introduce name~{expr} syntax in parser to dynamically create variable names (same as in getdp)

Parser/Gmsh.y

@@ -136,6 +136,7 @@ struct doubleXstring{
 %type <i> TransfiniteArrangement RecombineAngle
 %type <u> ColorExpr
 %type <c> StringExpr StringExprVar SendToFile HomologyCommand
+%type <c> StringIndex String__Index
 %type <l> RecursiveListOfStringExprVar
 %type <l> FExpr_Multi ListOfDouble ListOfDoubleOrAll RecursiveListOfDouble
 %type <l> RecursiveListOfListOfDouble Enumeration
@@ -617,7 +618,7 @@ Affectation :
 
   | tUndefineConstant '[' UndefineConstants ']' tEND
 
-  | tSTRING NumericAffectation ListOfDouble tEND
+  | String__Index NumericAffectation ListOfDouble tEND
     {
       if(!gmsh_yysymbols.count($1) && $2 && List_Nbr($3) == 1){
         yymsg(0, "Unknown variable '%s'", $1);
@@ -873,7 +874,7 @@ Affectation :
       List_Delete($8);
     }
 
-  | tSTRING NumericIncrement tEND
+  | String__Index NumericIncrement tEND
     {
       if(!gmsh_yysymbols.count($1))
 	yymsg(0, "Unknown variable '%s'", $1);
@@ -904,7 +905,7 @@ Affectation :
       }
       Free($1);
     }
-  | tSTRING tAFFECT StringExpr tEND
+  | String__Index tAFFECT StringExpr tEND
     {
       gmsh_yystringsymbols[$1] = std::string($3);
       Free($1);
@@ -1182,7 +1183,7 @@ Comma : /* none */ | ',' ;
 
 DefineConstants :
     /* none */
-  | DefineConstants Comma tSTRING
+  | DefineConstants Comma String__Index
     {
       std::string key($3);
       std::vector<double> val(1, 0.);
@@ -1193,7 +1194,7 @@ DefineConstants :
       }
       Free($3);
     }
-  | DefineConstants Comma tSTRING tAFFECT FExpr
+  | DefineConstants Comma String__Index tAFFECT FExpr
     {
       std::string key($3);
       std::vector<double> val(1, $5);
@@ -1204,7 +1205,7 @@ DefineConstants :
       }
       Free($3);
     }
-  | DefineConstants Comma tSTRING tAFFECT '{' FExpr
+  | DefineConstants Comma String__Index tAFFECT '{' FExpr
     { floatOptions.clear(); charOptions.clear(); }
     FloatParameterOptions '}'
     {
@@ -1216,7 +1217,7 @@ DefineConstants :
       }
       Free($3);
     }
-  | DefineConstants Comma tSTRING tAFFECT StringExpr
+  | DefineConstants Comma String__Index tAFFECT StringExpr
     {
       std::string key($3), val($5);
       floatOptions.clear(); charOptions.clear();
@@ -1227,7 +1228,7 @@ DefineConstants :
       Free($3);
       Free($5);
     }
-  | DefineConstants Comma tSTRING tAFFECT '{' StringExpr
+  | DefineConstants Comma String__Index tAFFECT '{' StringExpr
     { floatOptions.clear(); charOptions.clear(); }
       CharParameterOptions '}'
     {
@@ -4346,7 +4347,7 @@ FExpr_Single :
 
   // Variables
 
-  | tSTRING
+  | String__Index
     {
       if(!gmsh_yysymbols.count($1)){
 	yymsg(0, "Unknown variable '%s'", $1);
@@ -4364,28 +4365,6 @@ FExpr_Single :
       Free($1);
     }
 
-  // for compatibility with GetDP (we should generalize it so
-  // that we can create variables with this syntax, use them
-  // recursively, etc., but I don't have time to do it now)
-  | tSTRING '~' '{' FExpr '}'
-    {
-      char tmpstring[1024];
-      sprintf(tmpstring, "%s_%d", $1, (int)$4) ;
-      if(!gmsh_yysymbols.count(tmpstring)){
-	yymsg(0, "Unknown variable '%s'", tmpstring);
-	$$ = 0.;
-      }
-      else{
-        gmsh_yysymbol &s(gmsh_yysymbols[tmpstring]);
-        if(s.value.empty()){
-          yymsg(0, "Uninitialized variable '%s'", tmpstring);
-          $$ = 0.;
-        }
-        else
-          $$ = s.value[0];
-      }
-      Free($1);
-    }
   | tSTRING '[' FExpr ']'
     {
       int index = (int)$3;
@@ -4416,7 +4395,7 @@ FExpr_Single :
       }
       Free($2);
     }
-  | tSTRING NumericIncrement
+  | String__Index NumericIncrement
     {
       if(!gmsh_yysymbols.count($1)){
 	yymsg(0, "Unknown variable '%s'", $1);
@@ -5012,7 +4991,7 @@ StringExprVar :
     {
       $$ = $1;
     }
-  | tSTRING
+  | String__Index
     {
       if(!gmsh_yystringsymbols.count($1)){
 	yymsg(0, "Unknown string variable '%s'", $1);
@@ -5213,6 +5192,38 @@ RecursiveListOfStringExprVar :
     { List_Add($$, &($3)); }
  ;
 
+StringIndex :
+
+    tSTRING '~' '{' FExpr '}'
+    {
+      char tmpstr[256];
+      sprintf(tmpstr, "_%d", (int)$4);
+      $$ = (char *)Malloc((strlen($1)+strlen(tmpstr)+1)*sizeof(char));
+      strcpy($$, $1); strcat($$, tmpstr);
+      Free($1);
+    }
+
+  | StringIndex '~' '{' FExpr '}'
+    {
+      char tmpstr[256];
+      sprintf(tmpstr, "_%d", (int)$4);
+      $$ = (char *)Malloc((strlen($1)+strlen(tmpstr)+1)*sizeof(char)) ;
+      strcpy($$, $1) ; strcat($$, tmpstr) ;
+      Free($1);
+    }
+
+ ;
+
+String__Index :
+
+    tSTRING
+    { $$ = $1; }
+
+  | StringIndex
+    { $$ = $1; }
+
+ ;
+
 %%
 
 int PrintListOfDouble(char *format, List_T *list, char *buffer)

doc/texinfo/gmsh.texi

@@ -969,6 +969,7 @@ parsing of the script file:
 @var{expression}:
   @var{real} |
   @var{string} |
+  @var{string} ~ @{ @var{expression} @}
   @var{string} [ @var{expression} ] |
   # @var{string} [ ] |
   ( @var{expression} ) |
@@ -985,19 +986,37 @@ parsing of the script file:
 @end example
 
 Such @w{@var{expression}s} are used in most of Gmsh's scripting
-commands.  The third and fourth cases in this definition permit to
-extract one item from a list (see below) and get the size of a list,
-respectively. The operators @var{operator-unary-left},
-@var{operator-unary-right}, @var{operator-binary},
-@var{operator-ternary-left} and @var{operator-ternary-right} are defined
-in @ref{Operators}. For the definition of @w{@var{built-in-function}s},
-see @ref{Built-in functions}. The various @w{@var{real-option}s} are
-listed in @ref{Options}. @code{StrFind} searches the first
-@var{char-expression} for any occurrence of the second
-@var{char-expression}. @code{StrCmp} compares the two strings (returns
-an integer greater than, equal to, or less than 0, according as the
-first string is greater than, equal to, or less than the second string).
-@code{TextAttributes} creates attributes for text strings.
+commands. When @code{~@{@var{expression-cst}@}} is appended to a string
+@var{string}, the result is a new string formed by the concatenation of
+@var{string}, @code{_} (an underscore) and the value of the
+@var{expression-cst}. This is most useful in loops (@pxref{Loops and
+conditionals}), where it permits to define unique strings
+automatically. For example,
+@example
+For i In @{1:3@}
+  x~@{i@} = i;
+EndFor
+@end example
+is the same as
+@example
+x_1 = 1;
+x_2 = 2;
+x_3 = 3;
+@end example
+
+The brackets @code{[]} permit to extract one item from a list and to get
+the size of a list, respectively. The operators
+@var{operator-unary-left}, @var{operator-unary-right},
+@var{operator-binary}, @var{operator-ternary-left} and
+@var{operator-ternary-right} are defined in @ref{Operators}. For the
+definition of @w{@var{built-in-function}s}, see @ref{Built-in
+functions}. The various @w{@var{real-option}s} are listed in
+@ref{Options}. @code{StrFind} searches the first @var{char-expression}
+for any occurrence of the second @var{char-expression}. @code{StrCmp}
+compares the two strings (returns an integer greater than, equal to, or
+less than 0, according as the first string is greater than, equal to, or
+less than the second string).  @code{TextAttributes} creates attributes
+for text strings.
 
 The last case in the definition allows to ask the user for a value
 interactively. For example, inserting @code{GetValue("Value of parameter