apostrophes in a row indicating an apostrophe within the text. Later, either an apostrophe or a double quote could be used to start a text string (and the same one must be used to end it) so that if one or the other were desired within a text literal, the other could be used as its delimiters. If both were desired, then there would be no escape from doubling for one. Because spaces are significant within text literals, a long text literal continued on the next line would have the contents of column seven of the continuation line immediately following the contents of column 72 of the continued line. F90- formalisedexcept an opportunitythat (for free-formatsome sourcecompilers reading disc files;) manyif compilerssuch hadlines alsodid allowednot usageextend beyondto column 72 (because trailing spaces were trimmed from the records) rather less text would be defined. So, even though this is in fixed-format (or card image) style, again misinterpreted by the syntax highlighter, <lang Fortran> BLAH = "

Within the text literal, any character whatever may be supplied as texttextEvidently, the syntax highlighter here does not recognise the Hollerith style usage. Nor do some compilers, even if in its original home within FORMAT statements. grist, according to the encodement recognised by the card reader as this was a fixed-format file - cards have an actual physical size. This applied also to source text held in disc files, as they were either fixed-size records or, for variable-length records, records had a length specification and the record content was not involved. Variable-length records were good for omitting the storage of the trailing spaces on each line, except that the sequence numbers were at the end of the line! In this case they might be omitted (unlike a card deck, a disc file's records are not going to be dropped) or there may be special provision for them to be at the start of each line, with the source text's column one staring in column nine of the record. But, for the likes of paper tape, the question "How long is a record?" has no natural answer, and record endings were marked by a special symbol. Such a symbol (or symbol sequence) could not appear within a record, such as within a text literal and be taken as a part of the text. This style has been followed by the ASCII world, with variously CR, CRLF, LFCR and CR sequences being used to mark end-of-record. Such characters cannot be placed within a text literal, but the CHAR(n) function makes them available in character expressions. Some compilers however corrupt the "literal" nature of text ''literals'' by allowing escape sequences to do so, usually in the style popularised by C, thus \n, and consequently, \\ should a single \ be desired.