Are you referring to 'dlgamma' function? Because there isn't any function named 'psi' in Scilab.

If you are referring to psi from last tutorials assignment question that was not any function it was simply a variable name in which you have to save Answer's value which is otherwise by default saved in ans variable name. 

<pre class="prettyprint" style="list-style: outside none none; margin-bottom: 0px; padding: 5px 0px 5px 5px; line-height: 1.4; background-color: rgb(255, 255, 255);"><span class="lit" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 102, 102);">@Test</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">public</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">void</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> markStatement</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">()</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">{</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> testHelper</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">getPsiClass</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> psiClasses </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">-></span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">{</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> assertThat</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">psiClasses</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">).</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">hasSize</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="lit" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 102, 102);">2</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">);</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">PsiClass</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> underTest </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">=</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> psiClasses</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">get</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="lit" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 102, 102);">0</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">);</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">PsiClass</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> component </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">=</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> psiClasses</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">get</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="lit" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 102, 102);">1</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">);</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="com" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(136, 0, 0);">// For testing environment</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">Function</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);"><</span><span class="highlight" style="list-style: outside none none; margin: 0px; padding: 1px 1px 1px 3px; background-color: rgb(227, 235, 202); border-radius: 2px;"><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">PsiMethodCallExpression</span></span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">,</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">PsiClass</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">></span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> resolver </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">=</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> ignored </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">-></span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> component</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">;</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">RequiredPropLineMarkerProvider</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> provider </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">=</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">new</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">RequiredPropLineMarkerProvider</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">resolver</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">);</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">List</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);"><</span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">PsiElement</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">></span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> statements </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">=</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">new</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">ArrayList</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);"><>(</span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">PsiTreeUtil</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">findChildrenOfAnyType</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">underTest</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">,</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="typ" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 0, 102);">PsiStatement</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">class</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">));</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> assertThat</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">provider</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">getLineMarkerInfo</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">statements</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">get</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="lit" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 102, 102);">0</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">))).</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">isNotNull</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">();</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> assertThat</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">provider</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">getLineMarkerInfo</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">statements</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">.</span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">get</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">(</span><span class="lit" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 102, 102);">1</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">))).</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);">isNull</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">();</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">return</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="kwd" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 136);">true</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">;</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">},</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="str" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 136, 0);">"RequiredPropAnnotatorTest.java"</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">,</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="str" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 136, 0);">"RequiredPropAnnotatorComponent.java"</span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">);</span><span class="pln" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(0, 0, 0);"> </span><span class="pun" style="list-style: outside none none; margin: 0px; padding: 0px; color: rgb(102, 102, 0);">}</span></pre>