Chemical calculator

Chemical calculator is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

This application calculates the molar mass given a chemical formula.

The atom masses are available below.

• Grouping with ()
• Repetition

Examples

• assert 1.008 == molar_mass('H')
• assert 2.016 == molar_mass('H2')
• assert 18.015 == molar_mass('H2O')
• assert 142.03553856000002 == molar_mass('Na2SO4')
• assert 84.162 == molar_mass('C6H12')
• assert 186.29499999999996 == molar_mass('COOH(C(CH3)2)3CH3')

Python

Atom masses

<lang python>ATOMIC_MASS = { 'H':1.008, 'He':4.002602, 'Li':6.94, 'Be':9.0121831, 'B':10.81, 'C':12.011, 'N':14.007, 'O':15.999, 'F':18.998403163, 'Ne':20.1797, 'Na':22.98976928, 'Mg':24.305, 'Al':26.9815385, 'Si':28.085, 'P':30.973761998, 'S':32.06, 'Cl':35.45, 'Ar':39.948, 'K':39.0983, 'Ca':40.078, 'Sc':44.955908, 'Ti':47.867, 'V':50.9415, 'Cr':51.9961, 'Mn':54.938044, 'Fe':55.845, 'Co':58.933194, 'Ni':58.6934, 'Cu':63.546, 'Zn':65.38, 'Ga':69.723, 'Ge':72.630, 'As':74.921595, 'Se':78.971, 'Br':79.904, 'Kr':83.798, 'Rb':85.4678, 'Sr':87.62, 'Y':88.90584, 'Zr':91.224, 'Nb':92.90637, 'Mo':95.95, 'Ru':101.07, 'Rh':102.90550, 'Pd':106.42, 'Ag':107.8682, 'Cd':112.414, 'In':114.818, 'Sn':118.710, 'Sb':121.760, 'Te':127.60, 'I':126.90447, 'Xe':131.293, 'Cs':132.90545196, 'Ba':137.327, 'La':138.90547, 'Ce':140.116, 'Pr':140.90766, 'Nd':144.242, 'Pm':145, 'Sm':150.36, 'Eu':151.964, 'Gd':157.25, 'Tb':158.92535, 'Dy':162.500, 'Ho':164.93033, 'Er':167.259, 'Tm':168.93422, 'Yb':173.054, 'Lu':174.9668, 'Hf':178.49, 'Ta':180.94788, 'W':183.84, 'Re':186.207, 'Os':190.23, 'Ir':192.217, 'Pt':195.084, 'Au':196.966569, 'Hg':200.592, 'Tl':204.38, 'Pb':207.2, 'Bi':208.98040, 'Po':209, 'At':210, 'Rn':222, 'Fr':223, 'Ra':226, 'Ac':227, 'Th':232.0377, 'Pa':231.03588, 'U':238.02891, 'Np':237, 'Pu':244, 'Am':243, 'Cm':247, 'Bk':247, 'Cf':251, 'Es':252, 'Fm':257 }</lang>

Solution

<lang python>from atomic_mass import ATOMIC_MASS

def parse(s): # 'H2O' => H 2 O result = [] pattern = i = 0 while i<len(s): if s[i].isupper(): if i+1<len(s) and s[i+1].islower(): result.append(s[i]+s[i+1]) pattern += 'A' i+=2 else: result.append(s[i]) pattern += 'A' i+=1 elif s[i].isdigit(): antal = int(s[i]) i+=1 while i<len(s) and s[i].isdigit(): antal = antal*10 + int(s[i]) i+=1 result.append(str(antal)) pattern += '1' else: result.append(s[i]) pattern += s[i] i+=1 return result,pattern

def pass1(m1,m2): # H 2 O => H * 2 + O SYMBOLS = 'A1()' matrix = [ '+*+=', # A = Atom '+x+=', # 1 = Count '=x=x', # ( '+*+='] # )

result = []

add = lambda a, b: [a, '+'] mul = lambda a, b: [a, '*'] error = lambda a, b: [] nop = lambda a, b: [a] operation = {'+': add, '*': mul, 'x': error, '=': nop}

for i in range(len(m1)-1): ch0 = m2[i] ch1 = m2[i+1] i0 = SYMBOLS.index(ch0) i1 = SYMBOLS.index(ch1) op = matrix[i0][i1] result += operation[op](m1[i],m1[i+1]) result.append(m1[-1]) return result

def pass2(tokens): # H * 2 + O => H 2 * O + ops = "+*" stack = [] result = []

for token in tokens: if token == '(': stack.append(token) elif token == ')': while len(stack) > 0: op = stack.pop() if op == '(': break result.append(op) else: if token in ops: while len(stack) > 0: op = stack[-1] if not (op in ops): break if ops.find(token) >= ops.find(op): break stack.pop() result.append(op) stack.append(token) else: result.append(token)

while len(stack) > 0: result.append(stack.pop()) return result

def pass3(rpn): # H 2 * O + => { H:2, O:1 } stack = [] for item in rpn: if item == '+': h1 = stack.pop() h2 = stack[-1] for key in h1: if key in h2: h2[key] += h1[key] else: h2[key] = h1[key] elif item == '*': antal = int(stack.pop()) hash = stack[-1] for key in hash: hash[key] *= antal elif item in ATOMIC_MASS: res = {} res[item] = 1 stack.append(res) else: stack.append(item) return stack.pop()

def pass4(atoms): # { H:2, O:1 } => 18.015 return sum([ATOMIC_MASS[key] * atoms[key] for key in atoms])

def molar_mass(molecule): atom_list,pattern = parse(molecule) infix = pass1(atom_list,pattern) rpn = pass2(infix) atoms = pass3(rpn) return pass4(atoms)

#assert 'Na 10 C O O H ( C ( C H 3 ) 2 ) 3 C H 3' == ' '.join(atom_list) #assert 'A1AAAA(A(AA1)1)1AA1' == pattern #assert 'Na * 10 + C + O + O + H + ( C + ( C + H * 3 ) * 2 ) * 3 + C + H * 3' == (' '.join(infix)) #assert 'Na 10 * C O O H C C H 3 * + 2 * + 3 * C H 3 * + + + + + + +' == ' '.join(rpn) #assert {'Na':10, 'C': 11, 'O': 2, 'H': 22} == atoms

assert 1.008 == molar_mass('H') assert 2.016 == molar_mass('H2') assert 18.015 == molar_mass('H2O') assert 142.03553856000002 == molar_mass('Na2SO4') assert 84.162 == molar_mass('C6H12') assert 186.29499999999996 == molar_mass('COOH(C(CH3)2)3CH3')</lang>