https://forge.codesys.com/forge/talk/CODESYS-V2/thread/744dfd31c5/2020-02-27T22:21:34.644000ZRecent posts to work with pointer2020-02-27T22:21:34.644000Z2020-02-27T22:21:34.644000ZRobiHerbhttps://forge.codesys.com/u/robiherb/https://forge.codesys.come5a994b1d6e32d79a854988f2fb0c4f1bea8b15d

<div class="markdown_content"><p>Ist there any information about pointer arithmetic in st?</p> <p>Try and error is a bad solution for me. </p></div>

2020-02-27T22:21:30.260000Z2020-02-27T22:21:30.260000ZRalph Holzhttps://forge.codesys.com/u/ralph-holz/https://forge.codesys.com80d45db1639812d7317c27647aab96ef9cbed2f1

<div class="markdown_content"><p>Hi Paul!</p> <blockquote> <p><strong>Zitat:</strong><br/> value := actual_var^<span>[5]</span>.x; (<em> didn't work </em>) </p> </blockquote> <p>Your Pointer is no array of something so you cant use indexes</p> <blockquote> <p><strong>Zitat:</strong><br/> actual_var := actual_var + ( sizeof(target) * 5); (<em> didn't work </em>) </p> </blockquote> <p>Only sizeof(Variable) not Sizeof(Datatype) is possible.</p> <p>See the solutions below:</p> <div class="codehilite"><pre><span></span><span class="nt">VAR</span> <span class="err"> </span> <span class="err"> </span><span class="nt">var1</span> <span class="o">:</span> <span class="nt">ARRAY</span> <span class="cp">[</span><span class="mi">1</span><span class="nx">..30</span><span class="cp">]</span> <span class="nt">OF</span> <span class="nt">target</span><span class="o">;</span> <span class="err"> </span> <span class="err"> </span><span class="nt">actual_var</span> <span class="o">:</span> <span class="nt">POINTER</span> <span class="nt">TO</span> <span class="nt">ARRAY</span> <span class="cp">[</span><span class="mi">1</span><span class="nx">..30</span><span class="cp">]</span> <span class="nt">OF</span> <span class="nt">target</span><span class="o">;</span> <span class="err"> </span> <span class="err"> </span><span class="nt">actual_var2</span><span class="o">:</span> <span class="nt">POINTER</span> <span class="nt">TO</span> <span class="nt">target</span><span class="o">;</span> <span class="err"> </span> <span class="err"> </span><span class="nt">value</span><span class="o">:</span> <span class="nt">BYTE</span><span class="o">;</span> <span class="err"> </span> <span class="err"> </span><span class="nt">value2</span><span class="o">:</span> <span class="nt">BYTE</span><span class="o">;</span> <span class="nt">END_VAR</span> <span class="nt">actual_var</span><span class="o">:=</span> <span class="nt">ADR</span><span class="o">(</span><span class="nt">var1</span><span class="o">);</span> <span class="nt">value</span> <span class="o">:=</span> <span class="nt">actual_var</span><span class="o">^</span><span class="cp">[</span><span class="mi">5</span><span class="cp">]</span><span class="p">.</span><span class="nc">x</span><span class="o">;</span> <span class="o">(*</span> <span class="nt">works</span> <span class="o">*)</span> <span class="nt">actual_var2</span><span class="o">:=</span> <span class="nt">ADR</span><span class="o">(</span><span class="nt">var1</span><span class="o">);</span> <span class="nt">actual_var2</span> <span class="o">:=</span> <span class="nt">actual_var2</span> <span class="o">+</span> <span class="nt">SIZEOF</span><span class="o">(</span><span class="nt">actual_var2</span><span class="o">^)</span> <span class="o">*</span> <span class="nt">DWORD</span><span class="p">#</span><span class="nn">4</span><span class="o">;</span> <span class="o">(*</span> <span class="nt">works</span> <span class="o">*)</span> <span class="nt">value2</span><span class="o">:=</span> <span class="nt">actual_var2</span><span class="o">^</span><span class="p">.</span><span class="nc">x</span><span class="o">;</span> </pre></div> </div>

2020-02-27T22:21:28.696000Z2020-02-27T22:21:28.696000ZPaulhttps://forge.codesys.com/u/paul/https://forge.codesys.com3f3a118e5fea593c6c5e81662aff960134ee29ec

<div class="markdown_content"><p>I have array on structure target (x: byte, y : byte). </p> <p>var1 : array <span>[1..30]</span> of target;</p> <p>actual_var : pointer to target;</p> <hr/> <p>value := actual_var^<span>[5]</span>.x; (<em> didn't work </em>)</p> <p>actual_var := actual_var + ( sizeof(target) * 5); (<em> didn't work </em>)</p> <p>Where is problem?</p> <p>Thanks Paul</p></div>