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Annotation of 43BSD/contrib/icon/man/man1/rsg.1, revision 1.1

1.1     ! root        1: .so tmac.ilib
        !             2: .TH RSG 1 "The University of Arizona \- 5/16/83"
        !             3: .SH NAME
        !             4: rsg \- generate random sentences
        !             5: .SH SYNOPSIS
        !             6: \f3rsg\fP [\f3\-l\fI n\fR] [\f3\-l \fIn\fR] [\f3\-t\fR]
        !             7: .SH DESCRIPTION
        !             8: \fIRsg\fR generates randomly selected sentences from a grammar specified by
        !             9: the user.
        !            10: .PP
        !            11: The following options may appear in any order:
        !            12: .IP "\f3\-s\fI n\fR"
        !            13: Set the seed for random generation to \fIn\fR.
        !            14: The default seed is 0.
        !            15: .IP "\f3\-l\fI n\fR"
        !            16: Terminate generation if the number of symbols remaining to be processed
        !            17: exceeds \fIn\fR. There is no default limit.
        !            18: .IP \f3\-t\fR
        !            19: Trace the generation of sentences. Trace output goes to standard error
        !            20: output.
        !            21: .PP
        !            22: \fIRsg\fR works interactively, allowing the user to build, test, modify,
        !            23: and save grammars. Input to \fIrsg\fR consists of various kinds of
        !            24: specifications, which can be intermixed:
        !            25: .PP
        !            26: \fIProductions\fR define nonterminal symbols in a syntax similar to 
        !            27: the rewriting rules of BNF with various alternatives consisting
        !            28: of the concatenation of nonterminal and terminal symbols.
        !            29: .PP
        !            30: \fIGeneration specifications\fR cause the generation of a specified
        !            31: number of sentences from the language defined by a given nonterminal
        !            32: symbol.
        !            33: .PP
        !            34: \fIGrammar output specifications\fR cause the definition of a
        !            35: specified nonterminal or the entire current grammar to be written
        !            36: to a given file.
        !            37: .PP
        !            38: \fISource specifications\fR cause subsequent input to be read from
        !            39: a specified file.
        !            40: .PP
        !            41: In addition, any line beginning with \*M#\fR is considered to be
        !            42: a comment, while any line beginning with \*M=\fR causes the rest
        !            43: of that line to be used as a prompt to the user whenever \fIrsg\fR
        !            44: is ready for input (there normally is no prompt). A line consisting
        !            45: of a single \*M=\fR stops prompting.
        !            46: .SH \0\0\0Productions
        !            47: Examples of productions are:
        !            48: .DS
        !            49: <expr>::=<term>|<term>+<expr>
        !            50: <term>::=<element>|<element>*<term>
        !            51: <element>::=x|y|z|(<expr>)
        !            52: .DE
        !            53: Productions may occur in any order. The definition for a nonterminal
        !            54: symbol can be changed by specifying a new production for it.
        !            55: .PP
        !            56: There are a number of special devices to facilitate the definition of
        !            57: grammars, including eight predefined, built-in nonterminal symbols:
        !            58: .nf
        !            59: .sp 1
        !            60: .ta .5i 1.5i
        !            61:        symbol  definition
        !            62: .sp .5
        !            63:        \*M<lb> <
        !            64:        <rb>    >
        !            65:        <vb>    |
        !            66:        <nl>\fR newline
        !            67:        \*M<>\fR        empty string
        !            68:        \*M<&lcase>\fR  any single lowercase letter
        !            69:        \*M<&ucase>\fR  any single uppercase letter
        !            70:        \*M<&digit>\fR  any single digit
        !            71: .sp 1
        !            72: .fi
        !            73: In addition, if the string between a \*M<\fR and \*M>\fR
        !            74: begins and
        !            75: ends with a single quotation mark, that construction stands for
        !            76: any single character between the quotation marks. For example,
        !            77: .DS
        !            78: <'xyz'>
        !            79: .DE
        !            80: is equivalent to
        !            81: .DS
        !            82: x|y|z
        !            83: .DE
        !            84: Finally, if the name of a nonterminal symbol between the \*M<\fR and
        !            85: \*M>\fR begins with \*M?\fR, the user is queried during generation
        !            86: to supply a string for that nonterminal symbol. For example, in
        !            87: .DS
        !            88: <expr>::=<term>|<term>+<expr>|<?expr>
        !            89: .DE
        !            90: if the third alternative is encountered during generation, the user is
        !            91: asked to provide a string for \*M<expr>\fR.
        !            92: .SH \0\0\0Generation Specifications
        !            93: A generation specification consists of a nonterminal symbol
        !            94: followed by a nonnegative integer. An example is
        !            95: .DS
        !            96: <expr>10
        !            97: .DE
        !            98: which specifies the generation of 10 \*M<expr>\fRs. If the
        !            99: integer is omitted, it is assumed to be 1. Generated sentences
        !           100: are written to standard output.
        !           101: .SH \0\0\0Grammar Output Specifications
        !           102: A grammar output specification consists of a nonterminal symbol,
        !           103: followed by \*M\->\fR, followed by a file name. Such a specification
        !           104: causes the current definition of the nonterminal symbol to be
        !           105: written to the given file. If the file is omitted, standard output
        !           106: is assumed. If the nonterminal symbol is omitted, the entire grammar
        !           107: is written out. Thus,
        !           108: .DS
        !           109: \->
        !           110: .DE
        !           111: causes the entire grammar to be written to standard output.
        !           112: .SH \0\0\0Source Specifications
        !           113: A source specification consists of \*M@\fR followed by a file name.
        !           114: Subsequent input is read from that file. When an end of file is encountered,
        !           115: input reverts to the previous file. Input files can be nested.
        !           116: .SH DIAGNOSTICS
        !           117: Syntactically erroneous input lines are noted, but ignored.
        !           118: .PP
        !           119: Specifications for a file that cannot be opened are noted and treated as
        !           120: erroneous.
        !           121: .PP
        !           122: If an undefined nonterminal symbol is encountered during generation,
        !           123: an error message that identifies the undefined symbol is produced,
        !           124: followed by the partial sentence generated to that point. Exceeding
        !           125: the limit of symbols remaining to be generated as specified by
        !           126: the \f3\-l\fR option is handled in similarly.
        !           127: .SH CAVEATS
        !           128: Generation may fail to terminate because of a loop in the rewriting
        !           129: rules or, more seriously, because of the progressive accumulation
        !           130: of nonterminal symbols. The latter problem can be identified
        !           131: by using the \f3\-t\fR option and controlled by using the \f3\-l\fR
        !           132: option. The problem often can be circumvented by duplicating alternatives
        !           133: that lead to fewer rather than more nonterminal symbols. For
        !           134: example, changing
        !           135: .DS
        !           136: <expr>::=<term>|<term>+<expr>
        !           137: .DE
        !           138: to
        !           139: .DS
        !           140: <expr>::=<term>|<term>|<term>+<expr>
        !           141: .DE
        !           142: increases the probability of selecting \*M<term>\fR from 1/2 to 2/3.
        !           143: See the second reference listed below for a discussion of the general
        !           144: problem.
        !           145: .SH SEE ALSO
        !           146: .Ib
        !           147: pp. 211-219, 301-302.
        !           148: .PP
        !           149: Wetherell, C. S. ``Probabilistic Languages: A Review and Some Open
        !           150: Questions'', \fIComputer Surveys\fR, Vol. 12, No. 4 (1980), pp. 361-379.
        !           151: .SH AUTHOR
        !           152: Ralph E. Griswold

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