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Annotation of 43BSD/contrib/dipress/doc/intertext.me, revision 1.1

1.1     ! root        1: .bp
        !             2: .sh 1 "Introduction to the syntax of Intertext"
        !             3: .sh 2 Introduction
        !             4: .lp
        !             5: This section describes a language used to represent an Interpress master,
        !             6: called \fIIntertext\fP.  In order to make an Interpress master compact,
        !             7: an encoding scheme is used to represent the operators and the values.  
        !             8: Although this encoding uses less disk space and results in shorter
        !             9: transmission times, it is practically impossible to examine or edit an
        !            10: Interpress master.  For this reason, the utilities \fIiptotext\fP and
        !            11: \fItexttoip\fP represent the master in a language called \fIIntertext\fP.
        !            12: For someone to completely use the Interpress utilities and understand the
        !            13: output, an understanding of this language is necessary.  It is recommended
        !            14: that the reader of this section have a working knowledge of Interpress.
        !            15: .sh 2 Tokens
        !            16: .sh 3 "Keywords"
        !            17: .lp
        !            18: The keyword \*(lqHeader\*(rq indicates that the following string is the
        !            19: header that appears at the front of the Interpress file.  This keyword can
        !            20: only be used once at the top of the file.  It is not checked for validity.
        !            21: .sh 2 "Integers"
        !            22: .lp
        !            23: A series of digits optionally preceded by a plus or minus sign is an integer.
        !            24: .sh 2 "Short numbers"
        !            25: .lp
        !            26: Any integer that starts in the first column is translated into an Interpress 
        !            27: \fIshort number\fP.  This number must be in the range \(mi4000..28767.
        !            28: .sh 2 "Operators"
        !            29: .lp
        !            30: Any word that starts in the first column
        !            31: is translated into an operator, with the exceptions noted in \fIkeywords\fP.
        !            32: The \*(lqpseudo\*(rq operators are handled as follows.
        !            33: The word \*(lqBEGIN\*(rq marks
        !            34: the beginning of a block.  The word \*(lqEND\*(rq indicates the
        !            35: end of a block.  The character \*(lq{\*(rq indicates the beginning
        !            36: of a body and the character \*(lq}\*(rq indicates the end of a
        !            37: body.  All other words refer to an Interpress operator.  The names found in
        !            38: Appendix B of the \fIInterpress Electronic printing Standard\fP
        !            39: are recognized.  The case of the letters is insignificant.
        !            40: .sh 2 "Comments"
        !            41: .lp
        !            42: Anything that appears in parentheses is assumed to be a
        !            43: comment and is ignored.  These comments should not be confused with a
        !            44: comment sequence.
        !            45: .sh 2 "Sequences"
        !            46: .lp
        !            47: If the first
        !            48: character on the line is \*(lq>\*(rq then the remainder of the line
        !            49: describes a \fIsequence\fP.
        !            50: If the second character is also \*(lq>\*(rq then the
        !            51: sequence described is \fIlong\fP, otherwise it is \fIshort\fP.
        !            52: The keyword that starts
        !            53: in the third column describes the type of sequence.  The value of the
        !            54: sequence appears after the colon.  The following names are valid sequence
        !            55: names:  Comment, Identifier, Insert file, Integer, Rational, String.
        !            56: .sh 2 "Strings"
        !            57: .lp
        !            58: Strings are represented in the same way they are in C.
        !            59: A double quote is used to mark each end of the string
        !            60: and a backslash is used to indicate the start of a special
        !            61: character.  If a digit follows a backslash, it starts an octal number that
        !            62: does not exceed three digits.  This number is the octal value of the
        !            63: character represented.  For example, the string "a\e244b" consists of an
        !            64: ascii \*(lqa\*(rq followed by the octal value 244 and ending with an ascii
        !            65: \*(lqb\*(rq.  Two successive backslashes represents a single backslash and a
        !            66: backslash followed by a double quote represents a double quote.  It will not
        !            67: be uncommon in program listings to use strings like:
        !            68: "#include\ \e"file.h\e"".
        !            69: .sh 2 "Rationals"
        !            70: .lp
        !            71: A rational number is represented as a fraction with a slash separating the
        !            72: numerator and the denominator.
        !            73: For example:  \*(lq1/2\*(rq represents the rational 1 over 2.
        !            74: .sh 2 Format
        !            75: .sp
        !            76: Here is a Backus-Naur style grammar that describes the Intertext format
        !            77: (tokens are in italics, literals are contained in double quotes):
        !            78: .sp
        !            79: .(l
        !            80: Intertext ::= prelim body | body
        !            81: 
        !            82: prelim ::= file header | file | header
        !            83: 
        !            84: file ::= "File: " \fIstring\fP \fInl\fP
        !            85: 
        !            86: header ::= "Header: " \fIstring\fP \fInl\fP
        !            87: 
        !            88: body ::= line \fInl\fP\^ body | line \fInl\fP
        !            89: 
        !            90: line ::= \fIinteger\fP | \fIoperator\fP | short-long sequence
        !            91: 
        !            92: .ta \w'sequence ::= 'u
        !            93: sequence ::= "Comment: " \fIstring\fP |
        !            94:        "Identifier: " \fIidentifier\fP |
        !            95:        "Insert file: " \fIstring\fP |
        !            96:        "Integer: " \fIinteger\fP |
        !            97:        "Rational: " \fIinteger\fP\^ "/" \fIinteger\fP |
        !            98:        "String: " \fIstring\fP
        !            99: 
        !           100: short-long ::= "> " | ">>"
        !           101: .)l
        !           102: .sp
        !           103: The token \fInl\fP\^ is a newline or line terminator.
        !           104: The other italicized tokens are explained in the previous section.
        !           105: .sh 2 Omissions
        !           106: .lp
        !           107: There is currently no way to express large vectors or any
        !           108: of the pixel vectors.  There is also no way to specify a continued
        !           109: sequence.

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