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calc: Strings

 
 5.7 Strings
 ===========
 
 Character strings are not a special data type in the Calculator.
 Rather, a string is represented simply as a vector all of whose elements
 are integers in the range 0 to 255 (ASCII codes).  You can enter a
 string at any time by pressing the ‘"’ key.  Quotation marks and
 backslashes are written ‘\"’ and ‘\\’, respectively, inside strings.
 Other notations introduced by backslashes are:
 
      \a     7          \^@    0
      \b     8          \^a-z  1-26
      \e     27         \^[    27
      \f     12         \^\\   28
      \n     10         \^]    29
      \r     13         \^^    30
      \t     9          \^_    31
                        \^?    127
 
 Finally, a backslash followed by three octal digits produces any
 character from its ASCII code.
 
    Strings are normally displayed in vector-of-integers form.  The ‘d "’
 (‘calc-display-strings’) command toggles a mode in which any vectors of
 small integers are displayed as quoted strings instead.
 
    The backslash notations shown above are also used for displaying
 strings.  Characters 128 and above are not translated by Calc; unless
 you have an Emacs modified for 8-bit fonts, these will show up in
 backslash-octal-digits notation.  For characters below 32, and for
 character 127, Calc uses the backslash-letter combination if there is
 one, or otherwise uses a ‘\^’ sequence.
 
    The only Calc feature that uses strings is “compositions”; 
 Compositions.  Strings also provide a convenient way to do conversions
 between ASCII characters and integers.
 
    There is a ‘string’ function which provides a different display
 format for strings.  Basically, ‘string(S)’, where S is a vector of
 integers in the proper range, is displayed as the corresponding string
 of characters with no surrounding quotation marks or other
 modifications.  Thus ‘string("ABC")’ (or ‘string([65 66 67])’) will look
 like ‘ABC’ on the stack.  This happens regardless of whether ‘d "’ has
 been used.  The only way to turn it off is to use ‘d U’ (unformatted
 language mode) which will display ‘string("ABC")’ instead.
 
    Control characters are displayed somewhat differently by ‘string’.
 Characters below 32, and character 127, are shown using ‘^’ notation
 (same as shown above, but without the backslash).  The quote and
 backslash characters are left alone, as are characters 128 and above.
 
    The ‘bstring’ function is just like ‘string’ except that the
 resulting string is breakable across multiple lines if it doesn’t fit
 all on one line.  Potential break points occur at every space character
 in the string.
 

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