Initial revision

util/cpp/expression.g

@@ -0,0 +1,124 @@
+/*	EXPRESSION SYNTAX PARSER	*/
+
+%lexical	LLlex;
+%start		If_expr, if_expression;
+
+{
+#include	"LLlex.h"
+
+extern int ifval;
+}
+
+if_expression
+:
+	constant_expression(&ifval)
+;
+
+/* 7.1 */
+primary(int *pval;)
+:
+	constant(pval)
+|
+	'(' expression(pval) ')'
+;
+
+unary(int *pval;)
+	{int oper;}
+:
+	unop(&oper)
+	unary(pval)
+	{ ch7mon(oper, pval); }
+|
+	primary(pval)
+;
+
+binary_expression(int maxrank; int *pval;)
+	{int oper; int val1;}
+:
+	unary(pval)
+	[%while (rank_of(DOT) <= maxrank)
+		binop(&oper)
+		binary_expression(rank_of(oper)-1, &val1)
+		{
+			ch7bin(pval, oper, val1);
+		}
+	]*
+;
+
+/* 7.13 */
+conditional_expression(int *pval;)
+	{int val1 = 0, val2 = 0;}
+:
+	/* allow all binary operators */
+	binary_expression(rank_of('?') - 1, pval)
+	[	'?'
+		expression(&val1)
+		':'
+		assignment_expression(&val2)
+		{ *pval = (*pval ? val1 : val2); }
+	]?
+;
+
+/* 7.14 */
+assignment_expression(int *pval;)
+:
+	conditional_expression(pval)
+;
+
+/* 7.15 */
+expression(int *pval;)
+	{int val1;}
+:
+	assignment_expression(pval)
+	[	','
+		assignment_expression(&val1)
+		{
+			ch7bin(pval, ',', val1);
+		}
+	]*
+;
+
+unop(int *oper;) :
+	[ '-' | '!' | '~' ]
+	{*oper = DOT;}
+;
+
+multop:
+	'*' | '/' | '%'
+;
+
+addop:
+	'+' | '-'
+;
+
+shiftop:
+	LEFT | RIGHT
+;
+
+relop:
+	'<' | '>' | LESSEQ | GREATEREQ
+;
+
+eqop:
+	EQUAL | NOTEQUAL
+;
+
+arithop:
+	multop | addop | shiftop
+|
+	'&' | '^' | '|'
+;
+
+binop(int *oper;) :
+	[ arithop | relop | eqop | AND | OR ]
+	{*oper = DOT;}
+;
+
+constant(int *pval;) :
+	INTEGER
+	{*pval = dot.tk_val;}
+;
+
+constant_expression (int *pval;) :
+	assignment_expression(pval)
+;