From b6c2a21ecd587bb3918d07ea8189ff1e41609cf3 Mon Sep 17 00:00:00 2001
From: Yuriy Lazarev <unisay@gmail.com>
Date: Sun, 24 Sep 2017 17:30:42 +0200
Subject: [PATCH] toBase :: Int -> BigInt -> String

---
 src/Data/BigInt.js   |  7 ++++---
 src/Data/BigInt.purs |  7 ++++++-
 test/Main.purs       | 18 +++++++++++-------
 3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/Data/BigInt.js b/src/Data/BigInt.js
index 4eaa776..36567ed 100644
--- a/src/Data/BigInt.js
+++ b/src/Data/BigInt.js
@@ -19,8 +19,10 @@ exports["fromBase'"] = function(just) {
 
 exports.fromInt = bigInt;
 
-exports.toString = function(x) {
-  return x.toString();
+exports.toBase = function(base) {
+  return function (x) {
+    return x.toString(base);
+  };
 };
 
 exports.toNumber = function(x) {
@@ -124,4 +126,3 @@ exports.shr = function(x) {
     return x.shiftRight(n);
   };
 };
-
diff --git a/src/Data/BigInt.purs b/src/Data/BigInt.purs
index cf23fc6..7d3aff7 100644
--- a/src/Data/BigInt.purs
+++ b/src/Data/BigInt.purs
@@ -5,6 +5,7 @@ module Data.BigInt
   , fromBase
   , fromInt
   , toString
+  , toBase
   , abs
   , even
   , odd
@@ -112,7 +113,11 @@ instance ordBigInt :: Ord BigInt where
                   _ -> LT
 
 -- | A decimal representation of the `BigInt` as a `String`.
-foreign import toString :: BigInt -> String
+toString :: BigInt -> String
+toString = toBase 10
+
+-- | A base N representation of the `BigInt` as a `String`.
+foreign import toBase :: Int -> BigInt -> String
 
 instance showBigInt :: Show BigInt where
   show x = "fromString \"" <> toString x <> "\""
diff --git a/test/Main.purs b/test/Main.purs
index 486d738..2fdd838 100644
--- a/test/Main.purs
+++ b/test/Main.purs
@@ -5,7 +5,7 @@ import Control.Monad.Eff.Console (CONSOLE, log)
 import Control.Monad.Eff.Exception (EXCEPTION)
 import Control.Monad.Eff.Random (RANDOM)
 import Data.Array (filter, range)
-import Data.BigInt (BigInt, abs, fromInt, prime, pow, odd, even, fromString, toNumber, fromBase, toString, not, or, xor, and, shl, shr)
+import Data.BigInt (BigInt, abs, fromInt, prime, pow, odd, even, fromString, toNumber, fromBase, toBase, toString, not, or, xor, and, shl, shr)
 import Data.Foldable (fold)
 import Data.Int as Int
 import Data.Maybe (Maybe(..), fromMaybe)
@@ -31,10 +31,10 @@ runSmallInt (SmallInt n) = n
 -- | Arbitrary instance for BigInt
 newtype TestBigInt = TestBigInt BigInt
 derive newtype instance eqTestBigInt :: Eq TestBigInt
-derive newtype instance ordTestBigInt :: Ord TestBigInt                        
+derive newtype instance ordTestBigInt :: Ord TestBigInt
 derive newtype instance semiringTestBigInt :: Semiring TestBigInt
 derive newtype instance ringTestBigInt :: Ring TestBigInt
-derive newtype instance commutativeRingTestBigInt :: CommutativeRing TestBigInt                        
+derive newtype instance commutativeRingTestBigInt :: CommutativeRing TestBigInt
 derive newtype instance euclideanRingTestBigInt :: EuclideanRing TestBigInt
 
 instance arbitraryBigInt :: Arbitrary TestBigInt where
@@ -80,6 +80,11 @@ main = do
   assert $ fromBase 2 "100" == Just four
   assert $ fromBase 16 "ff" == fromString "255"
 
+  log "Rendering bigints as strings with a different base"
+  assert $ toBase 2 four == "100"
+  assert $ (toBase 16 <$> fromString "255") == Just "ff"
+  assert $ toString (fromInt 12345) == "12345"
+
   log "Conversions between String, Int and BigInt should not loose precision"
   quickCheck (\n -> fromString (show n) == Just (fromInt n))
   quickCheck (\n -> Int.toNumber n == toNumber (fromInt n))
@@ -124,12 +129,11 @@ main = do
   log "Shifting"
   assert $ shl two one == four
   assert $ shr two one == one
-  
+
   let prxBigInt = Proxy ∷ Proxy TestBigInt
   Data.checkEq prxBigInt
   Data.checkOrd prxBigInt
-  Data.checkSemiring prxBigInt  
+  Data.checkSemiring prxBigInt
   Data.checkRing prxBigInt
---  Data.checkEuclideanRing prxBigInt  
+--  Data.checkEuclideanRing prxBigInt
   Data.checkCommutativeRing prxBigInt
-