From 18f81a336db495b5e468837caf8560c14aea6a19 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Alexis=20Laferri=C3=A8re?= <alexis.laf@xymus.net>
Date: Sun, 1 May 2016 15:11:14 -0400
Subject: [PATCH] calculator: extend the calculator logic with scientific
 operators
MIME-Version: 1.0
Content-Type: text/plain; charset=utf8
Content-Transfer-Encoding: 8bit

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
---
 examples/calculator/src/calculator_logic.nit |   90 ++++++++++++++++++++------
 1 file changed, 71 insertions(+), 19 deletions(-)

diff --git a/examples/calculator/src/calculator_logic.nit b/examples/calculator/src/calculator_logic.nit
index 46f9ca3..775e8e3 100644
--- a/examples/calculator/src/calculator_logic.nit
+++ b/examples/calculator/src/calculator_logic.nit
@@ -24,33 +24,35 @@ class CalculatorContext
 	# Result of the last operation
 	var result: nullable Numeric = null
 
-	# Last operation pushed with `push_op`, to be executed on the next push
+	# Last operation pushed with `push_op`
 	var last_op: nullable Text = null
 
+	# Is `last_op` an unary operation or a '='?
+	var last_op_was_unary = false
+
 	# Value currently being entered
 	var current: nullable String = null
 
 	# Text to display on screen
 	fun display_text: String
 	do
-		var result = result
-		var last_op = last_op
-		var current = current
-
 		var buf = new FlatBuffer
 
-		if result != null and (current == null or last_op != "=") then
-			if last_op == "=" then buf.append "= "
+		var last_op = last_op
+		var result = result
+		if result != null then
+			if last_op_was_unary then buf.append "{last_op or else "?"} "
 
 			buf.append result.to_s
 			buf.add ' '
 		end
 
-		if last_op != null and last_op != "=" then
+		if last_op != null and not last_op_was_unary then
 			buf.append last_op
 			buf.add ' '
 		end
 
+		var current = current
 		if current != null then
 			buf.append current.to_s
 			buf.add ' '
@@ -62,30 +64,74 @@ class CalculatorContext
 	# Push operation `op`, will usually execute the last operation
 	fun push_op(op: Text)
 	do
+		# Constants
+		# TODO Protect constants to preserve full precision and to forbid appending extra digits
+		if op == "π" then
+			if last_op_was_unary then clear
+			current = pi.to_s
+			return
+		else if op == "e" then
+			if last_op_was_unary then clear
+			current = 2.718282.to_s
+			return
+
+		# Clear screen
+		else if op == "C" then
+			clear
+			return
+		end
+
+		# For all operators, apply pending operators
 		apply_last_op_if_any
-		if op == "C" then
-			self.result = null
-			last_op = null
+
+		var result = self.result or else 0
+
+		last_op = op
+		last_op_was_unary = true
+
+		# Unary operators
+		if op == "√" then
+			self.result = result.to_f.sqrt
+		else if op == "x²" then
+			self.result = result.to_f.pow(2.0)
+		else if op == "x!" then
+			self.result = result.to_i.factorial
+		else if op == "sin" then
+			self.result = result.to_f.sin
+		else if op == "cos" then
+			self.result = result.to_f.cos
+		else if op == "tan" then
+			self.result = result.to_f.tan
+
+		# =
+		else if op == "=" then
+			current = null
+
+		# Binary operators
 		else
-			last_op = op # store for next push_op
+			self.result = result # Set as same or 0
+			last_op_was_unary = false
+			current = null
 		end
+	end
 
-		# prepare next current
-		self.current = null
+	# Clear all state
+	private fun clear
+	do
+		result = null
+		last_op = null
+		current = null
 	end
 
 	# Push a digit
 	fun push_digit(digit: Int)
 	do
+		if last_op_was_unary then clear
+
 		var current = current
 		if current == null then current = ""
 		current += digit.to_s
 		self.current = current
-
-		if last_op == "=" then
-			self.result = null
-			last_op = null
-		end
 	end
 
 	# Switch entry mode from integer to decimal
@@ -118,6 +164,12 @@ class CalculatorContext
 				result = result.div(current.to_n)
 			else if op == "*" or op == "×" then
 				result = result.mul(current.to_n)
+			else if op == "%" then
+				result = result.to_i % current.to_i
+			else if op == "xⁿ" then
+				result = result.to_f.pow(current.to_f)
+			else if op == "log" then
+				result = result.to_f.log_base(current.to_f)
 			end
 		end
 
-- 
1.7.9.5