From 9b8f4377239986cdd1f9490c078239f321a566f7 Mon Sep 17 00:00:00 2001
From: Nick Downing <downing.nick@gmail.com>
Date: Thu, 21 Jun 2018 23:14:19 +1000
Subject: [PATCH] Add another version slightly cleaned up and using flex/bison
 with a header file

---
 .gitignore |  4 ++++
 Makefile   | 18 +++++++++++++++++-
 calc.l     | 14 ++++++++++++++
 calc.y     | 41 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 calc.l
 create mode 100644 calc.y

diff --git a/.gitignore b/.gitignore
index d719633..c41a4fd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,7 @@
 cal
 lex.yy.c
 y.tab.c
+calc
+calc.tab.c
+calc.tab.h
+calc.yy.c
diff --git a/Makefile b/Makefile
index ecd7219..b1c5ad5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,6 @@
+all: cal calc
+
+# cal program
 cal: y.tab.o
 	${CC} -o $@ $<
 
@@ -9,5 +12,18 @@ y.tab.c: cal.y
 lex.yy.c: cal.l
 	lex $<
 
+# calc program
+calc: calc.tab.o calc.yy.o
+	gcc -o $@ calc.tab.o calc.yy.o
+
+calc.tab.h: calc.tab.c
+calc.tab.c: calc.y
+	bison -d $<
+
+calc.yy.o: calc.yy.c calc.tab.h
+calc.yy.c: calc.l
+	flex -o $@ $<
+
+# other
 clean:
-	rm -f *.o cal lex.yy.c y.tab.c
+	rm -f *.o cal lex.yy.c y.tab.c calc calc.tab.c calc.tab.h calc.yy.c
diff --git a/calc.l b/calc.l
new file mode 100644
index 0000000..4bb295a
--- /dev/null
+++ b/calc.l
@@ -0,0 +1,14 @@
+%{
+#define YYSTYPE double
+#include "calc.tab.h"
+%}
+
+DIGIT [0-9]+\.?|[0-9]*\.[0-9]+
+
+%option noyywrap
+
+%%
+
+[ ]
+{DIGIT}	{ yylval = atof(yytext); return NUM; }
+\n|.	{ return yytext[0]; }
diff --git a/calc.y b/calc.y
new file mode 100644
index 0000000..d0efd30
--- /dev/null
+++ b/calc.y
@@ -0,0 +1,41 @@
+%{
+#include <stdio.h>
+#include <stdlib.h>
+#define YYSTYPE double
+%}
+
+%token NUM
+
+%left '+' '-'
+%left '*' '/'
+%right UMINUS
+
+%%
+
+S : S E '\n' { printf("Answer: %g\nEnter:\n", $2); }
+  | S '\n'
+  |
+  | error '\n' { yyerror("Error: Enter once more...\n"); yyerrok; }
+  ;
+E : E '+' E { $$ = $1 + $3; }
+  | E '-' E { $$ = $1 - $3; }
+  | E '*' E { $$ = $1 * $3; }
+  | E '/' E { $$ = $1 / $3; }
+  | '(' E ')' { $$ = $2; }
+  | '-' E %prec UMINUS { $$ = -$2; }
+  | NUM
+  ;
+
+%%
+
+int main()
+{
+  printf("Enter the expression:\n");
+  yyparse();
+}
+
+yyerror(char * s)
+{
+  printf("%s\n", s);
+  exit(EXIT_FAILURE);
+}
-- 
2.34.1