From 9064811c32218ee1a4adbdb3431d747836bd9bdf Mon Sep 17 00:00:00 2001
From: tomsmeding <tom.smeding@gmail.com>
Date: Sat, 8 Oct 2016 11:58:01 +0200
Subject: Bigint parsing: also hex, and add string constructor

---
 bigint.cpp | 42 ++++++++++++++++++++++++++++++++++++------
 bigint.h   |  1 +
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/bigint.cpp b/bigint.cpp
index 98846e0..72a882b 100644
--- a/bigint.cpp
+++ b/bigint.cpp
@@ -1,4 +1,5 @@
 #include <iomanip>
+#include <sstream>
 #include <stdexcept>
 #include <cctype>
 #include <cassert>
@@ -15,6 +16,10 @@ Bigint Bigint::two(2);
 Bigint::Bigint()
 	:sign(1){}
 
+Bigint::Bigint(const string &repr){
+	stringstream(repr)>>*this;
+}
+
 Bigint::Bigint(slongdigit_t v)
 	:digits(1,abs(v)),sign(v>=0?1:-1){
 	static_assert(sizeof(longdigit_t)==2*sizeof(digit_t),
@@ -573,23 +578,48 @@ istream& operator>>(istream &is,Bigint &b){
 	while(isspace(is.peek()))is.get();
 	if(!is)return is;
 	b.digits.resize(0);
-	b.sign=1;
-	Bigint ten(10);
+	if(is.peek()=='-'){
+		b.sign=-1;
+		is.get();
+	} else b.sign=1;
 	bool acted=false;
+	if(is.peek()=='0'){
+		is.get();
+		if(is.peek()=='x'){
+			is.get();
+			acted=false;
+			while(true){
+				char c=is.peek();
+				if(!isdigit(c)&&(c<'a'||c>'f')&&(c<'A'||c>'F'))break;
+				acted=true;
+				is.get();
+				if(!is)break;
+				int n;
+				if(c<='9')n=c-'0';
+				else if(c<='F')n=c-'A'+10;
+				else n=c-'a'+10;
+				b<<=4;
+				b+=n;
+			}
+			if(!acted)is.setstate(ios_base::failbit);
+			b.normalise();
+			b.checkconsistent();
+			return is;
+		} else acted=true;
+	}
+	Bigint ten(10);
 	while(true){
 		char c=is.peek();
 		if(!isdigit(c))break;
 		acted=true;
 		is.get();
-		if(!is){
-			b.checkconsistent();
-			return is;
-		}
+		if(!is)break;
 		b*=ten;
 		b+=c-'0';
 		// cerr<<"b="<<b<<endl;
 	}
 	if(!acted)is.setstate(ios_base::failbit);
+	b.normalise();
 	b.checkconsistent();
 	return is;
 }
diff --git a/bigint.h b/bigint.h
index bd15fd9..4d6c980 100644
--- a/bigint.h
+++ b/bigint.h
@@ -32,6 +32,7 @@ public:
 	Bigint();
 	Bigint(const Bigint&)=default;
 	Bigint(Bigint&&)=default;
+	explicit Bigint(const std::string&);
 	explicit Bigint(sdigit_t);
 	explicit Bigint(digit_t);
 	explicit Bigint(slongdigit_t);
-- 
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