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5 <title>λδ home page</title>
6 <meta content="Ferruccio Guidi" name="author">
7 <meta content="The formal system λδ" name="description">
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15 <h1>The Formal System λδ (\lambda\delta)<br>
17 <h2>Towards the unification of terms, types, environments and contexts</h2>
18 <img style="width: 95%; height: 4px;" alt="[Separator]"
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25 <td style="vertical-align: top;">
27 <li><a href="index.html">Foreword</a></li>
33 <li><a href="documentation.html">Papers</a></li>
36 <li><a href="implementation.html">Resources</a><br>
40 <td style="vertical-align: top; text-align: left;">
41 <h3 style="text-align: right;">News <img
42 style="width: 37px; height: 37px;" alt="[Butterfly]" title="Butterfly"
43 src="images/b5.png"></h3>
45 <li><span style="font-weight: bold;">June 2014.</span> <a
46 href="documentation.html#ldt8">First communication on λδ version 2.</a><br>
47 <span style="font-weight: bold;"></span></li>
50 <li><span style="font-weight: bold;">December 2012.</span> The
51 character "_" is removed from the denomination "lambda_delta". </li>
55 <li>The denomination "\lambda\delta" is used in λδ-related
57 <li>The denomination "lambdadelta" is used in λδ-related
59 <li>Permanent λδ URL acquired: <a
60 href="http://lambdadelta.info/">http://lambdadelta.info/</a>
61 (pointing at this site). </li>
65 <li><span style="font-weight: bold;">September 2011.</span> The
66 denomination "lambda-delta" changes to "lambda_delta".
68 <li>The character "-" is reserved in λδ textual syntax
69 (recognized by <span style="font-style: italic;">Helena 0.8.1</span>).
71 <li>Eventually, the occurrences of the character "-" will
72 be replaced by "_" in all λδ-related identifiers.</li>
73 <li>In particular, this refactoring involves file names and
79 <li><span style="font-weight: bold;">April 2011.</span> The
80 specification of λδ version 2 and related topics is restarted in <a
81 href="http://matita.cs.unibo.it/">Matita 0.5</a>.
83 <li><a href="apps_2.html">Here</a> is a page about the
84 topics related to the specification (Applications).</li>
85 <li><a href="basic_2.html">Here</a> is a page about the
86 specification (Core). </li>
87 <li><a href="ground_2.html">Here</a> is a page about the
88 background of the specification (Ground).</li>
93 <li><span style="font-weight: bold;">December 2010.</span>
94 Transient λδ URL acquired: http://lambda-delta.info/
95 (expires on December 2012). <br>
96 <span style="font-weight: bold;"></span></li>
99 <li><span style="font-weight: bold;">November 2010.</span> <span
100 style="font-style: italic;">Helena 0.8.1</span> is released. <br>
104 <li><span style="font-weight: bold;">September 2009.</span> <span
105 style="font-style: italic;">Helena 0.8.0</span> is released and the <a
106 href="implementation.html#lddl">λδ Digital Library</a> is started.<br>
107 <span style="font-weight: bold;"></span></li>
110 <li><span style="font-weight: bold;">June 2009.</span> <span
111 style="font-style: italic;">Helena</span>, a <a
112 href="implementation.html#helena">validator for λδ version 2</a>, is
113 available as a part of the <a href="http://helm.cs.unibo.it/">HELM</a>
117 <span style="font-weight: bold;"></span>
119 <li><span style="font-weight: bold;">September 2008.</span>
120 This site is online.<br>
123 <span style="font-weight: bold;"></span>
125 <li><span style="font-weight: bold;">July 2008.</span> <a
126 href="documentation.html#ldp5">First journal paper on λδ</a> accepted
127 for publication.</li>
130 <li><span style="font-weight: bold;">July 2008.</span> First <a
131 href="http://helm.cs.unibo.it/procedural/">procedural reconstruction</a>
132 for <a href="http://matita.cs.unibo.it/">Matita 0.5</a> of the <a
133 href="implementation.html#ldp1">λδ proof scripts for Coq 7.3.1</a>.<br>
137 <li><span style="font-weight: bold;">June 2008.</span> The <a
138 href="implementation.html#static">HTML pages of the specification of
139 λδ version 1 for Matita 0.5</a> are online.<br>
140 <span style="font-weight: bold;"></span></li>
143 <li><span style="font-weight: bold;">May 2008.</span> The
144 specification of λδ version 1 is dismissed.<br>
145 <span style="font-weight: bold;"></span></li>
148 <li><span style="font-weight: bold;">March 2008.</span> The
149 specification of λδ version 2 is started with Coq 7.3.1 (false start). </li>
152 <li>native type assignment with new rules for application: <span
153 style="font-style: italic;">nty</span> (it replaces <span
154 style="font-style: italic;">ty3</span>);<br>
156 <li>parallel conversion on focalized terms: <span
157 style="font-style: italic;">fpcs</span> (it replaces <span
158 style="font-style: italic;"></span><span style="font-style: italic;">pc3</span>);
161 <li>new weak parallel reduction on environments: <span
162 style="font-style: italic;">wcpr</span> <span
163 style="font-style: italic;"></span>(it is based on <span
164 style="font-style: italic;">fpr</span> and replaces <span
165 style="font-style: italic;">wcpr0</span>); <br>
167 <li>parallel reduction on focalized terms: <span
168 style="font-style: italic;">fpr</span> and <span
169 style="font-style: italic;">fprs</span> (they replace <span
170 style="font-style: italic;"></span><span style="font-style: italic;"></span><span
171 style="font-style: italic;">pr2</span>, <span
172 style="font-style: italic;">pr3</span>); <br>
176 <li>new thinning relation: <span
177 style="font-style: italic;">drop</span>
178 (it replaces the old <span style="font-style: italic;">drop</span>, <span
179 style="font-style: italic;">clear</span>, <span
180 style="font-style: italic;">getl</span>, <span
181 style="font-style: italic;">cimp</span>, <span
182 style="font-style: italic;">drop1</span>);</li>
183 <li>new shift function: <span style="font-style: italic;">shift</span>:
187 <span style="font-style: italic;">app1</span>);</li>
188 <li>new length function for environments: <span
189 style="font-style: italic;">clen</span>;<br>
191 <li>new relocation function: <span
192 style="font-style: italic;">lift</span> (it replaces old <span
193 style="font-style: italic;">lift</span>, <span
194 style="font-style: italic;">lift1</span>);<br>
196 <li>new term structure with polarity indicators and no
197 distinction between binding and flat items;</li>
198 <li>new general theory of relocation (comprises new
199 relocation functions: <span style="font-style: italic;">s</span>, <span
200 style="font-style: italic;">r</span>);</li>
201 <li>we removed context-free reduction and conversion (<span
202 style="font-style: italic;">pr0</span>, <span
203 style="font-style: italic;">pr1</span>, <span
204 style="font-style: italic;">pc1</span>);<br>
206 <li>we removed greedy substitution (<span
207 style="font-style: italic;"></span><span style="font-style: italic;">csubst0</span>,
208 <span style="font-style: italic;">csubst1</span>, <span
209 style="font-style: italic;">fsubst0</span>, <span
210 style="font-style: italic;">subst0</span>, <span
211 style="font-style: italic;">subst1</span>);<br>
213 <li>we removed level indicators on environments (<span
214 style="font-style: italic;">cbk</span>).</li>
218 <li><span style="font-weight: bold;">September 2007.</span> The
219 <a href="implementation.html#dynamic">specification of λδ
220 version 1 for Matita 0.4</a> is online.</li>
223 <li><span style="font-weight: bold;">November 2006.</span> <a
224 href="documentation.html#ldp3">λδ version 1</a> is released.</li>
227 <li><span style="font-weight: bold;">December 2005.</span> <a
228 href="documentation.html#ldt1">First communication on λδ</a>.<br>
232 <li><span style="font-weight: bold;">May 2004.</span> The <a
233 href="implementation.html#ldp1">specification of λδ version 1</a> is
234 started with Coq 7.3.1.<br>
237 <h3 style="text-align: right;">Visibility <img
238 style="width: 37px; height: 37px;" alt="[Butterfly]" title="Butterfly"
239 src="images/b4.png"></h3>
241 <li><span style="font-weight: bold;">June 2014.</span> The <a
242 href="http://www.google.com/">Google</a> search for <span
243 style="color: rgb(255, 0, 0);">formal system lambda delta</span> gives
244 5 resources about λδ in the first 6 results.<br>
248 <li><span style="font-weight: bold;">June 2014.</span> The <a
249 href="http://www.yahoo.com/">Yahoo</a> search <span
250 style="color: rgb(255, 0, 0);">formal system lambda delta</span> gives
251 4 resources about λδ in the first 5 results.</li>
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272 Last update 2014-06-19 by <a href="http://www.cs.unibo.it/%7Efguidi/">Ferruccio