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1 " |
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2 COPYRIGHT (c) 1993 by Claus Gittinger |
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3 All Rights Reserved |
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4 |
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5 This software is furnished under a license and may be used |
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6 only in accordance with the terms of that license and with the |
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7 inclusion of the above copyright notice. This software may not |
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8 be provided or otherwise made available to, or used by, any |
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9 other person. No title to or ownership of the software is |
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10 hereby transferred. |
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11 " |
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12 |
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13 Parser subclass:#Explainer |
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14 instanceVariableNames:'' |
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15 classVariableNames:'' |
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16 poolDictionaries:'' |
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17 category:'System-Compiler' |
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18 ! |
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19 |
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20 Explainer comment:' |
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21 |
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22 COPYRIGHT (c) 1993 by Claus Gittinger |
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23 All Rights Reserved |
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24 |
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25 $Header: /cvs/stx/stx/libcomp/Explainer.st,v 1.1 1993-10-13 00:25:45 claus Exp $ |
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26 '! |
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27 |
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28 !Explainer class methodsFor:'documentation'! |
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29 |
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30 documentation |
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31 " |
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32 a very simple explainer - much more should be added ... |
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33 " |
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34 ! ! |
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35 |
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36 !Explainer class methodsFor:'explaining'! |
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37 |
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38 explain:someText in:source forClass:aClass |
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39 "this is just a q&d implementation - there could be much more. |
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40 Given a source and a substring of it, return a string containing |
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41 an explanation." |
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42 |
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43 |parser variables v c string sym list count tmp |
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44 commonSuperClass| |
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45 |
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46 string := someText withoutSeparators. |
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47 parser := self parseMethod:source in:aClass. |
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48 parser notNil ifTrue:[ |
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49 "look for variables" |
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50 |
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51 variables := parser methodVars. |
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52 (variables notNil and:[variables includes:string]) ifTrue:[ |
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53 ^ string , ' is a method variable' |
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54 ]. |
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55 variables := parser methodArgs. |
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56 (variables notNil and:[variables includes:string]) ifTrue:[ |
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57 ^ string , ' is a method argument' |
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58 ] |
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59 ]. |
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60 parser isNil ifTrue:[ |
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61 parser := self for:(ReadStream on:source) in:aClass |
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62 ]. |
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63 |
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64 "instvars" |
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65 variables := aClass allInstVarNames. |
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66 (variables notNil and:[variables includes:string]) ifTrue:[ |
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67 "where is it" |
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68 c := aClass. |
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69 [c notNil] whileTrue:[ |
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70 v := c instVarNames. |
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71 (v notNil and:[v includes:string]) ifTrue:[ |
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72 ^ string , ' is an instance variable in ' , c name |
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73 ]. |
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74 c := c superclass |
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75 ]. |
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76 self error:'oops' |
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77 ]. |
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78 |
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79 "class instvars" |
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80 variables := aClass class allInstVarNames. |
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81 (variables notNil and:[variables includes:string]) ifTrue:[ |
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82 "where is it" |
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83 c := aClass. |
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84 [c notNil] whileTrue:[ |
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85 v := c class instVarNames. |
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86 (v notNil and:[v includes:string]) ifTrue:[ |
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87 ^ string , ' is a class instance variable in ' , c name |
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88 ]. |
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89 c := c superclass |
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90 ]. |
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91 self error:'oops' |
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92 ]. |
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93 |
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94 "classvars" |
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95 c := parser inWhichClassIsClassVar:string. |
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96 c notNil ifTrue:[ |
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97 ^ string , ' is a class variable in ' , c name |
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98 ]. |
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99 |
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100 string knownAsSymbol ifTrue:[ |
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101 "globals" |
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102 sym := string asSymbol. |
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103 (Smalltalk includesKey:sym) ifTrue:[ |
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104 (Smalltalk at:sym) isBehavior ifTrue:[ |
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105 ^ string , ' is a global variable. |
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106 |
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107 ' , string , ' is a class in category ' , (Smalltalk at:sym) category , '.' |
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108 ] ifFalse:[ |
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109 ^ string , ' is a global variable. |
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110 |
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111 Its current value is ' , (Smalltalk at:sym) classNameWithArticle , '.' |
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112 ] |
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113 ]. |
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114 |
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115 list := OrderedCollection new. |
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116 "selectors" |
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117 Smalltalk allBehaviorsDo:[:c| |
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118 (c implements:sym) ifTrue:[ |
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119 list add:(c name) |
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120 ]. |
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121 (c class implements:sym) ifTrue:[ |
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122 list add:(c name , 'class') |
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123 ] |
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124 ]. |
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125 count := list size. |
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126 (count ~~ 0) ifTrue:[ |
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127 tmp := ' is a selector implemented in '. |
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128 (count == 1) ifTrue:[ |
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129 ^ string , tmp , (list at:1) , '.' |
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130 ]. |
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131 (count == 2) ifTrue:[ |
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132 ^ string , tmp , (list at:1) , ' and ' , (list at:2) , '.' |
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133 ]. |
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134 (count == 3) ifTrue:[ |
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135 ^ string , tmp , ' |
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136 ' , (list at:1) , ', ' , (list at:2) , ' and ' , (list at:3) , '.' |
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137 ]. |
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138 (count == 4) ifTrue:[ |
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139 ^ string , tmp , ' |
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140 ' , (list at:1) , ', ' , (list at:2) , ', ' , (list at:3), ' and ' , (list at:4) , '.' |
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141 ]. |
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142 |
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143 commonSuperClass := self commonSuperClassOf:list. |
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144 commonSuperClass ~~ Object ifTrue:[ |
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145 ^ string , tmp, count printString , ' subclasses of ' , commonSuperClass name |
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146 ]. |
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147 |
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148 ^ string , tmp , count printString , ' classes.' |
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149 ] |
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150 ]. |
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151 |
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152 "try for some obvious things" |
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153 tmp := self explainPseudoVariable:string in:aClass. |
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154 tmp notNil ifTrue:[ ^ tmp]. |
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155 |
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156 "try syntax ..." |
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157 |
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158 ((string = ':=') or:[string = '_']) ifTrue:[ |
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159 ^ '<variable> := <expression> |
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160 |
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161 := and _ (which is left-arrow in some fonts) mean assignment. |
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162 The variable is bound to (i.e. points to) the value of <expression>.' |
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163 ]. |
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164 |
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165 (string = '^') ifTrue:[ |
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166 ^ '^ <expression> |
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167 |
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168 return the value of <expression> as value from the method. |
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169 A return from within a block exits the method where the block is defined.' |
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170 ]. |
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171 |
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172 (string = ';') ifTrue:[ |
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173 ^ '<expression> ; selector1 ; .... ; selectorN |
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174 |
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175 a cascade expression; evaluate expression, and send messages |
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176 <selector1> ... <selectorN> to the first expressions receiver. |
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177 Returns the value of the last send. The cascade sends may also have arguments.' |
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178 ]. |
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179 |
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180 (string = '|') ifTrue:[ |
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181 ^ '| locals | or: [:arg | statements] |
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182 |
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183 | is used to mark a local variable declaration or separates arguments |
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184 from the statements in a block. Notice, that in a block-argument declaration |
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185 these must be prefixed by a colon character. |
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186 | is also a selector understood by Booleans.' |
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187 ]. |
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188 |
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189 ((string startsWith:'(') or:[string endsWith:')']) ifTrue:[ |
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190 ^ '(<expression>) |
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191 |
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192 expression grouping.' |
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193 ]. |
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194 |
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195 ((string startsWith:'[') or:[string endsWith:']']) ifTrue:[ |
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196 ^ '[arguments | statements] |
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197 |
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198 defines a block. |
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199 Blocks represent pieces of executable code. Definition of a block does |
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200 not evaluate it. The block is evaluated by sending it a value/value: |
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201 message. |
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202 Blocks are often passed as arguments to Booleans (i.e. ifTrue:[...]) or |
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203 collections (i.e. do:[...]).' |
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204 ]. |
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205 |
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206 string knownAsSymbol ifTrue:[ |
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207 ^ string , ' is known as a symbol. |
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208 |
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209 Symbols are unique strings, meaning that there exists |
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210 exactly one instance of a given symbol. Therefore symbols can |
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211 be compared using == (identity compare) instead of = (contents compare).' |
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212 ]. |
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213 |
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214 (string startsWith:'#' ) ifTrue:[ |
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215 (string startsWith:'#(' ) ifTrue:[ |
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216 ^ 'is a constant Array. |
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217 |
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218 The elements of a constant Array must be Number-constants, nil, true or false. |
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219 (notice, that not all smalltalk implementations allow true, false and nil as |
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220 constant-Array elements).' |
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221 ]. |
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222 |
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223 (string startsWith:'#[') ifTrue:[ |
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224 ^ 'is a constant ByteArray. |
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225 |
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226 The elements of a constant ByteArray must be Integer constants in the range |
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227 0 .. 255. |
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228 (notice, that not all smalltalk implementations support constant ByteArrays).' |
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229 ]. |
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230 |
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231 ^ 'is a symbol. |
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232 |
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233 Symbols are unique strings, meaning that there exists |
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234 exactly one instance of a given symbol. Therefore symbols can |
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235 be compared using == (identity compare) instead of = (contents compare).' |
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236 ]. |
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237 |
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238 parser isNil ifTrue:[ |
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239 ^ 'parse error -no explanation' |
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240 ]. |
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241 ^ 'cannot explain this - select individual tokens for an explanation.' |
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242 ! |
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243 |
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244 explainPseudoVariable:string in:aClass |
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245 "return explanation for the pseudoVariables self, super etc." |
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246 |
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247 (string = 'self') ifTrue:[ |
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248 ^ 'self refers to the object which received the message. |
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249 |
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250 In this case, it will be an instance of ' , aClass name , ' |
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251 or one of its subclasses.' |
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252 ]. |
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253 |
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254 (string = 'super') ifTrue:[ |
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255 ^ 'like self, super refers to the object which received the message. |
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256 |
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257 However, when sending a message to super the search for methods |
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258 implementing this message will start in the superclass (' , aClass superclass name , ') |
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259 instead of selfs class.' |
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260 ]. |
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261 |
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262 (string = 'true') ifTrue:[ |
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263 ^ 'true is a pseudo variable (i.e. it is built in). |
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264 |
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265 True represents logical truth. It is the one and only instance of class True.' |
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266 ]. |
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267 |
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268 (string = 'thisContext') ifTrue:[ |
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269 ^ 'thisContext is a pseudo variable (i.e. it is built in). |
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270 |
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271 ThisContext always refers to the context object for the currently executed Method or |
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272 Block (an instance of Context or BlockContext respectively). The calling chain and calling |
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273 selectors can be accessed via thisContext.' |
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274 ]. |
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275 |
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276 (string = 'false') ifTrue:[ |
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277 ^ 'false is a pseudo variable (i.e. it is built in). |
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278 |
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279 False represents logical falseness. It is the one and only instance of class False.' |
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280 ]. |
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281 |
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282 (string = 'nil') ifTrue:[ |
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283 ^ 'nil is a pseudo variable (i.e. it is built in). |
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284 |
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285 Nil is used for unitialized variables (among other uses). |
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286 Nil is the one and only instance of class UndefinedObject.' |
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287 ]. |
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288 ^ nil |
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289 ! |
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290 |
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291 |
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292 commonSuperClassOf:listOfClassNames |
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293 |common found| |
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294 |
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295 listOfClassNames do:[:className | |
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296 |class| |
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297 |
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298 ((className endsWith:'class') and:[className ~= 'Metaclass']) ifTrue:[ |
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299 class := Smalltalk at:(className copyFrom:1 to:(className size - 5)) asSymbol class |
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300 ] ifFalse:[ |
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301 class := Smalltalk at:(className asSymbol). |
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302 ]. |
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303 common isNil ifTrue:[ |
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304 common := class |
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305 ] ifFalse:[ |
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306 (class isSubclassOf:common) ifTrue:[ |
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307 "keep common" |
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308 ] ifFalse:[ |
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309 (common isSubclassOf:class) ifTrue:[ |
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310 common := class |
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311 ] ifFalse:[ |
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312 "walk up, checking" |
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313 found := false. |
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314 common allSuperclassesDo:[:sup | |
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315 (class isSubclassOf:sup) ifTrue:[ |
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316 common := sup |
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317 ] |
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318 ]. |
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319 found ifFalse:[ |
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320 class allSuperclassesDo:[:sup | |
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321 (common isSubclassOf:sup) ifTrue:[ |
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322 common := sup |
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323 ] |
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324 ]. |
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325 ]. |
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326 ] |
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327 ]. |
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328 ]. |
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329 common == Object ifTrue:[^ common] |
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330 ]. |
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331 ^ common |
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332 ! ! |