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Some minor updates for 15 years later.
author David A. Holland
date Tue, 31 May 2022 01:45:26 -0400
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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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2 <HTML>
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3 <HEAD>
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4 <TITLE>DOS Script Language</TITLE>
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5 </HEAD>
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6
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7
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8 <BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
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9 TEXT="#000000" LINK="#0033CC"
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10 VLINK="#CC0033" ALINK="#CC0099">
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11
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12 <P>
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13 <IMG ALIGN="right" SRC="../images/agrsl6c.gif" ALT="AnaGram"
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14 WIDTH=124 HEIGHT=30 >
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15 <BR CLEAR="all">
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16 Back to <A HREF="../index.html">Index</A>
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17 <P>
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18 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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19 WIDTH=1010 HEIGHT=2 >
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20 <P>
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21
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22 <H1>DOS Script Language </H1>
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23
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24 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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25 WIDTH=1010 HEIGHT=2 >
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26 <P>
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27 <H2>Introduction</H2>
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28 <P>
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29 DSL is a script language, written in AnaGram, which provides
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30 powerful extensions to the batch processing facilities
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31 available with DOS batch files.
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32 <P>
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33 DSL was built in large part by combining components from
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34 other grammars. Although the grammar for DOS command lines
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35 and for screen displays was written explicitly for DSL, just
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36 about everything else was borrowed from other grammars.
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37 <P>
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38 DSL has been tested using Borland C++, V4.52, and Watcom C++,
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39 V10.6. #ifdef statements have been used where necessary to
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40 support both compilers. V10.6 can be used to produce either
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41 16 or 32 bit executables. If you use Watcom, be sure to
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42 specify a stack size of at least 16K bytes.
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43 <P>
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44 DSL cannot be used with Microsoft Visual C++, since MSVC V1.5
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45 does not support templates and V4.x and subsequent releases do
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46 not support DOS.
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47 <P>
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48 <!-- not yet true
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49 DSL has been arranged so it will compile under Unix, but it
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50 will not run in any useful fashion.
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51 -->
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52 <P>
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53 DSL was written as part of the AnaGram 1.x installer; it is
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54 now obsolete but retains certain features of interest.
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55 <P>
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56
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57 <H2> Features of DSL </H2>
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58 <UL>
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59 <LI> DOS command line interpreter with substitutable
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60 parameters, redirection and pipelines. </LI>
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61 <LI> Screen builder for interactive parameter specification. </LI>
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62 <LI> String and integer variables, expressions and comparisons </LI>
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63 <LI> DOS for statement. </LI>
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64 <LI> Nested if and while statements. </LI>
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65 </UL>
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66 <P>
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67
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68 <H2> Screen Description </H2>
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69 The screen description syntax allows you to specify the
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70 size, location, and colors of windows plus two kinds of data
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71 entry fields: data fields and buttons.
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72 <P>
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73 A data field description consists of a prompt, an
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74 explanation, a variable name for the data, and a default
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75 value expression. The expression is evaluated for the
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76 default value of the data whenever the screen is refreshed.
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77 This means it can be modified as data entry is proceeding,
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78 based on fresh information.
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79 <P>
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80 A button description consists of a prompt, an explanation,
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81 and an action field. The action field consists of any
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82 sequence of DOS commands enclosed in brackets. Each command
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83 should be on a new line.
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84 <P>
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85
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86
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87 <H2> Variables and Constants </H2>
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88 DSL has three types of variables: undeclared, integer, and
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89 string variables.
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90 <P>
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91 Undeclared variables may be used in DOS commands and screen
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92 descriptions. They may appear on the left side of assignment
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93 statements. The names of undeclared variables are simple
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94 "literals", that is, sequences of characters drawn from the
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95 set "text char". If an undeclared variable does not have a
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96 value assigned to it, either by an assignment statement or
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97 by its use in a screen, it will be taken literally.
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98 <P>
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99 Integer and string variables must be declared. They may be
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100 used in expressions and comparisons. In particular they may
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101 be used in if statements and while statements.
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102 <P>
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103 DSL supports 32 bit integer arithmetic using essentially the
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104 expression logic in C with a slight modification for string
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105 comparison. Integer constants may be decimal, octal,
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106 hexadecimal or character constants, using the C conventions.
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107 <P>
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108 Beside simple "literals", DSL supports "string literals"
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109 which follow the rules for string literals in C, and
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110 parenthesized literals. Parenthesized literals are enclosed
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111 in parentheses and may contain any characters whatsoever,
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112 the only restriction being that any nested parentheses must
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113 balance. When a parenthesized literal is evaluated, the outer
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114 parentheses are stripped.
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115 <P>
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116
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117
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118 <H2> Theory of Operation </H2>
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119 DSL is a purely interpretive program. In some circumstances,
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120 statements and commands are executed as they are scanned. In
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121 other cases, where execution is to be delayed or is
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122 conditional, they are simply passed over on first scan and
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123 then copied. DSL then calls itself recursively to execute
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124 the copy when it is appropriate.
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125 <P>
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126 Note that if the parser you build from <tt>dsl.syn</tt> is called
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127 without any arguments, it looks for a script with the same
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128 name as the executable. Thus, to make an install program
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129 that picks up the install script without any arguments, you
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130 simply rename <tt>dsl.exe</tt> to <tt>install.exe</tt>. Then
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131 when you run it
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132 without any arguments it will run the <tt>install.dsl</tt> script.
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133 <P>
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134 DSL makes extensive use of a number of simple data
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135 structures defined in the <tt>oldclasslib</tt> directory of
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136 the AnaGram distribution. The most important
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137 of these are the string accumulators, the string
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138 dictionaries, and the stacks.
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139 <P>
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140 <P>
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141 The remainder of this document provides a brief overview of
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142 the principal data structures used by DSL and the most
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143 important nonterminal tokens in the DSL grammar.
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144 <P>
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145
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146 <H2> Stacks </H2>
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147 <H4>as</H4>
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148 This is a stack of pointers to actions which have been
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149 identified in the parse. An action is a block of commands
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150 enclosed in braces {}. The action pointer records a
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151 pointer to the beginning of the action, as well as the line
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152 and column number where the action begins. The use of a stack
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153 allows nested actions.
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154
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155 <H4>is</H4>
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156 This is a stack of integers. Its only use is for recording
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157 string concatenation sequences, where the integers stacked
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158 are the string dictionary indices of the items to be
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159 concatenated.
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160
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161 <H4>ps</H4>
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162 This stack accumulates pointers to the parameter strings for
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163 a call to a DOS function.
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164 <P>
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165
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166 <H2> Symbol Table </H2>
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167 Three data structures are used to gather and maintain
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168 symbol table information. The first is a string accumulator,
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169 sa, which is used for temporary storage for all strings that
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170 are recognized by the parser. The string dictionary, sd, is
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171 used to identify strings. The array st contains specific
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172 information about strings indexed in sd.
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173 <P>
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174
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175 <H2> Nonterminal Tokens </H2>
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176 <H4> action text </H4>
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177 "action text" is any sequence of commands enclosed in
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178 balanced braces. action text may be used in most contexts
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179 where a string value is expected. In these situations, the
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180 enclosed commands are executed, the content of stdout is
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181 captured as a string, and is returned as the value of the
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182 action text. For example, {DIR} returns a string containing
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183 the file directory for the current directory.
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184 <P>
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185 <H4> action text head </H4>
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186 "action text head" is simply action text up to the
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187 terminating right brace.
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188 <P>
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189 <H4> assignment </H4>
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190 Normally, an identifier on the left, an expression on the
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191 right, the kind of expression depending on the identifier.
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192 Note that using the '@' operator you can modify characters
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193 inside a string.
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194 <P>
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195 <H4> built_in name </H4>
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196 Note that there are a number of arithmetic functions built
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197 into DSL.
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198 <P>
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199 <H4> button line </H4>
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200 A button line is a line on a screen display that controls
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201 the further execution of the script. The description of the
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202 button line requires a label, an explanation, and an action
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203 to be performed when the button is selected.
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204 <P>
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205 <H4> character constant </H4>
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206 Follows the same rules as in C.
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207 <P>
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208 <H4> command </H4>
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209 This is the syntax for a DOS command line, allowing
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210 redirected input and output and piped commands.
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211 <P>
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212 <H4> command sequence </H4>
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213 A command sequence is any sequence of statements and
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214 if statements that ends with a statement.
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215 <P>
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216 <H4> comment </H4>
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217 This is an ordinary C-style comment.
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218 <P>
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219 <H4> comment head </H4>
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220 The beginning of a comment. Normally everything but the
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221 terminating <CODE> */ </CODE>. If a nested comment is found, the rule
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222 "comment head, comment" should reduce to "comment head" if it
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223 is desired that comments nest. If this rule reduces to
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224 "comment", the terminating <CODE> */ </CODE> of the nested comment will
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225 serve to terminate the outer level comment as well, and
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226 comments will not nest. See the discussion in
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227 AnaGram\SBB.DOC or in Appendix D, <A href="sbb-doc.html">Syntactic Building
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228 Blocks</A>, in the AnaGram User's Guide.
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229 <P>
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230 <H4> conditional exp </H4>
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231 This is the standard C expression logic modified as follows:
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232 Integer arithmetic only; string comparison allowed; no
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233 auto-increment or auto-decrement operators.
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234 <P>
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235 <H4> declaration </H4>
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236 Three kinds of declarations: actions can be used like DOS
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237 commands. The definition lists substitutable arguments which
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238 can be supplied at execution time.
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239 <P>
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240 Variables which are declared to be strings or ints must
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241 satisfy the usual naming conventions of program variables in
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242 order to avoid confusion in the expression logic.
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243
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244 <P>
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245 <H4> eol </H4>
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246 eol is a newline character, optionally preceded by a C++
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247 style comment beginning with //. eol is not included in "ws"
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248 because it is used as a statement terminator.
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249 <P>
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250 <H4> execution block </H4>
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251 A sequence of DOS commands enclosed within braces. The
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252 difference between an execution block and "action text" is
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253 that the commands in an execution block are performed as
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254 they are encountered, while "action text" is saved up for
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255 later execution.
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256 <P>
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257 <H4> for statement </H4>
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258 Modeled on the for statement in the DOS batch language
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259 rather than on the for statement in C.
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260 <P>
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261 <H4> formula </H4>
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262 A sequence of "words", joined by concatenation operators
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263 ('#'). When the formula is evaluated, the words are
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264 identified in the string dictionary, and their values are
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265 concatenated. If a word has no entry in the dictionary its
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266 literal value is used. Formulas are used in the
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267 specification of the fields in a query line.
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268 <P>
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269 <H4> identifier </H4>
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270 A DOS command
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271 <P>
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272 <H4> if condition </H4>
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273 The keyword if and a conditional expression within
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274 parentheses.
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275 <P>
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276 <H4> if sequence </H4>
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277 An if sequence is any direct sequence of statements and if
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278 statements that ends with an if statement. The difference
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279 between an "if sequence" and a "command sequence" is that an
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280 else clause may follow the "if sequence".
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281 <P>
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282 <H4> if statement </H4>
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283 An "if condition" followed by "action text". Note that a
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284 simple statement is not allowed.
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285 <P>
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286 <H4> integer constant </H4>
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287 Follows the same rules as an integer constant in C, allowing
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288 decimal, octal and hex constants.
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289 <P>
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290 <H4> integer variable </H4>
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291 An variable that has been declared with an "int" statement.
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292 <P>
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293 <H4> literal </H4>
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294 A "literal" is any sequence of characters that does not
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295 include white space; parentheses, brackets, or braces;
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296 quotation marks or newline characters; redirection or pipe
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297 operators, or '#' or '='. Essentially, a "literal" is
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298 anything that would make sense on a DOS command line.
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299 <P>
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300 <H4> literals </H4>
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301 A sequence of instances of "literal" separated by white
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302 space. This sequence is used only in the definition of a
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303 named action. The first literal is the name of the action.
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304 Subsequent literals are the local names of the substituble
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305 parameters.
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306 <P>
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307 <H4> name </H4>
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308 Used for int and string variables. The conventional rules
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309 for variable names in programming language are used.
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310 <P>
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311 <H4> parameter string </H4>
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312 parameter string is essentially the same as "string", except
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313 that any of the concatenated strings may be action text,
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314 that is the result of executing a DOS command and capturing
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315 stdout.
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316 <P>
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317 <H4> parameter word </H4>
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318 parameter word is essentially the same as "word", except
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319 that it may also be action text, that is, the result of
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320 executing a DOS command and capturing stdout.
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321 <P>
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322 <H4> parameters </H4>
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323 The parameters for a DOS command
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324 <P>
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325 <H4> paren string </H4>
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326 A parenthesized string is any sequence of characters within
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327 parentheses, with the only restriction that any nested
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328 parentheses must balance. When evaluated, the outer set of
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329 parentheses is stripped. Parenthesized strings are for use
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330 in DOS command lines in those situations where the
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331 restrictions on "literal" are excessively onerous.
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332 <P>
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333 <H4> piped command </H4>
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334 A "piped command", here, is any DOS command, for which
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335 stdout must be captured and redirected.
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336 <P>
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337 <H4> primary exp </H4>
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338 These are the basic elements of expressions. Note that you
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339 may use the '@' operator to extract a character from a
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340 string. You need not use parentheses on the right if you use
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341 a simple index variable or integer constant. If you wish to
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342 use a more complex expression, you must use parentheses.
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343 <P>
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344 <H4> query line </H4>
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345 This is the description of a line on a screen into which the
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346 user is invited to enter some data. The description requires
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347 four elements: the variable into which the data is to be
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348 stored, the default value for the data, a prompt which
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349 identifies the data, and an explanation field which provides
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350 a fuller explanation of the data required.
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351 <P>
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352 After data has been entered for a particular query line, all
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353 elements of other query lines are reevaluated in case their
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354 defaults have been defined in terms of the data entered.
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355 <P>
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356 <H4> screen description </H4>
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357 A sequence of screen items enclosed in braces. A screen
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358 description is executed as it is read. If you wish to
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359 describe a screen for later use, incorporate it in an
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360 "action declaration".
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361 <P>
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362 A screen description requires a number of "screen items".
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363 These items consist of the title, the color specifications,
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364 the size and location of the window, and a number of query
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365 lines and button lines.
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366 <P>
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367 The layout of the screen is done automatically.
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368 <P>
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369
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370 <H4> script file </H4>
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371 This is the grammar token. It describes the entire script
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372 file.
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373 <P>
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374 <H4> statement </H4>
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375 Statements include DOS commands plus declarations,
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376 assignment statements, control statements and screen
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377 descriptions. Note the repetition of the while statement.
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378 This stratagem allows a very simple implementation of
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379 looping logic.
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380 <P>
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381 <H4> string </H4>
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382 "string" is a concatenation of "word"s, using the
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383 concatenation operator, '#'.
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384 <P>
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385 <H4> string exp </H4>
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386 Syntactically the same as "string", except that the
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387 primitive elements are different.
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388 <P>
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389 <H4> string literal </H4>
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390 Follows exactly the same rules as string literals in C.
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391 <P>
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392 <H4> string primary </H4>
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393 Note that you may use '@' to extract a substring from a
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394 string.
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395 <P>
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396 <H4> string variable </H4>
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397 A variable that has been declared with a "string"
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398 declaration.
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399 <P>
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400 <H4> undeclared variable </H4>
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401 A variable that has not been declared, but has been defined
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402 only by its use.
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403 <P>
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404 <H4> while statement </H4>
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405 Like the C while statement except that the scope of the
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406 while statement must be contained within braces. The braces
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407 are mandatory.
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408 <P>
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409 <H4> word </H4>
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410 One or more "words" can be concatenated using the '#'
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411 operator to create a "string". The command identifer in a
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412 DOS command line is determine by evaluating such a string.
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413 The "formula" used for the default values in screens is also
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414 a sequence of one or more "words", joined by '#', with the
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415 difference that the actual evaluation of the string is
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416 deferred until the screen is displayed, and then is
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417 recalculated after each field is entered.
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418 <P>
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419 Note that "subscripts" are allowed.
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420 <P>
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421 <H4> ws </H4>
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422 ws (white space) consists of blanks, tabs and nested C-style
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423 comments.
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424 </P>
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425
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426 <BR>
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427
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428 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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429 WIDTH=1010 HEIGHT=2 >
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430 <P>
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431 <IMG ALIGN="right" SRC="../images/pslrb6d.gif" ALT="Parsifal Software"
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432 WIDTH=181 HEIGHT=25>
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433 <BR CLEAR="right">
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434 <P>
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435 Back to <A HREF="../index.html">Index</A>
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436 <P>
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437 <ADDRESS><FONT SIZE="-1">
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438 AnaGram parser generator - examples<BR>
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439 DOS Script Language <BR>
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440 Copyright &copy; 1993-1999, Parsifal Software. <BR>
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441 All Rights Reserved.<BR>
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442 </FONT></ADDRESS>
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443
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444 </BODY>
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445 </HTML>