basic calculator

.gitignore

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+# ignore generated parser
+calc.c
+
+# ignore compiled parser
+calc

Makefile

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+CC=cc
+PG=leg
+
+cparser: calc.c
+	$(CC) -o calc calc.c
+
+calc.c: calc.leg
+	$(PG) calc.leg > calc.c
+
+clean:
+	rm calc.c calc

calc.leg

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+%{
+
+/* compile: leg -o tmp.c tmp.leg
+ *			cc -o tmp tmp.c
+ *
+ * run:		echo "hello world" | ./tmp
+ */
+
+#define YYSTYPE int
+YYSTYPE yylval = 0;
+
+%}
+
+start	=	e:exp					{ yylval = e }
+
+exp		=	- s:sum					{ $$ = s }
+
+sum		=	PLUS* l:prod
+			( PLUS+ r:prod			{ l += r }
+			| MINUS r:prod			{ l -= r }
+			)*						{ $$ = l }
+
+prod	=	l:neg
+			( MULTI		r:neg		{ l *= r }
+			| DIVIDE	r:neg		{ l /= r }
+            | MODULO    r:neg       { l %= r }
+			)*						{ $$ = l }
+
+neg		=	MINUS n:neg				{ $$ = -n }
+			| n:NUMBER				{ $$ = n }
+
+-		=	[ \t]*
+NUMBER	=	< [0-9]+ >	-			{ $$ = atoi(yytext) }
+PLUS	=	'+'			-
+MINUS	=	'-'			-
+MULTI	=	'*'			-
+DIVIDE	=	'/'			-
+MODULO  =   '%'         -
+%%
+
+int main(int argc, char **argv)
+{
+	while (yyparse()) {
+		printf("%d\n", yylval);
+	}
+
+	return 0;
+}

test.sh

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+#!/bin/bash
+PROG=calc
+
+make
+
+echo "2+3" | ./${PROG} | cmp <(echo "5") && echo "test#1 passed!" || true
+echo "2-3" | ./${PROG} | cmp <(echo "-1") && echo "test#2 passed!" || true
+echo "2--3" | ./${PROG} | cmp <(echo "5") && echo "test#3 passed!" || true
+echo "-2+3" | ./${PROG} | cmp <(echo "1") && echo "test#4 passed!" || true
+echo "+2+3" | ./${PROG} | cmp <(echo "5") && echo "test#5 passed!" || true
+echo "2*3" | ./${PROG} | cmp <(echo "6") && echo "test#6 passed!" || true
+echo "4/2" | ./${PROG} | cmp <(echo "2") && echo "test#6 passed!" || true
+echo "3/2" | ./${PROG} | cmp <(echo "1") && echo "test#7 passed!" || true
+echo "5%2" | ./${PROG} | cmp <(echo "1") && echo "test#8 passed!" || true
+echo "3*2+10*2" | ./${PROG} | cmp <(echo "26") && echo "test#9 passed!" || true
+echo "-3*2+10*2" | ./${PROG} | cmp <(echo "14") && echo "test#10 passed!" || true
+echo "- 5%  2 +2-6 / 2" | ./${PROG} | cmp <(echo "-2") && echo "test#11 passed!" || true
+
+make clean