From: Alexei Sheplyakov <varg@theor.jinr.ru>
Date: Sat, 13 Sep 2008 00:30:22 +0000 (+0400)
Subject: parser: map input strings onto arbitrary expressions (not only symbols).
X-Git-Tag: release_1-5-0~59^2~12
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=58a84c0adac7cbaa63a50c06815aed9c7a0bcdcc;hp=949508429ea9850b8ec36d862f4e4d291773c313

parser: map input strings onto arbitrary expressions (not only symbols).

So it's possible to make abbreviations, e.g.

symbol x;
symtab table;
table["x"] = x + log(x) + 1;
parser reader(table);
ex e = reader("1 + x^2 + 5*x^3");
---

diff --git a/ginac/parser/parse_context.cpp b/ginac/parser/parse_context.cpp
index e4956ba7..1dd76777 100644
--- a/ginac/parser/parse_context.cpp
+++ b/ginac/parser/parse_context.cpp
@@ -4,23 +4,28 @@
 namespace GiNaC
 {
 
-const symbol&
+symbol
 find_or_insert_symbol(const std::string& name, symtab& syms, const bool strict)
 {
 	symtab::const_iterator p = syms.find(name);
-	if (p != syms.end())
-		return p->second.first;
+	if (p != syms.end()) {
+		if (is_a<symbol>(p->second))
+			return ex_to<symbol>(p->second);
+		else
+			throw std::invalid_argument(
+				std::string("find_or_insert_symbol: name \"")
+				+ name + "\" does not correspond to a symbol");
+	}
+
 
 	if (strict)
 		throw std::invalid_argument(
 				std::string("find_or_insert_symbol: symbol \"") 
 				+ name + "\" not found");
 
-	// false means this symbol was created by parser 
-	const std::pair<symbol, bool> tmp = std::make_pair(symbol(name), false);
-
-	symtab::iterator i = syms.insert(symtab::value_type(name, tmp)).first;
-	return i->second.first;
+	const symbol sy(name);
+	syms[name] = sy;
+	return sy;
 }
 
 }
diff --git a/ginac/parser/parse_context.hpp b/ginac/parser/parse_context.hpp
index d0a3d558..efcb6c62 100644
--- a/ginac/parser/parse_context.hpp
+++ b/ginac/parser/parse_context.hpp
@@ -11,14 +11,11 @@ namespace GiNaC
 {
 
 /**
- * Establishes correspondence between the strings and symbols.
+ * Establishes correspondence between the strings and expressions.
  * The parser will create missing symbols (if not instructed otherwise,
  * in which case it fails if the expression contains unknown symbols).
- * The .second element of pair helps to distinguish between the user
- * supplied symbols and parser generated ones. The .first is the symbol
- * itself
  */
-typedef std::map<std::string, std::pair<symbol, bool> > symtab;
+typedef std::map<std::string, ex> symtab;
 
 /**
  * Find the symbol with the @a name in the symbol table @a syms.
@@ -26,7 +23,7 @@ typedef std::map<std::string, std::pair<symbol, bool> > symtab;
  * If symbol is missing and @a strict = false, insert it, otherwise
  * throw an exception.
  */
-extern const symbol&
+extern symbol
 find_or_insert_symbol(const std::string& name, symtab& syms,
 	              const bool strict);