From a92877403ac522d17602ae24782b44a99a268539 Mon Sep 17 00:00:00 2001
From: Eric Andersen <andersen@codepoet.org>
Date: Wed, 22 Oct 2003 11:24:39 +0000
Subject: [PATCH] Goetz Bock writes:

Dear list,

during my quest do pack busybox into an RPM, I've fixed a small bug
(missing \n) in dc's usage. And added two additional operations: mod and
exp/power.

Feel free to drop them.
---
 include/usage.h |  6 ++++--
 miscutils/dc.c  | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/usage.h b/include/usage.h
index 851023e..268c23c 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -280,8 +280,10 @@
 	"expression ..."
 #define dc_full_usage \
 	"This is a Tiny RPN calculator that understands the\n" \
-	"following operations: +, -, /, *, and, or, not, eor.\n" \
-	"i.e., 'dc 2 2 add' -> 4, and 'dc 8 8 \\* 2 2 + /' -> 16" \
+	"following operations: +, add, -, sub, *, mul, /, div, %, mod, "\
+	"**, exp, and, or, not, eor.\n" \
+	"For example: 'dc 2 2 add' -> 4, and 'dc 8 8 \\* 2 2 + /' -> 16.\n" \
+	"\nOptions:\n" \
 	"p - Prints the value on the top of the stack, without altering the stack.\n" \
 	"f - Prints the entire contents of the stack without altering anything.\n" \
 	"o - Pops the value off the top of the stack and uses it to set the output radix.\n" \
diff --git a/miscutils/dc.c b/miscutils/dc.c
index 451423c..f574ae4 100644
--- a/miscutils/dc.c
+++ b/miscutils/dc.c
@@ -44,6 +44,13 @@ static void mul(void)
 	push(pop() * pop());
 }
 
+static void power(void)
+{
+	double topower = pop();
+
+	push(pow(pop(), topower));
+}
+
 static void divide(void)
 {
 	double divisor = pop();
@@ -51,6 +58,13 @@ static void divide(void)
 	push(pop() / divisor);
 }
 
+static void mod(void)
+{
+	unsigned int d = pop();
+
+	push((unsigned int) pop() % d);
+}
+
 static void and(void)
 {
 	push((unsigned int) pop() & (unsigned int) pop());
@@ -119,10 +133,16 @@ static const struct op operators[] = {
 	{"mul", mul},
 	{"/",   divide},
 	{"div", divide},
+	{"**",  power},
+	{"exp", power},
+	{"pow", power},
+	{"%",   mod},
+	{"mod", mod},
 	{"and", and},
 	{"or",  or},
 	{"not", not},
 	{"eor", eor},
+	{"xor", eor},
 	{"p", print_no_pop},
 	{"f", print_stack_no_pop},
 	{"o", set_output_base},
-- 
2.7.4