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137 | | -<div id="content"> |
138 | | - <article> |
139 | | - <h1>1 Introduction</h1> |
140 | | - |
141 | | -<h2>1.5 The LFE REPL</h2> |
142 | | - |
143 | | -<h3>1.5.1 Using the REPL</h3> |
144 | | - |
145 | | -<p>We covered basic REPL usage in the |
146 | | -<a href="http://lfe.gitbooks.io/quick-start/content/index.html">quick start</a>. |
147 | | -We'll provide some information about the REPL in the document you are currently |
148 | | -reading :-)</p> |
149 | | - |
150 | | -<h4>1.5.1.1 Starting the REPL</h4> |
151 | | - |
152 | | -<p>If you <em>don't</em> have LFE installed system-wide, you need to tell it (Erlang, |
153 | | -really) where the LFE <code>.beam</code> files are. Here are the three ways to start |
154 | | -up LFE in this case. The easiest is <code>lfetool</code>:</p> |
155 | | -<div class="highlight"><pre><code class="language-bash" data-lang="bash"> $ lfetool repl lfe |
156 | | -</code></pre></div> |
157 | | -<p>If you're project was built with <code>lfetool</code>, then you'll have a make target |
158 | | -called <code>shell</code>; calling this will first compile your source files and then |
159 | | -call out to <code>lfetool</code>. Due to the compiling, this is a little slower way to |
160 | | -start the REPL (though better for debugging!):</p> |
161 | | -<div class="highlight"><pre><code class="language-bash" data-lang="bash"> $ make repl |
162 | | -</code></pre></div> |
163 | | -<p>The nice thing about both of these is that they automatically add your |
164 | | -dependencies to <code>ERL_LIBS</code> so you have access to everything you need in the |
165 | | -REPL itself.</p> |
166 | | - |
167 | | -<p>Here are some more ways to start the REPL that don't take care of these niceties |
168 | | -for you:</p> |
169 | | -<div class="highlight"><pre><code class="language-bash" data-lang="bash"> $ ./bin/lfe -pa ./ebin |
170 | | - LFE Shell V5.10.4 <span class="o">(</span>abort with ^G<span class="o">)</span> |
171 | | - > |
172 | | -</code></pre></div><div class="highlight"><pre><code class="language-bash" data-lang="bash"> $ erl -user lfe_boot -pa /path/to/lfe/ebin |
173 | | - LFE Shell V5.10.4 <span class="o">(</span>abort with ^G<span class="o">)</span> |
174 | | - > |
175 | | -</code></pre></div> |
176 | | -<p>You can also start an LFE REPL from the Erlang shell. First hop into <code>erl</code>:</p> |
177 | | -<div class="highlight"><pre><code class="language-bash" data-lang="bash"> $ erl -pa /path/to/lfe/ebin |
178 | | - Eshell V5.10.4 <span class="o">(</span>abort with ^G<span class="o">)</span> |
179 | | - 1> |
180 | | -</code></pre></div> |
181 | | -<p>then fire up LFE:</p> |
182 | | -<div class="highlight"><pre><code class="language-erlang" data-lang="erlang"> <span class="mi">1</span><span class="o">></span> <span class="nn">lfe_shell</span><span class="p">:</span><span class="nf">server</span><span class="p">().</span> |
183 | | - <span class="nv">LFE</span> <span class="nv">Shell</span> <span class="nv">V5</span><span class="p">.</span><span class="mi">10</span><span class="p">.</span><span class="mi">4</span> <span class="p">(</span><span class="n">abort</span> <span class="n">with</span> <span class="err">^</span><span class="nv">G</span><span class="p">)</span> |
184 | | - <span class="o">></span> |
185 | | -</code></pre></div> |
186 | | -<p>If you do have LFE installed system-wide, then starting the shell can be done in |
187 | | -the ways listed below.</p> |
188 | | -<div class="highlight"><pre><code class="language-bash" data-lang="bash"> $ lfe |
189 | | -</code></pre></div> |
190 | | -<p>You can also start the LFE REPL by passing options directly to <code>erl</code>. |
191 | | -Again, assuming that you have LFE installed system-wide, from any directory you |
192 | | -may do this:</p> |
193 | | -<div class="highlight"><pre><code class="language-bash" data-lang="bash"> $ erl -user lfe_boot |
194 | | -</code></pre></div> |
195 | | -<p>Also, if you happen to be running an Erlang shell already, you can start the |
196 | | -LFE REPL with the following:</p> |
197 | | -<div class="highlight"><pre><code class="language-erlang" data-lang="erlang"><span class="mi">14</span><span class="o">></span> <span class="nn">lfe_shell</span><span class="p">:</span><span class="nf">server</span><span class="p">().</span> |
198 | | -<span class="nv">LFE</span> <span class="nv">Shell</span> <span class="nv">V5</span><span class="p">.</span><span class="mi">9</span><span class="p">.</span><span class="mi">3</span><span class="p">.</span><span class="mi">1</span> <span class="p">(</span><span class="n">abort</span> <span class="n">with</span> <span class="err">^</span><span class="nv">G</span><span class="p">)</span> |
199 | | -<span class="o">></span> |
200 | | -</code></pre></div> |
201 | | -<h4>1.5.1.2 Running Commands</h4> |
202 | | - |
203 | | -<p>Once you're in the REPL, it's just a matter of entering code:</p> |
204 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nb">+</span> <span class="mf">1.5</span> <span class="mi">3</span> <span class="mi">4</span> <span class="mi">5</span> <span class="mi">6</span> <span class="mi">7</span><span class="p">)</span> |
205 | | -<span class="mi">28</span> |
206 | | -<span class="nb">></span> |
207 | | -</code></pre></div> |
208 | | -<p>Unlike the Erlang shell, the LFE REPL supports defining functions:</p> |
209 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nb">defun</span> <span class="nb">exp</span> <span class="p">(</span><span class="nv">x</span> <span class="nv">y</span><span class="p">)</span> |
210 | | - <span class="p">(</span><span class="nv">trunc</span> <span class="p">(</span><span class="nv">math:pow</span> <span class="nv">x</span> <span class="nv">y</span><span class="p">)))</span> |
211 | | -<span class="nb">exp</span> |
212 | | -<span class="nb">></span> |
213 | | -</code></pre></div> |
214 | | -<p>Let's put that <code>exp</code> to use:</p> |
215 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nb">exp</span> <span class="mi">2</span> <span class="mi">6</span><span class="p">)</span> |
216 | | -<span class="mi">64</span> |
217 | | -<span class="nb">></span> |
218 | | -</code></pre></div> |
219 | | -<p>You could take the <code>lambda</code> route too:</p> |
220 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nb">set</span> <span class="nb">exp</span> |
221 | | - <span class="p">(</span><span class="k">lambda</span> <span class="p">(</span><span class="nv">x</span> <span class="nv">y</span><span class="p">)</span> |
222 | | - <span class="p">(</span><span class="nv">trunc</span> <span class="p">(</span><span class="nv">math:pow</span> <span class="nv">x</span> <span class="nv">y</span><span class="p">))))</span> |
223 | | -<span class="err">#</span><span class="nv">Fun<lfe_eval.15.132627770></span> |
224 | | -<span class="nb">></span> |
225 | | -</code></pre></div> |
226 | | -<p>And, if you want to get nuts:</p> |
227 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nv">lists:map</span> |
228 | | - <span class="p">(</span><span class="k">lambda</span> <span class="p">(</span><span class="nv">z</span><span class="p">)</span> |
229 | | - <span class="p">(</span><span class="nb">funcall</span> <span class="nb">exp</span> <span class="p">(</span><span class="nb">car</span> <span class="nv">z</span><span class="p">)</span> <span class="p">(</span><span class="nb">cadr</span> <span class="nv">z</span><span class="p">)))</span> |
230 | | - <span class="p">(</span><span class="nb">list</span> <span class="p">(</span><span class="nb">list</span> <span class="mf">1.5</span> <span class="mi">0</span><span class="p">)</span> <span class="p">(</span><span class="nb">list</span> <span class="mi">3</span> <span class="mi">4</span><span class="p">)</span> <span class="p">(</span><span class="nb">list</span> <span class="mi">5</span> <span class="mi">6</span><span class="p">)))</span> |
231 | | -<span class="p">(</span><span class="mi">1</span> <span class="mi">81</span> <span class="mi">15625</span><span class="p">)</span> |
232 | | -<span class="nb">></span> |
233 | | -</code></pre></div> |
234 | | -<h4>1.5.1.3 Quitting the REPL</h4> |
235 | | - |
236 | | -<p>Just as there are multiple ways in which you can start the REPL, there are a |
237 | | -couple ways you can leave it. You can jump into the JCL from the LFE prompt by |
238 | | -hitting ^g and then entering <code>q</code>:</p> |
239 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="nv">^g</span> |
240 | | -<span class="nv">User</span> <span class="nv">switch</span> <span class="nv">command</span> |
241 | | - <span class="nv">--></span> <span class="nv">q</span> |
242 | | -<span class="nv">$</span> |
243 | | -</code></pre></div> |
244 | | -<p>or you can call the Erlang shell's quit function:</p> |
245 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nv">c:q</span><span class="p">)</span> |
246 | | -<span class="nv">ok</span> |
247 | | -<span class="nb">></span> |
248 | | -<span class="nv">$</span> |
249 | | -</code></pre></div> |
250 | | -<p>Or simplest of all, the LFE <code>exit</code> command:</p> |
251 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nv">exit</span><span class="p">)</span> |
252 | | -<span class="nv">ok</span> |
253 | | -<span class="nb">></span> |
254 | | -<span class="nv">$</span> |
255 | | -</code></pre></div> |
256 | | -<h3>1.5.2 Special Functions</h3> |
257 | | - |
258 | | -<p>There are some functions specially defined in LFE for use from the REPL. |
259 | | -These are listed below with information about their use.</p> |
260 | | - |
261 | | -<ul> |
262 | | -<li><p><code>(c File [Options])</code> - Compile and load an LFE file. Assumes default |
263 | | -extension <code>.lfe</code>.</p></li> |
264 | | -<li><p><code>(l Module ...)</code> - Load modules.</p></li> |
265 | | -<li><p><code>(m Module ...)</code> - Print out module information, if no modules are given |
266 | | -then print information about all modules.</p></li> |
267 | | -<li><p><code>(ec File [Options])</code> - Compile and load an Erlang file.</p></li> |
268 | | -<li><p><code>(slurp File)</code> - Slurp in a source LFE file and makes all functions and |
269 | | -macros defined in the file available in the shell. Only one file can be |
270 | | -slurped at a time and slurping a new file removes all data about the previous |
271 | | -one.</p></li> |
272 | | -<li><p><code>(unslurp)</code> - Remove all function and macro definitions except the |
273 | | -default ones.</p></li> |
274 | | -<li><p><code>(set Pattern Expr)</code> - Evaluate Expr and match the result with Pattern |
275 | | -binding variables in it. These variables can then be used in the shell and |
276 | | -also rebound in another set.</p></li> |
277 | | -<li><p><code>(c:command-arg ...)</code> - All the commands in the Erlang shell's |
278 | | -<a href="http://www.erlang.org/doc/man/c.html">Command Interface Module</a> |
279 | | -can be reached in this way.</p></li> |
280 | | -</ul> |
281 | | - |
282 | | -<h3>1.5.3 Special Variables</h3> |
283 | | - |
284 | | -<p>LFE also provides some convenience variables similar to what Lisp |
285 | | -has defined for |
286 | | -<a href="http://www.lispworks.com/documentation/HyperSpec/Body/v_pl_plp.htm"> +, ++, +++</a>, |
287 | | -<a href="http://www.lispworks.com/documentation/HyperSpec/Body/v__stst_.htm"><em>, *</em>, ***</a>, |
288 | | -and |
289 | | -<a href="http://www.lispworks.com/documentation/HyperSpec/Body/v__.htm">-</a>. |
290 | | -Additionally, LFE also provides the <code>$ENV</code> variable.</p> |
291 | | - |
292 | | -<ul> |
293 | | -<li><code>+/++/+++</code> - The three previous expressions input.</li> |
294 | | -<li><code>*/**/***</code> - The values of the previous 3 expressions.</li> |
295 | | -<li><code>-</code> - The current expression input.</li> |
296 | | -<li><code>$ENV</code> - The current environment (accessible in the REPL as well as in |
297 | | -macros).</li> |
298 | | -</ul> |
299 | | - |
300 | | -<p>These probably warrant some examples.</p> |
301 | | - |
302 | | -<p>Let's say you had just entered the following in the REPL:</p> |
303 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nb">+</span> <span class="mf">1.5</span> <span class="mf">1.5</span><span class="p">)</span> |
304 | | -<span class="mi">3</span> |
305 | | -<span class="nb">></span> <span class="p">(</span><span class="nv">c:memory</span><span class="p">)</span> |
306 | | -<span class="p">(</span><span class="o">#(</span><span class="nv">total</span> <span class="mi">10026672</span><span class="p">)</span> |
307 | | - <span class="o">#(</span><span class="nv">processes</span> <span class="mi">1656528</span><span class="p">)</span> |
308 | | - <span class="o">#(</span><span class="nv">processes_used</span> <span class="mi">1656528</span><span class="p">)</span> |
309 | | - <span class="o">#(</span><span class="nv">system</span> <span class="mi">8370144</span><span class="p">)</span> |
310 | | - <span class="o">#(</span><span class="nb">atom</span> <span class="mi">153321</span><span class="p">)</span> |
311 | | - <span class="o">#(</span><span class="nv">atom_used</span> <span class="mi">147399</span><span class="p">)</span> |
312 | | - <span class="o">#(</span><span class="nv">binary</span> <span class="mi">1338560</span><span class="p">)</span> |
313 | | - <span class="o">#(</span><span class="nv">code</span> <span class="mi">3255239</span><span class="p">)</span> |
314 | | - <span class="o">#(</span><span class="nv">ets</span> <span class="mi">290544</span><span class="p">))</span> |
315 | | -<span class="nb">></span> <span class="p">(</span><span class="nb">set</span> <span class="nv">my-func</span> <span class="p">(</span><span class="k">lambda</span> <span class="p">()</span> <span class="p">(</span><span class="nv">io:format</span> <span class="s">"Hello, Zaphod!~n"</span><span class="p">)))</span> |
316 | | -<span class="err">#</span><span class="nv">Fun<lfe_eval.23.86468545></span> |
317 | | -<span class="nb">></span> |
318 | | -</code></pre></div> |
319 | | -<p>Then you can get the previous expressions you input with the following |
320 | | -commands:</p> |
321 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="nv">+++</span> |
322 | | -<span class="p">(</span><span class="nb">+</span> <span class="mf">1.5</span> <span class="mf">1.5</span><span class="p">)</span> |
323 | | -<span class="nb">></span> <span class="nv">+++</span> |
324 | | -<span class="p">(</span><span class="nv">c:memory</span><span class="p">)</span> |
325 | | -<span class="nb">></span> <span class="nv">+++</span> |
326 | | -<span class="p">(</span><span class="nb">set</span> <span class="nv">my-func</span> <span class="p">(</span><span class="k">lambda</span> <span class="p">()</span> <span class="p">(</span><span class="nv">io:format</span> <span class="s">"Hello, Zaphod!~n"</span><span class="p">)))</span> |
327 | | -<span class="nb">></span> <span class="nv">++</span> |
328 | | -<span class="nv">+++</span> |
329 | | -<span class="nb">></span> <span class="nb">+</span> |
330 | | -<span class="nv">++</span> |
331 | | -<span class="nb">></span> |
332 | | -</code></pre></div> |
333 | | -<p>Most of us will actually use the arrow keys, thanks to the <code>readline</code> |
334 | | -library. However, the classic, pre-<code>readline</code> approach is still available, |
335 | | -should you choose to use it.</p> |
336 | | - |
337 | | -<p>Similarly, you can get the results returned by using the variabels from the |
338 | | -second bullet item. If you're following along in the REPL, go ahead and |
339 | | -re-enter the commands we typed above to reset the last three items in your |
340 | | -command history. Then do the following:</p> |
341 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="vg">***</span> |
342 | | -<span class="mi">3</span> |
343 | | -<span class="nb">></span> <span class="vg">***</span> |
344 | | -<span class="p">(</span><span class="o">#(</span><span class="nv">total</span> <span class="mi">9976496</span><span class="p">)</span> |
345 | | - <span class="o">#(</span><span class="nv">processes</span> <span class="mi">1606688</span><span class="p">)</span> |
346 | | - <span class="o">#(</span><span class="nv">processes_used</span> <span class="mi">1606688</span><span class="p">)</span> |
347 | | - <span class="o">#(</span><span class="nv">system</span> <span class="mi">8369808</span><span class="p">)</span> |
348 | | - <span class="o">#(</span><span class="nb">atom</span> <span class="mi">153321</span><span class="p">)</span> |
349 | | - <span class="o">#(</span><span class="nv">atom_used</span> <span class="mi">147399</span><span class="p">)</span> |
350 | | - <span class="o">#(</span><span class="nv">binary</span> <span class="mi">1338096</span><span class="p">)</span> |
351 | | - <span class="o">#(</span><span class="nv">code</span> <span class="mi">3255239</span><span class="p">)</span> |
352 | | - <span class="o">#(</span><span class="nv">ets</span> <span class="mi">290544</span><span class="p">))</span> |
353 | | -<span class="nb">></span> <span class="vg">***</span> |
354 | | -<span class="err">#</span><span class="nv">Fun<lfe_eval.23.86468545></span> |
355 | | -<span class="nb">></span> <span class="p">(</span><span class="nb">funcall</span> <span class="nb">*</span><span class="p">)</span> |
356 | | -<span class="nv">Hello,</span> <span class="nv">Zaphod!</span> |
357 | | -<span class="nv">ok</span> |
358 | | -<span class="nb">></span> |
359 | | -</code></pre></div> |
360 | | -<p>There's another, called the "dash" varibale. It is bound to the actual |
361 | | -expression that is currently being evaluated. Here's an example of this being |
362 | | -used:</p> |
363 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nv">io:format</span> <span class="s">"Evaluating the expression '~p' ...~n"</span> <span class="p">(</span><span class="nb">list</span> <span class="nb">-</span><span class="p">))</span> |
364 | | -<span class="nv">Evaluating</span> <span class="k">the</span> <span class="nv">expression</span> <span class="ss">'[</span><span class="o">'</span><span class="err">:</span><span class="ss">',io,format,</span> |
365 | | - <span class="nv">[quote,</span><span class="s">"Evaluating the expression '~p' ...~n"</span><span class="nv">],</span> |
366 | | - <span class="nv">[list,</span><span class="ss">'-']]</span><span class="o">'</span> <span class="o">...</span> |
367 | | -<span class="nv">ok</span> |
368 | | -<span class="nb">></span> |
369 | | -</code></pre></div> |
370 | | -<p>We've saved one of the more archane special variables to last: <code>$ENV</code>. |
371 | | -When you first start up a shell, the <code>$ENV</code> variable holds pristine state |
372 | | -data:</p> |
373 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="nv">$ENV</span> |
374 | | -<span class="o">#(</span><span class="nv">env</span> |
375 | | -<span class="o">...</span> |
376 | | -<span class="nb">></span> |
377 | | -</code></pre></div> |
378 | | -<p>We can define a few variables and then check them out with another display of |
379 | | -the environment:</p> |
380 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nb">set</span> <span class="nv">my-var</span> <span class="mi">42</span><span class="p">)</span> |
381 | | -<span class="mi">42</span> |
382 | | -<span class="nb">></span> <span class="nv">$ENV</span> |
383 | | -<span class="o">#(</span><span class="nv">env</span> |
384 | | -<span class="o">...</span> |
385 | | - <span class="o">#(</span><span class="nv">my-var</span> <span class="mi">42</span><span class="p">)</span> |
386 | | -<span class="o">...</span> |
387 | | -</code></pre></div> |
388 | | -<p>If you <code>slurp</code> a file in the REPL, your environment will be updated with all |
389 | | -the definitions in that file:</p> |
390 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nv">slurp</span> <span class="s">"../lfe/examples/joes-fav.lfe"</span><span class="p">)</span> |
391 | | -<span class="o">#(</span><span class="nv">ok</span> <span class="nv">joes-fav</span><span class="p">)</span> |
392 | | -<span class="nb">></span> <span class="nv">$ENV</span> |
393 | | -<span class="o">...</span> |
394 | | - <span class="p">(</span><span class="o">#(</span><span class="nv">MODULE</span> <span class="o">#(</span><span class="nv">macro</span> <span class="p">(</span><span class="nv">match-lambda</span> <span class="p">(((</span><span class="nb">list</span><span class="p">)</span> <span class="nv">$ENV</span><span class="p">)</span> <span class="o">`</span><span class="ss">'joes-fav</span><span class="p">))))</span> |
395 | | -<span class="o">...</span> |
396 | | - <span class="o">#(</span><span class="nv">run-it</span> |
397 | | -<span class="o">...</span> |
398 | | - <span class="o">#(</span><span class="nv">universal-server</span> |
399 | | -<span class="o">...</span> |
400 | | -</code></pre></div> |
401 | | -<p>There is, as you might have guessed, much more to that ellided output (for that |
402 | | -particular example, nearly all the rest of it is macro definitions).</p> |
403 | | - |
404 | | -<p>Making use of <code>$ENV</code> can be very helpful when debugging include files, |
405 | | -loading Erlang header files, or when creating macros. Furthermore, when spending |
406 | | -a great deal of time in the REPL prototyping code for a project, it can be |
407 | | -quite useful to refresh one's memory as to what functions and variables are |
408 | | -currently available in <code>$ENV</code>.</p> |
409 | | - |
410 | | -<p>Looking at the output for <code>$ENV</code> can be a bit overwhelming, however. As you |
411 | | -might imagine, there is an easy answer to this: filter it! The following makes |
412 | | -use of the Erlang <code>lists</code> module as well as patterns in an anonymous |
413 | | -function, both of which will be covered in more detail later. This will |
414 | | -prevent most nested variables from being displayed:</p> |
415 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nb">defun</span> <span class="nv">filter-env</span> <span class="p">(</span><span class="nv">env</span><span class="p">)</span> |
416 | | - <span class="p">(</span><span class="nv">lists:foreach</span> |
417 | | - <span class="p">(</span><span class="k">lambda</span> <span class="p">(</span><span class="nv">section</span><span class="p">)</span> |
418 | | - <span class="p">(</span><span class="nv">lists:foreach</span> |
419 | | - <span class="p">(</span><span class="nv">match-lambda</span> |
420 | | - <span class="p">((</span><span class="o">`#(</span><span class="nb">*</span> <span class="o">,</span><span class="nv">_</span><span class="p">)))</span> |
421 | | - <span class="p">((</span><span class="o">`#(</span><span class="nv">**</span> <span class="o">,</span><span class="nv">_</span><span class="p">)))</span> |
422 | | - <span class="p">((</span><span class="o">`#(</span><span class="vg">***</span> <span class="o">,</span><span class="nv">_</span><span class="p">)))</span> |
423 | | - <span class="p">((</span><span class="o">`#(</span><span class="nb">+</span> <span class="o">,</span><span class="nv">_</span><span class="p">)))</span> |
424 | | - <span class="p">((</span><span class="o">`#(</span><span class="nv">++</span> <span class="o">,</span><span class="nv">_</span><span class="p">)))</span> |
425 | | - <span class="p">((</span><span class="o">`#(</span><span class="nv">+++</span> <span class="o">,</span><span class="nv">_</span><span class="p">)))</span> |
426 | | - <span class="p">((</span><span class="o">`#(</span><span class="nb">-</span> <span class="o">,</span><span class="nv">_</span><span class="p">)))</span> |
427 | | - <span class="p">((</span><span class="o">`#(,</span><span class="nv">name</span> <span class="o">,</span><span class="nv">value</span><span class="p">))</span> |
428 | | - <span class="p">(</span><span class="nv">lfe_io:format</span> <span class="s">"~s: ~p~n"</span> <span class="o">`</span><span class="p">(</span><span class="o">,</span><span class="nv">name</span> <span class="o">,</span><span class="nv">value</span><span class="p">)))</span> |
429 | | - <span class="p">((</span><span class="nv">x</span><span class="p">)</span> <span class="p">(</span><span class="nv">filter-env</span> <span class="o">`#(</span><span class="nv">env</span> <span class="o">,</span><span class="nv">x</span><span class="p">))))</span> |
430 | | - <span class="nv">section</span><span class="p">))</span> |
431 | | - <span class="p">(</span><span class="nv">lists:nthtail</span> <span class="mi">1</span> <span class="p">(</span><span class="nv">tuple_to_list</span> <span class="nv">env</span><span class="p">))))</span> |
432 | | -<span class="nv">filter-env</span> |
433 | | -</code></pre></div> |
434 | | -<p>Now, as one hacks away in the REPL, <code>slurp</code>ing away at various modules, |
435 | | -getting a list of what's defined in the current environment is a piece of cake:</p> |
436 | | -<div class="highlight"><pre><code class="language-cl" data-lang="cl"><span class="nb">></span> <span class="p">(</span><span class="nv">filter-env</span> <span class="nv">$ENV</span><span class="p">)</span> |
437 | | -<span class="nv">my-var:</span> <span class="mi">42</span> |
438 | | -<span class="nv">my-func:</span> <span class="err">#</span><span class="nv">Fun<lfe_eval.23.86468545></span> |
439 | | -<span class="nv">script-args:</span> <span class="p">()</span> |
440 | | -<span class="nv">script-name:</span> <span class="s">"lfe"</span> |
441 | | -<span class="nv">MODULE:</span> <span class="o">#(</span><span class="nv">macro</span> <span class="p">(</span><span class="nv">match-lambda</span> <span class="p">(((</span><span class="nb">list</span><span class="p">)</span> <span class="nv">$ENV</span><span class="p">)</span> <span class="o">`</span><span class="ss">'joes-fav</span><span class="p">)))</span> |
442 | | -<span class="nv">c:</span> <span class="o">#(</span><span class="nv">macro</span> <span class="p">(</span><span class="k">lambda</span> <span class="p">(</span><span class="nv">args</span> <span class="nv">$ENV</span><span class="p">)</span> <span class="o">`</span><span class="p">(</span><span class="err">:</span> <span class="nv">lfe_shell</span> <span class="nv">c</span> <span class="o">,@</span><span class="nv">args</span><span class="p">)))</span> |
443 | | -<span class="nv">ec:</span> <span class="o">#(</span><span class="nv">macro</span> <span class="p">(</span><span class="k">lambda</span> <span class="p">(</span><span class="nv">args</span> <span class="nv">$ENV</span><span class="p">)</span> <span class="o">`</span><span class="p">(</span><span class="err">:</span> <span class="nv">lfe_shell</span> <span class="nv">ec</span> <span class="o">,@</span><span class="nv">args</span><span class="p">)))</span> |
444 | | -<span class="nv">exit:</span> <span class="o">#(</span><span class="k">function</span> <span class="p">(</span><span class="o">#(</span><span class="mi">0</span> <span class="o">#(</span><span class="nv">dynamic_expr</span> <span class="p">(</span><span class="k">lambda</span> <span class="p">()</span> <span class="p">(</span><span class="err">:</span> <span class="nv">lfe_shell</span> <span class="nv">exit</span><span class="p">))))))</span> |
445 | | -<span class="nv">factorial:</span> <span class="o">#(</span><span class="k">function</span> |
446 | | -<span class="o">...</span> |
447 | | -<span class="nv">ok</span> |
448 | | -<span class="nb">></span> |
449 | | -</code></pre></div> |
450 | | -<h3>1.5.4 Getting Out of Trouble</h3> |
451 | | - |
452 | | -<p>Every once in a while you may find that you do something which causes the REPL |
453 | | -to crash, presenting you with something that looks like this:</p> |
454 | | -<div class="highlight"><pre><code class="language-text" data-lang="text"> > |
455 | | - =ERROR REPORT==== 17-Feb-2013::15:39:33 === |
456 | | - ... |
457 | | -</code></pre></div> |
458 | | -<p>You don't have to quit and restart the REPL, if you don't want to! There are a |
459 | | -couple of steps that you can take instead.</p> |
460 | | - |
461 | | -<h4>1.5.4.1 Interrupting a Shell Process</h4> |
462 | | - |
463 | | -<p>When you get an error as seen above, type <code>^g</code>. This will put you into JCL |
464 | | -(Job Control Language) mode. At the JCL prompt, type <code>?</code> to see a list of |
465 | | -options:</p> |
466 | | -<div class="highlight"><pre><code class="language-text" data-lang="text"> User switch command |
467 | | - --> ? |
468 | | - c [nn] - connect to job |
469 | | - i [nn] - interrupt job |
470 | | - k [nn] - kill job |
471 | | - j - list all jobs |
472 | | - s [shell] - start local shell |
473 | | - r [node [shell]] - start remote shell |
474 | | - q - quit erlang |
475 | | - ? | h - this message |
476 | | -</code></pre></div> |
477 | | -<p>Let's see what's running:</p> |
478 | | -<div class="highlight"><pre><code class="language-text" data-lang="text"> --> j |
479 | | - 1* {lfe_shell,start,[]} |
480 | | -</code></pre></div> |
481 | | -<p>Our shell process is still alive, though not responding. Let's interrupt it and |
482 | | -then connect to it again:</p> |
483 | | -<div class="highlight"><pre><code class="language-text" data-lang="text"> --> i 1 |
484 | | - --> c 1 |
485 | | - exception error: function_clause |
486 | | - in (: lists sublist #(error interrupted) 1) |
487 | | - in (lfe_scan string 4) |
488 | | - in (lfe_io scan_and_parse 3) |
489 | | - |
490 | | - > |
491 | | -</code></pre></div> |
492 | | -<p>Once we interrupted the job, our error messages were printed to the REPL and we |
493 | | -were placed back at the LFE prompt.</p> |
494 | | - |
495 | | -<h4>1.5.4.2 Starting a New Shell</h4> |
496 | | - |
497 | | -<p>Sometimes, though, there is no shell process any more. Here's how to start up |
498 | | -a new shell process if the one that you're using dies:</p> |
499 | | -<div class="highlight"><pre><code class="language-text" data-lang="text"> --> s lfe_shell |
500 | | - --> j |
501 | | - 2* {lfe_shell,start,[]} |
502 | | - --> c 2 |
503 | | - LFE Shell V5.9.3.1 (abort with ^G) |
504 | | - > |
505 | | -</code></pre></div> |
506 | | -<p>And you're back up!</p> |
507 | | - |
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