From fb1f8d3a02908e2fe8c08924c2eacef6b84a7204 Mon Sep 17 00:00:00 2001
From: Raymond Hogenson <rhogenson@posteo.net>
Date: Fri, 18 May 2018 12:01:22 -0800
Subject: Support exponentiation

Haskell might make this overcomplicated, but it's a complicated problem
to solve, I suppose. Whatever. It works well.
---
 Expr.hs     | 2 ++
 RealCalc.hs | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/Expr.hs b/Expr.hs
index 2210735..6e12a87 100644
--- a/Expr.hs
+++ b/Expr.hs
@@ -30,6 +30,7 @@ data Expr = Plus Expr Expr
           | Minus Expr Expr
           | Times Expr Expr
           | Div Expr Expr
+          | Pow Expr Expr
           | EInt Integer
           | EFloat Double
           | E
@@ -66,6 +67,7 @@ prefix name fun = Prefix (fun <$ tokenS name)
 table :: [[Operator String u Data.Functor.Identity.Identity Expr]]
 table = [ [ prefix "log" Log, prefix "sin" Sin, prefix "cos" Cos, prefix "sqrt" Sqrt ]
         , [ prefix "-" Negate ]
+        , [ binary "^" Pow AssocLeft ]
         , [ binary "*" Times AssocLeft
           , binary "/" Div AssocLeft
           ]
diff --git a/RealCalc.hs b/RealCalc.hs
index 11eebe4..df2e06d 100644
--- a/RealCalc.hs
+++ b/RealCalc.hs
@@ -54,6 +54,12 @@ simplify (Expr.Times e1 e2) =
   genericCombine (*) (simplify e1) (simplify e2)
 simplify (Expr.Div e1 e2) =
   RFloat (rToDouble (simplify e1) / rToDouble (simplify e2))
+simplify (Expr.Pow e1 e2) =
+  case (simplify e1, simplify e2) of
+    (RInt a, RInt b)
+      | b >= 0 -> RInt (a ^ b)
+    (a, RInt b) -> RFloat (rToDouble a ^^ b)
+    (a, RFloat b) -> RFloat (rToDouble a ** b)
 simplify (Expr.EInt i) = RInt i
 simplify (Expr.EFloat d) = RFloat d
 simplify Expr.E = RFloat (exp 1)
-- 
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