parse_8cpp-source.html

parser in C++~~~~~~~~~~~~

00197   }
00198   <span class="keywordflow">return</span> <span class="keyword">true</span>;
00199 }
00200 
<a name="l00205"></a><a class="code" href="parse_8cpp.html#a7">00205</a> <a class="code" href="classCell.html">Cell</a>* <a class="code" href="parse_8cpp.html#a7">makecell</a>(string str)
00206 {
00207   <a class="code" href="classCell.html">Cell</a>* root;
00208   <span class="keywordflow">if</span> (((str[0] &gt;= <span class="charliteral">'0'</span>) &amp;&amp; (str[0] &lt;= <span class="charliteral">'9'</span>)) || (str[0] == <span class="charliteral">'.'</span>) 
00209       || (((<span class="charliteral">'+'</span>==str[0]) || (<span class="charliteral">'-'</span>==str[0]))&amp;&amp;(str.length()&gt;1))) {
00210     <span class="keywordflow">if</span> (<span class="keyword">false</span> == <a class="code" href="parse_8cpp.html#a2">is_legalnumeric</a>(str)) {
00211       cout &lt;&lt; <span class="stringliteral">"error: illegal numeric literal"</span> &lt;&lt; endl;
00212       exit(1);
00213     }
00214     <span class="comment">// this is a numeric literal</span>
00215     <span class="keywordflow">if</span> (string::npos == str.find(<span class="charliteral">'.'</span>)) {
00216       <span class="comment">// int number</span>
00217       <span class="keywordtype">char</span>* fchar = const_cast&lt;char*&gt;(str.c_str());
00218       <span class="keywordtype">int</span> value = atoi(fchar);
00219       root = <a class="code" href="cons_8hpp.html#a1">make_int</a>(value);
00220     } <span class="keywordflow">else</span> {
00221       <span class="comment">// this is a double</span>
00222       <span class="keywordtype">char</span>* fchar = const_cast&lt;char*&gt;(str.c_str());
00223       <span class="keywordtype">double</span> value = atof(fchar);   
00224       root = <a class="code" href="cons_8hpp.html#a2">make_double</a>(value);
00225     }
00226   } 
00227   
00228   <span class="comment">// we don't deal with literal strings right now, so they are commented out</span>
00229   <span class="comment">// else if (str[0] == '\"') {</span>
00230 <span class="comment">//     // this is a string literal</span>
00231 <span class="comment">//     string strval = str.substr(1, str.size() - 2);</span>
00232 <span class="comment">//     root = make_string(const_cast&lt;char*&gt;(strval.data()));</span>
00233 <span class="comment">//   } </span>
00234   <span class="keywordflow">else</span> {
00235     <span class="comment">// this is a symbol</span>
00236     <span class="keywordflow">if</span> (<span class="keyword">false</span> == <a class="code" href="parse_8cpp.html#a3">is_legaloperator</a>(str)) {
00237       cout &lt;&lt; <span class="stringliteral">"error: illegal operator"</span> &lt;&lt; endl;
00238       exit(1);
00239     }
00240     root = <a class="code" href="cons_8hpp.html#a3">make_symbol</a>(const_cast&lt;char*&gt;(str.data()));
00241   }
00242   <span class="keywordflow">return</span> root;
00243 }
00244 
00245 <a class="code" href="classCell.html">Cell</a>* <a class="code" href="parse_8cpp.html#a8">separate_parse</a>(string&amp; sexpr); 
00246 
<a name="l00247"></a><a class="code" href="parse_8hpp.html#a0">00247</a> <a class="code" href="classCell.html">Cell</a>* <a class="code" href="parse_8hpp.html#a0">parse</a>(string sexpr)
00248 {
00249   <span class="comment">// is_legal(sexpr);</span>
00250   <span class="comment">// delete the whitesapce at the begining and end</span>
00251   <span class="comment">// such that the first and last character are not white space</span>
00252   <a class="code" href="parse_8cpp.html#a5">clearwhitespace</a>(sexpr);
00253 <span class="comment">//   if (sexpr.length() == 0) {</span>
00254 <span class="comment">//     return NULL;</span>
00255 <span class="comment">//   }</span>
00256   <span class="keywordflow">if</span> (sexpr.length() == 0) {
00257     <span class="keywordflow">return</span> NULL;
00258   }
00259   <span class="keywordflow">if</span> ( !<a class="code" href="parse_8cpp.html#a6">is_legalexpr</a>(sexpr)) {
00260     <span class="keywordflow">return</span> NULL;
00261   }
00262   <span class="comment">// check whether is single symbol</span>
00263   <span class="comment">// i.e. leaf cell</span>
00264   <span class="comment">// if (string::npos == sexpr.find('(')) {</span>
00265   <span class="keywordflow">if</span> (<span class="charliteral">'('</span> != sexpr[0]) {
00266     <span class="comment">// this is leaf cell</span>
00267     <span class="comment">// bulid this leaf cell</span>
00268     <a class="code" href="classCell.html">Cell</a>* root = <a class="code" href="parse_8cpp.html#a7">makecell</a>( sexpr );
00269     <span class="keywordflow">return</span> root;
00270   }
00271 
00272   <span class="comment">// the first and last character are '(' and ')', respectively</span>
00273   <span class="comment">// delete the two characters</span>
00274   <span class="keywordtype">int</span> length = sexpr.size();
00275   sexpr = sexpr.substr(1, length-2);
00276   <a class="code" href="parse_8cpp.html#a5">clearwhitespace</a>(sexpr);
00277   length = sexpr.size();
00278 <span class="comment">//   if ( inparsecar ) {</span>
00279 <span class="comment">//     if (sexpr == "") {</span>
00280 <span class="comment">//       Cell* ec = new Cell("()");</span>
00281 <span class="comment">//       return ec;</span>
00282 <span class="comment">//     }</span>
00283 <span class="comment">//   }</span>
00284   <span class="comment">// separate the s-expression into two left and right subsexps</span>
00285   <a class="code" href="classCell.html">Cell</a>* root = <a class="code" href="parse_8cpp.html#a8">separate_parse</a>(sexpr);
00286 
00287   <span class="keywordflow">return</span> root;
00288 }
00289 
<a name="l00295"></a><a class="code" href="parse_8cpp.html#a8">00295</a> <a class="code" href="classCell.html">Cell</a>* <a class="code" href="parse_8cpp.html#a8">separate_parse</a>(string&amp; instr)
00296 {
00297   string sexp;
00298   <span class="keywordtype">bool</span> isstartsexp = <span class="keyword">false</span>;
00299   <span class="keywordtype">int</span> inumleftparenthesis = 0;
00300 
00301   <span class="comment">// check whether to read the end</span>
00302   <a class="code" href="parse_8cpp.html#a5">clearwhitespace</a>(instr);
00303   <span class="keywordtype">int</span> length = instr.size();
00304     <span class="comment">// check whether it is a "()" sexpr</span>
00305 
00306   <span class="keywordflow">while</span> (instr.size() &gt; 0) {
00307     <span class="comment">// read char by char</span>
00308     <span class="keywordtype">char</span> currentchar = instr[0];
00309     <span class="comment">// skip some white space before new s-expression occurs</span>
00310     <span class="keywordflow">if</span> ((<span class="keyword">true</span> == <a class="code" href="parse_8hpp.html#a1">iswhitespace</a>(currentchar))&amp;&amp;(<span class="keyword">false</span> == isstartsexp)) {
00311       <span class="keywordflow">continue</span>;
00312     }
00313     <span class="comment">// run accross a new s-expression</span>
00314     <span class="keywordflow">if</span> ((<span class="keyword">false</span> == isstartsexp)&amp;&amp;(<span class="keyword">false</span> == <a class="code" href="parse_8hpp.html#a1">iswhitespace</a>(currentchar))) {
00315       <span class="comment">// check whether single symbol</span>
00316       <span class="keywordflow">if</span> (<span class="charliteral">'('</span> != currentchar) {
00317         <span class="comment">// read single a single symbol</span>
00318         <a class="code" href="main_8cpp.html#a1">readsinglesymbol</a>(instr, sexp);
00319         <a class="code" href="parse_8cpp.html#a5">clearwhitespace</a>(instr);  
00320         inparsecar = <span class="keyword">true</span>;
00321         <a class="code" href="classCell.html">Cell</a>* <a class="code" href="cons_8hpp.html#a13">car</a> = <a class="code" href="parse_8hpp.html#a0">parse</a>(sexp);
00322         inparsecar = <span class="keyword">false</span>;
00323         <a class="code" href="classCell.html">Cell</a>* <a class="code" href="cons_8hpp.html#a14">cdr</a> = <a class="code" href="parse_8hpp.html#a0">parse</a>(<span class="stringliteral">"("</span> + instr + <span class="stringliteral">")"</span>);
00324         <a class="code" href="classCell.html">Cell</a>* root = <a class="code" href="cons_8hpp.html#a4">cons</a>(<a class="code" href="cons_8hpp.html#a13">car</a>, <a class="code" href="cons_8hpp.html#a14">cdr</a>);
00325         sexp.clear();
00326         <span class="keywordflow">return</span> root;
00327       } <span class="keywordflow">else</span> {
00328         <span class="comment">// start new expression</span>
00329         isstartsexp = <span class="keyword">true</span>;
00330         <span class="comment">// read left parenthesiss</span>
00331         sexp += currentchar;
00332         instr = instr.substr(1, instr.size() -1);
00333         inumleftparenthesis = 1;
00334       }
00335     } <span class="keywordflow">else</span> {
00336       <span class="comment">// in the process of reading the current s-expression</span>
00337       <span class="keywordflow">if</span> (<span class="keyword">true</span> == isstartsexp) {
00338         <span class="keywordflow">if</span> (<span class="keyword">true</span> == <a class="code" href="parse_8hpp.html#a1">iswhitespace</a>(currentchar)) {
00339           <span class="comment">// append a blankspace</span>
00340           sexp += <span class="charliteral">' '</span>;
00341           instr = instr.substr(1, instr.size() -1);
00342         } <span class="keywordflow">else</span> {
00343           <span class="comment">// append current character</span>
00344           sexp += currentchar;
00345           instr = instr.substr(1, instr.size() -1);
00346           <span class="comment">// count left parenthesiss</span>
00347           <span class="keywordflow">if</span> (<span class="charliteral">'('</span> == currentchar) {
00348             inumleftparenthesis ++;
00349           }
00350           <span class="keywordflow">if</span> (<span class="charliteral">')'</span> == currentchar) {
00351             inumleftparenthesis --;
00352 
00353             <span class="comment">// check whether current s-expression ends</span>
00354             <span class="keywordflow">if</span> (0 == inumleftparenthesis) {
00355               <span class="comment">// current s-expression ends</span>
00356               isstartsexp = <span class="keyword">false</span>;
00357               <a class="code" href="parse_8cpp.html#a5">clearwhitespace</a>(instr);
00358               inparsecar = <span class="keyword">true</span>;
00359               <a class="code" href="classCell.html">Cell</a>* <a class="code" href="cons_8hpp.html#a13">car</a> = <a class="code" href="parse_8hpp.html#a0">parse</a>(sexp);        
00360               inparsecar = <span class="keyword">false</span>;
00361               <span class="keywordtype">int</span> length = instr.length();
00362               <a class="code" href="classCell.html">Cell</a>* cdr;
00363               <a class="code" href="classCell.html">Cell</a>* root;
00364               <span class="keywordflow">if</span> (length &lt;= 0) {
00365                 <a class="code" href="cons_8hpp.html#a14">cdr</a> = NULL;
00366               } <span class="keywordflow">else</span> {
00367                 <a class="code" href="cons_8hpp.html#a14">cdr</a> = <a class="code" href="parse_8hpp.html#a0">parse</a>(<span class="stringliteral">"("</span> + instr + <span class="stringliteral">")"</span>);       
00368               }
00369               root = <a class="code" href="cons_8hpp.html#a4">cons</a>(<a class="code" href="cons_8hpp.html#a13">car</a>, <a class="code" href="cons_8hpp.html#a14">cdr</a>);
00370               sexp.clear();
00371               <span class="keywordflow">return</span> root;     
00372             }
00373           }
00374         }
00375       }
00376     }
00377   }
00378 
00379   <span class="keywordflow">return</span> NULL;
00380 }
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