From 21210c5c072ddd174f91bd7c80a1b2a00cb39bf3 Mon Sep 17 00:00:00 2001
From: Daniel Thompson <daniel@redfelineninja.org.uk>
Date: Mon, 28 Dec 2020 14:41:37 +0000
Subject: [PATCH] apps: calc: Rewrite the display and calculation engine

Currently calculations such as 22/7 do not work correctly on the
simulator (which uses double precision floating point). Fix this
by explicitly truncating the strings when needed.

Additionally the current calculate() method has some problems when
the calculation cannot be evaluated since it will needlessly clear out
the calculation. Push calculate (and the exception handling) into the
caller and report errors using the vibration motor instead.

Finally we rename display_output() to the more idiomatic _update().

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
---
 wasp/apps/calc.py | 34 ++++++++--------------------------
 1 file changed, 8 insertions(+), 26 deletions(-)

diff --git a/wasp/apps/calc.py b/wasp/apps/calc.py
index 5860b31..e5ea04d 100644
--- a/wasp/apps/calc.py
+++ b/wasp/apps/calc.py
@@ -74,10 +74,13 @@ class CalculatorApp():
             if (button_pressed == "C"):
                 self.output = ""
             elif (button_pressed == "="):
-                self.output = self.calculate(self.output)
+                try:
+                    self.output = str(eval(self.output.replace('^', '**')))[:12]
+                except:
+                    wasp.watch.vibrator.pulse()
             else:
                 self.output +=  button_pressed
-        self.display_output()
+        self._update()
 
     def _draw(self):
         draw = wasp.watch.drawable
@@ -106,27 +109,6 @@ class CalculatorApp():
         draw.string("<", 215, 10)
         draw.set_color(wasp.system.theme('accent-hi'))
     
-
-
-    def display_output(self):
-        wasp.watch.drawable.fill(x=2,y=2,w=170,h=40) 
-        if (self.output != ""):
-            if len(self.output) >= 10:
-                wasp.watch.drawable.string(self.output[len(self.output)-9:], 6, 14, width=170)
-            else:
-                wasp.watch.drawable.string(self.output, 6, 14, width=170)
-
-    def calculate(self,s):
-        equation = s
-        
-        # Normal calculator stuff    
-        for i in range(len(s)):
-            if (s[i] =="^"):
-                equation = s[:i] + "**"+s[i+1:]
-            elif (s[i] == ":"):
-                equation = s[:i] + "/"+s[i+1:]
-        try:
-            result = eval(equation)
-        except: # Error
-            result = ""
-        return str(result)
\ No newline at end of file
+    def _update(self):
+        output = self.output if len(self.output) < 12 else self.output[len(self.output)-12:]
+        wasp.watch.drawable.string(output, 0, 14, width=200, right=True)