add units converter

Author: mdoege

README.md

@@ -1,15 +1,22 @@
 ## PyCalc, a collection of simple calculators in PyGame
 
-Three scientific calculators (using binary internally):
+### Overview
 
-    pycalc_light, pycalc_dark, pycalc_lcars
+Four scientific calculators (using binary numbers internally):
 
-Four-function calculator (using decimal internally, based on Python's *decimal* module):
+* pycalc_light (light theme)
+* pycalc_dark (dark theme)
+* pycalc_lcars (LCARS theme)
+* pycalc_units (converts from US units to metric units, e.g. to l, m, m², and kg)
 
-    pycalc_desk
+There is also pycalc_desk, a four-function calculator using decimal internally, based on Python's *decimal* module.
+
+### Usage
 
 The **decimal calculator** is useful to avoid the rounding errors of the binary calculators due to their decimal➜binary➜decimal conversions, which is better for e.g. financial calculations. It also has memory (M+ to add, MR to recall value, AC to clear) and the comma is used as a decimal separator in results.
 
+For the **unit converter**, just attach the unit to the numerical value. E.g. to convert 1.5 quarts to liters, use "1.5_qt". If you would like to _divide_ by a value, put the number and unit in parentheses, e.g. "(1.5_qt)", otherwise the result will be wrong!
+
 The **scientific calculators** work the same as the Python math module in interactive mode:
 
 * They use binary numbers internally, not decimal, so it has the usual rounding errors when comparing its results to a decimal calculator, e.g. "0.1 + 0.2" does not evaluate to exactly 0.3.
@@ -43,6 +50,8 @@ The hex buttons (a to f) and "j" can also be used as these predefined variables
 
 ![screenshot3](pycalc3.png "PyCalc screenshot (decimal version)")
 
+![screenshot3](pycalc4.png "PyCalc screenshot (units converter)")
+
 ### License
 
 Public Domain / CC0

pycalc4.png

@@ -0,0 +1,175 @@
+#!/usr/bin/env python
+
+# Python calculator for conversion to SI units
+
+import pygame
+from math import *
+
+BACKGROUND = 255, 255, 255
+BORDER = 2
+RES = 600,495           # initial window size
+HSIZE, VSIZE = 6, 9     # button grid dimension (top row is for display)
+MAXLEN = 100            # maximum digits
+
+# font name
+fn = "fsex2.ttf"
+
+us_units = (
+("_floz", "*0.0295735295625"),  # l
+("_pt",   "*0.473176473"),      # l
+("_qt",   "*0.946352946"),      # l
+("_gal",  "*3.785411784"),      # l
+("_nm",   "*1852"),             # m
+("_in",   "*0.0254"),           # m
+("_ft",   "*0.3048"),           # m
+("_sqft", "*0.09290304"),       # m²
+("_acre", "*4046.8564224"),     # m²
+("_yd",   "*0.9144"),           # m
+("_mi",   "*1609.344"),         # m
+("_lb",   "*0.45359237"),       # kg
+)
+
+# button layout
+bmap = """_in    _ft  _yd  _mi  **    C
+          _gal   exp( sin( cos( tan(  log10(
+          _pt    pi   abs( **2  sqrt( log(
+          _qt    deg( SCI  (    )     /
+          _floz  rad( 7    8    9     *
+          _sqft  fah( 4    5    6     -
+          _acre  cel( 1    2    3     +
+          _nm    _lb  0    .    j     ="""
+
+# color indices for buttons
+col_ind = """333312
+311111
+311111
+311114
+315554
+315554
+315554
+335554"""
+
+col_ind = col_ind.splitlines()
+
+# RGB colors for each color index
+cols = (
+(255, 255, 255),
+(255,96,117),
+(255,237,83),
+(142,148,255),
+(228,142,215),
+(159,229,110),
+)
+
+# text colors and sizes
+button_rgb  = 0, 0, 0
+display_rgb = 0, 0, 0
+size_button = 30
+size_disp   = 55
+
+but = []
+for l in bmap.splitlines():
+    bb = l.split()
+    but.append(bb)
+
+def deg(x):
+    return degrees(x)
+
+def rad(x):
+    return radians(x)
+
+def fah(x):
+    # Celsius -> Fahrenheit
+    return (x * 9/5) + 32
+
+def cel(x):
+    # Fahrenheit -> Celsius
+    return (x - 32) * 5/9
+
+class PyCalc:
+    def __init__(self):
+        pygame.init()
+        self.res = RES
+        self.screen = pygame.display.set_mode(self.res, pygame.RESIZABLE)
+        pygame.display.set_caption('PyCalc (units)')
+        self.screen.fill(BACKGROUND)
+        self.font = pygame.font.Font(fn, size_button)
+        self.fontres = pygame.font.Font(fn, size_disp)
+        self.clock = pygame.time.Clock()
+        self.inp = ""
+
+    def events(self):
+        global a, b
+
+        for event in pygame.event.get():
+            if event.type == pygame.QUIT: self.running = False
+            if event.type == pygame.VIDEORESIZE:
+                self.res = event.w, event.h
+                self.last = 0
+                self.screen = pygame.display.set_mode(self.res, pygame.RESIZABLE)
+            if event.type == pygame.MOUSEBUTTONDOWN:
+                x, y = pygame.mouse.get_pos()
+                boxx, boxy = self.res[0] // HSIZE, self.res[1] // VSIZE
+                X, Y = x // boxx, y // boxy
+                if Y == 0 or Y > VSIZE - 1 or X > HSIZE - 1:
+                    return
+                ci = but[Y - 1][X]
+                if ci == "=":       # evaluate expression
+                    try:
+                        inp2 = self.inp
+                        for u1, u2 in us_units:
+                            inp2 = inp2.replace(u1, u2)
+                        self.inp = str(eval(inp2))
+                        a = eval(self.inp)
+                    except:
+                        self.inp += " *ERROR*"
+                elif ci == "C":     # clear screen
+                    self.inp = ""
+                elif ci == "SCI":   # convert to scientific notation
+                    try:
+                        self.inp = "%e" % float(self.inp)
+                    except:
+                        pass
+                else:               # or add button text to input
+                    self.inp += but[Y - 1][X]
+
+    def run(self):
+        self.running = True
+        while self.running:
+            self.clock.tick(10)
+            self.events()
+            self.update()
+        pygame.quit()
+
+    def update(self):
+        self.screen.fill(BACKGROUND)
+        boxx, boxy = self.res[0] // HSIZE, self.res[1] // VSIZE
+        for y in range(1, VSIZE):
+            for x in range(HSIZE):
+                ci = int(col_ind[y - 1][x])
+                pygame.draw.rect(self.screen, cols[ci],
+                    [x * boxx + BORDER, y * boxy + BORDER,
+                    boxx - 2 * BORDER, boxy - 2 * BORDER])
+                t = but[y - 1][x]
+                if t[-1] == "(" and t != "(":
+                    t = t[:-1]
+                if t != "#":
+                    tr = self.font.render(t, True, button_rgb)
+                    ox = max(0, (boxx - tr.get_width()) // 2)
+                    oy = max(0, (boxy - tr.get_height()) // 2)
+                    self.screen.blit(tr, (x * boxx + BORDER + ox, y * boxy + BORDER + oy))
+        if len(self.inp) < MAXLEN:  # check if maximum digits exceeded
+            t = self.inp
+        else:
+            try:
+                self.inp = "%e" % float(self.inp)
+                t = self.inp
+            except:
+                t = "*TOO LONG*"
+        tr = self.fontres.render(t, True, display_rgb)
+        self.screen.blit(tr, (0, 0))
+        pygame.display.flip()
+
+app = PyCalc()
+app.run()
+