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4 <TITLE>Homepage of Christian Urban</TITLE> |
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41 |
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42 <B>Links</B><BR> |
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43 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/index.html">Home</A><BR> |
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44 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/publications.html">Publications</A><BR> |
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45 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/teaching.html">Teaching</A><BR> |
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46 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/travelling.html">Recent Talks</A><BR> |
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47 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Nominal/">Nominal Isabelle</A> |
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48 <BR> |
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49 <BR> |
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50 |
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51 <B>Handy Information</B><BR> |
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52 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/logic.html">People in Logic</A><BR> |
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53 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/programming.html">Programming Languages</A><BR> |
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54 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/misc.html">Miscellaneous</A> |
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55 <BR><BR> |
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56 |
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57 <table border="0"> |
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58 <tr> |
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59 <td> |
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60 <A HREF="http://http://www.inf.kcl.ac.uk/staff/urbanc/Nominal/"> |
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61 <IMG SRC="nominal-logo.gif" ALT="" style="border-width: 0px;" align="left"></A> |
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62 </td> |
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63 </tr> |
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64 <tr> |
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65 <td> |
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66 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Cookbook/"> |
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75 <!-- right column --> |
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76 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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77 <A NAME="Home"></A> |
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78 <TABLE> |
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79 <TR> |
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80 <TD WIDTH="75%"> |
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81 <H1>Christian Urban</H1> |
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82 |
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83 <B>E-mail</B> |
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84 christian.urban <I>at</I> kcl ac uk<BR> |
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85 <BR> |
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86 |
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87 <B>Address</B> |
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88 <A HREF="http://www.inf.kcl.ac.uk">Department of Informatics</A>, |
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89 <A HREF="http://www.kcl.ac.uk">King's College London</A>, |
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90 Strand, London WC2R 2LS, UK. My office is S1.27 on the 1st floor of the Strand Building. |
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91 <BR> |
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92 |
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93 </TD> |
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94 <TD align="right" valign="top"> |
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95 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/picture-small.jpg"><IMG ALT="" SRC="picture-small.jpg" align="top"></A> |
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96 </TD> |
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97 </TR> |
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98 </TABLE> |
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99 <p> |
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100 <IMG SRC="new.gif" ALT="" style="" align="left"><A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Cookbook" target="_top">Isabelle Programming Tutorial</A> (draft of a 200-page tutorial on Isabelle programming)<BR><BR> |
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101 </TD> |
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102 </TR> |
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103 |
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104 <TR> |
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105 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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106 <B>Current Position</B> |
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107 I am a lecturer in the Department of Informatics at King's College London. |
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108 This is similar to a position of an assistant professor in other places. In 2011, |
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109 I was also offered a lectureship |
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110 <A HREF="http://www.it.uu.se/" TITLE="Uppsala">here</A>, an associate professorship |
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111 <A HREF="http://www.itu.dk/en/" TITLE="ITU, Copenhagen">here</A>, |
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112 and full professorships |
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113 <A HREF="http://www.ustcsz.edu.cn/kedweb/" TITLE="IAS, Suzhou">here</A> and |
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114 <A HREF="http://202.120.81.220/index.aspx" TITLE="Shanghai">here</A>. |
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115 I thank all people involved for their efforts. |
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116 <P> |
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117 |
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118 <B>Past Positions</B> |
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119 In April 2006, I was awarded an <A HREF="http://en.wikipedia.org/wiki/Emmy_Noether">Emmy-Noether</A> |
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120 <A HREF="http://www.dfg.de/en/research_funding/programmes/individual/emmy_noether/in_brief/index.html">fellowship</A>, which I held at the <A HREF="http://www.in.tum.de/en.html">TU Munich</A> until |
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121 September 2011. |
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122 Between September 2008 and February 2009, I was an invited research scientist in |
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123 the <A HREF="http://www.cs.princeton.edu/">Department of Computer Science</A> in Princeton. |
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124 In 2004/05 I was an Alexander-von-Humboldt fellow in Munich and |
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125 from 2000 until 2004 I was awarded a Research Fellowship in Cambridge. Before that |
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126 I did my PhD in Cambridge funded by two scholarships from the German Academic Exchange |
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127 Service (<A HREF="http://www.daad.de/index.html">DAAD</A>). |
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128 <P> |
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129 |
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130 <B>Skolem Award 2015</B> Together with |
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131 <A HREF="http://www.pps.univ-paris-diderot.fr/~tasson/">Christine Tasson</A>, I was awarded a |
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132 <A HREF="http://www.cadeinc.org/SkolemAward.html">Thoralf Skolem Award</A>, a ten-year |
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133 test-of-time award from CADE, for our |
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134 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Publications/nom-cade-05.ps">paper</A> |
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135 on Nominal Techniques in Isabelle/HOL from 2005. |
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136 <P> |
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137 |
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138 <B>Research Interests</B> theorem provers, verification, programming languages, compilers, |
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139 algorithms, proof theory, type systems, concurrency, lambda calculus, unification, |
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140 regular expressions, computability, complexity, functional and logic programming. |
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141 <P> |
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142 |
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143 <B>Teaching</B> I usually enjoy teaching. At King's my students nominated me for the Teaching |
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144 Excellence Award in |
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145 2012 and 2015, and for the best MSc Project supervisor in 2015. |
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146 In 2014 I received both prizes for Best UG Project Supervisor and for Best |
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147 MSc Project Supervisor in the <A HREF="http://www.kcl.ac.uk/nms/index.aspx">NMS Faculty<A>.<P> |
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148 |
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149 |
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150 <B>Conferences</B> |
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151 UNIF'06 (member of PC), |
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152 <A HREF="http://www.cs.mcgill.ca/~bpientka/lfmtp07">LFMTP'07</A> (member of PC), |
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153 <A HREF="http://http://www.inf.kcl.ac.uk/staff/urbanc/Nominal/activities/lfmtp08/">LFMTP'08</A> (PC co-chair), |
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154 <A HREF="http://www.cis.upenn.edu/~sweirich/wmm/">WMM'08</A> (member of PC), |
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155 <A HREF="http://www.mat.ufmg.br/lsfa2008/">LSFA'08</A> (invited speaker), |
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156 <A HREF="http://www.inf.kcl.ac.uk/staff/maribel/TAASN.html">TAASN'09</A> (member of PC), |
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157 <A HREF="http://lsfa09.cic.unb.br/">LSFA'09</A> (member of PC), |
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158 <A HREF="http://http://www.inf.kcl.ac.uk/staff/urbanc/Nominal/activities/tphols09/idw.html">IDW'09</A> (organiser), |
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159 <A HREF="http://www.seas.upenn.edu/~sweirich/wmm/wmm09.html">WMM'09</A> (PC chair), |
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160 <A HREF="https://http://www.inf.kcl.ac.uk/staff/urbanc/Nominal/activities/tphols09/">TPHOLs'09</A> (PC co-chair), |
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161 <A HREF="http://dream.inf.ed.ac.uk/events/automatheo-2010/">Automatheo'10</A> (member of PC), |
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162 <A HREF="http://www.floc-conference.org/">ITP'10</A> (member of PC), |
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163 <A HREF="http://www.inf.kcl.ac.uk/staff/maribel/UNIF/UNIF.html">UNIF'10</A> (invited speaker), |
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164 <A HREF="http://www.cis.upenn.edu/~bcpierce/wmm/">WMM'10</A> (invited speaker), |
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165 <A HREF="http://http://www.inf.kcl.ac.uk/staff/urbanc/Nominal/activities/idw10/idw.html">IDW'10</A> (co-organiser), |
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166 CPP'11 (member of PC), |
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167 <A HREF="http://www.rdp2011.uns.ac.rs/rta/">RTA'11</A> (member of PC), |
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168 <A HREF="http://lfmtp11.cs.umn.edu">LFMTP'11</A> (member of PC), |
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169 <A HREF="http://www.cs.uwyo.edu/~ruben/itp-2014">ITP'14</A> (member of PC), |
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170 <A HREF="http://www.cicm-conference.org/2015/cicm.php?event=mkm">MKM'15</A> (member of PC), |
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171 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/itp-2015/">ITP'15</A> (PC co-chair) |
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172 <P> |
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173 |
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174 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/itp-2015/">ITP'15</A> took place in Nanjing organised |
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175 by Xingyuan Zhang and me<BR> |
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176 <p> |
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177 |
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178 <B>Current PhD</B> Fahad Ausaf<BR> |
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179 <B>Former RAs</B> Chunhan Wu, <A HREF="http://cl-informatik.uibk.ac.at/users/cek/">Cezary Kaliszyk</A>, |
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180 <A HREF="http://dpt-info.u-strasbg.fr/~narboux/">Julien Narboux</A> |
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181 </TD> |
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182 </TR> |
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183 |
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184 <TR> |
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185 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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186 <B>Nominal Isabelle</B> |
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187 I currently work on Nominal |
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188 <A HREF="http://isabelle.in.tum.de">Isabelle</A> 2. This is joint work with |
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189 <A HREF="http://wwwbroy.in.tum.de/~berghofe/">Dr Stefan Berghofer</A>, |
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190 <A HREF="http://www.lri.fr/~wenzel/">Dr Markus Wenzel</A>, |
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191 <A HREF="http://cl-informatik.uibk.ac.at/users/cek/">Dr Cezary Kaliszyk</A>, |
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192 <A HREF="http://user.it.uu.se/~tjawe125/">Dr Tjark Weber</A> and |
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193 the Isabelle-team in Munich. |
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194 Many of the theoretical ideas originate from the nominal logic project - a wonderful project headed |
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195 by <A HREF="http://www.cl.cam.ac.uk/~amp12/">Prof. Andrew Pitts</A>. |
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196 The aim of my work is to make formal reasoning involving binders as simple as |
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197 on paper and the hope is to lure |
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198 <A HREF="http://alliance.seas.upenn.edu/~plclub/cgi-bin/poplmark/index.php?title=The_POPLmark_Challenge#Vision">masses</A> to automated |
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199 theorem proving. My funding for this work was provided in 2004 and 2005 by a research |
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200 fellowship from the |
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201 <A HREF="http://en.wikipedia.org/wiki/Alexander_von_Humboldt">Alexander-von-Humboldt</A> |
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202 <A HREF="http://www.humboldt-foundation.de/web/home.html">foundation</A>. During this time I was a visitor in the group of |
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203 <A HREF="http://www.mathematik.uni-muenchen.de/~schwicht/">Prof. Helmut Schwichtenberg</A>. |
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204 Since 2006 this work is supported by an |
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205 <A HREF="http://en.wikipedia.org/wiki/Emmy_Noether">Emmy-Noether</A> |
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206 <A HREF="http://www.dfg.de/en/research_funding/programmes/individual/emmy_noether/in_brief/index.html">fellowship</A>. |
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207 There is a <A HREF="http://http://www.inf.kcl.ac.uk/staff/urbanc/Nominal/">webpage</A> and a |
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208 <A HREF="https://mailmanbroy.informatik.tu-muenchen.de/mailman/listinfo/nominal-isabelle">mailing list</A> |
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209 about Nominal Isabelle. It also includes a list of projects that use Nominal Isabelle. |
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210 Users of Nominal Isabelle had their papers appearing at LICS, POPL, FOSSACS, SOS, TPHOLs, CPP, SEFM, |
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211 the Haskell Symposium and |
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212 in the Journal of Automated Reasoning. |
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213 </TD> |
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214 </TR> |
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215 |
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216 <TR> |
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217 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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218 <B>Myhill-Nerode and Regular Expressions</B> |
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219 Out of frustration of having to teach reasoning in theorem provers with worn-out examples like |
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220 fib and even/odd, we implemented a large part of regular language theory in Isabelle/HOL. |
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221 This <A HREF="http://afp.sourceforge.net/devel-entries/Myhill-Nerode.shtml">implementation</A> |
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222 gives rise to much more interesting examples, as shown |
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223 <A HREF="http://www.cs.cmu.edu/~rwh/papers/regexp/jfp.pdf">here</A> and |
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224 <A HREF="http://ropas.snu.ac.kr/~kwang/paper/06-jfp-yi.pdf">here</A>. It turns out that |
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225 formalisations of automata theory are a huge |
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226 <A HREF="https://lists.cam.ac.uk/pipermail/cl-isabelle-users/2005-September/msg00012.html">pain</A> |
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227 in theorem provers, especially in those that are based on HOL. |
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228 We therefore went against the |
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229 <A HREF="http://www.cs.cornell.edu/~kozen/papers/papers_by_year.htm#K97a">mainstream</A> |
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230 and used in our formalisation regular expressions exclusively, |
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231 because they are much more convenient for formal reasoning. The results we |
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232 formalised include: the Myhill-Nerode theorem, the closure of regular languages |
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233 under complementation, finiteness of derivatives of regular expressions and a surprising |
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234 result about Subseq, which according to |
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235 this |
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236 <A HREF="http://blog.computationalcomplexity.org/2006/01/theorem-that-should-be-better-known.html">blog</A> |
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237 should be better known. We also answered a |
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238 <A HREF="http://blog.computationalcomplexity.org/2013/02/proving-dfa-langs-closed-under-concat.html">question</A> from the same blog about |
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239 "proving Reg-exp-langs [being] closed under complementation without using equiv to DFA's"....yes we can! |
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240 This is joint work with Prof. Xingyuan |
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241 Zhang and his student Chunhan Wu from the |
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242 <A HREF="http://www.ust.com.cn/">PLA University of Science and Technology</A> in Nanjing. |
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243 My funding for this work came from the |
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244 <A HREF="http://www.sinogermanscience.org.cn/">Chinese-German Research Centre</A>. |
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245 </TD> |
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246 </TR> |
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247 |
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248 <!-- |
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249 <TR> |
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250 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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251 <B>Priority Inheritance</B> |
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252 In real-time operating systems with processes, resource locking and |
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253 priority scheduling, one faces the problem of indefinite |
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254 <A HREF="http://en.wikipedia.org/wiki/Priority_inversion">priority inversion</A> (processes |
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255 with lower priority block processes with higher priority). If you do not prevent this problem, |
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256 then processes can behave quite erratically, as <A HREF="http://www.nasa.gov">NASA</A> found out the |
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257 <A HREF="http://catless.ncl.ac.uk/Risks/19.54.html#subj6">hard</A> way with their |
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258 <A HREF="http://www.nasa.gov/mission_pages/mars-pathfinder/index.html">Mars Pathfinder mission</A>. |
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259 The priority inheritance protocol is a widely used schedulling algorithm that prevents |
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260 priority inversion. However, the <A HREF="http://dx.doi.org/10.1109/12.57058">original paper</A> |
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261 describing this algorithm contains an incorrect algorithm and a bogus correctness proof |
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262 (this seems to be the only "proof" about priority inheritance in the literature). |
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263 |
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264 We formalised the priority inheritance protocol, including a generalisation |
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265 of the original work. |
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266 |
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267 using the inductive method we learned from |
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268 <A HREF="https://www.cl.cam.ac.uk/~lp15/">Prof. Larry Paulson</A>. |
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269 While the problem with the original algorithm was already known, the incorrect |
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270 specification seems to be still in use |
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271 |
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272 <A HREF="http://mcs.une.edu.au/%7Eiam/Data/threads/node15.html">here</A> |
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273 <A HREF="http://ems2.be/Portals/6/course_docs/OS_pathfinder_failure.ppt"> |
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274 |
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275 This is joint work with Prof. Xingyuan Zhang and his student Chunhan Wu from the |
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276 <A HREF="http://www.ust.com.cn/">PLA University of Science and Technology</A> in Nanjing. |
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277 </TD> |
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278 </TR> |
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279 --> |
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280 |
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281 <TR> |
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282 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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283 <B>Nominal Unification and Alpha-Prolog</B> |
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284 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Unification">Nominal unification</A> is one outcome of |
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285 my involvement in the nominal logic project in Cambridge. Another is the logic programming language |
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286 alpha-Prolog (joint work with <A HREF="http://homepages.inf.ed.ac.uk/jcheney/">Dr James Cheney</A>), |
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287 which uses nominal unification - click for details |
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288 <A HREF="http://homepages.inf.ed.ac.uk/jcheney/programs/aprolog/">here</A>. |
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289 The nominal unification algorithm has been |
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290 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Unification">formally verified</A> in Isabelle. This |
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291 was possible since this unification algorithm is formulated in a simple first-order language |
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292 (unlike other algorithms for higher-order unification). |
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293 <A HREF="http://www.cs.indiana.edu/~dfried/">Prof. Daniel Friedman</A> and his group use nominal |
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294 unification in their alpha-Kanren system implemented in Scheme. |
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295 <A HREF="http://www.inf.kcl.ac.uk/staff/maribel/">Prof. Maribel Fernandez</A> and her student |
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296 improved the nominal unification algorithm to be quadratic. |
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297 My funding for this work was provided through a research fellowship from |
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298 <A HREF="http://www.corpus.cam.ac.uk">Corpus Christi College</A>, Cambridge. |
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299 </TD> |
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300 </TR> |
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301 |
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302 <TR> |
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303 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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304 <B>Classical Logic</B> |
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305 I was Ph.D. student in the University of Cambridge |
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306 <A HREF="http://www.cl.cam.ac.uk">Computer Laboratory</A> |
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307 and for three years |
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308 called Gonville and Caius College my home. I was very lucky to have |
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309 <A HREF="https://labs.oracle.com/pls/apex/f?p=labs:bio:0:2044">Dr Gavin Bierman</A> |
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310 as supervisor. My research in Cambridge was also very much influenced by |
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311 <A HREF="http://www.dpmms.cam.ac.uk/~martin/">Prof. Martin Hyland</A>. |
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312 Some details on my thesis "Classical Logic and Computation" are |
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313 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/PhD/index.html">elsewhere</A>, including |
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314 a <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Cut/cutapplet.html">Java Applet</A> that |
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315 'visualises' some of the results from the thesis. I completed the writing of |
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316 the thesis in <A HREF="http://iml.univ-mrs.fr/ldp/">Marseille</A> in the group of |
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317 <A HREF="http://iml.univ-mrs.fr/~girard/">Prof. Jean-Yves Girard</A>. My study in |
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318 Cambridge was funded by two <A HREF="http://www.daad.de/index.html">scholarships</a> |
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319 from the German government; my year in Marseille by a TMR-fellowship from the EU. |
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320 My PhD was also one starting point for the EPSRC Project on the Semantics of Classical |
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321 Proofs. The strong normalisation result in the PhD has been used in 2007 by |
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322 <A HREF="http://www.loria.fr/~ckirchne/hot.html">Prof. Claude Kirchner</A> and his |
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323 students for proving consistency of their superdeduction system lemuridae. |
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324 </TD> |
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325 </TR> |
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326 |
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327 |
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328 |
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329 <TR> |
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330 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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331 <B>Forum</B> |
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332 I implemented Forum, a programming language based on classical linear logic, |
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333 as my M.Phil. thesis. This was joint work with |
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334 <A HREF="http://www.cs.st-andrews.ac.uk/~rd/">Dr Roy Dyckhoff</A>. |
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335 Details can be found |
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336 <A HREF="http://www.cs.st-andrews.ac.uk/~rd/logic/nonmac/">here</A> and |
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337 <A HREF="http://www.lix.polytechnique.fr/Labo/Dale.Miller/forum/">here</A>. During my |
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338 M.Phil study I spent one month in Philadelphia invited by |
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339 <A HREF="http://www.lix.polytechnique.fr/~dale/">Prof. Dale Miller</A>. |
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340 </TD> |
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341 </TR> |
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342 |
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343 <TR> |
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344 <TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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345 <B>G4ip</B> An implementation of G4ip using the imperative language Pizza can be found |
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346 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Prover/index.html">here</A>. |
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347 <A HREF="http://pizzacompiler.sourceforge.net">Pizza</A>, written around 1996, is a conservative |
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348 extension of Java and a precursor of Scala. My implementation illustrates the technique of |
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349 success continuations in proof search. |
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350 </TD> |
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351 </TR> |
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352 |
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353 |
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354 </TABLE> |
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355 <P> |
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