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# -*- coding: utf-8 -*-
## Very simple unit support:
## - creates variable names like 'mV' and 'kHz'
## - the value assigned to the variable corresponds to the scale prefix
## (mV = 0.001)
## - the actual units are purely cosmetic for making code clearer:
##
## x = 20*pA is identical to x = 20*1e-12
## No unicode variable names (μ,Ω) allowed until python 3
SI_PREFIXES = 'yzafpnum kMGTPEZY'
UNITS = 'm,s,g,W,J,V,A,F,T,Hz,Ohm,S,N,C,px,b,B'.split(',')
allUnits = {}
def addUnit(p, n):
g = globals()
v = 1000**n
for u in UNITS:
g[p+u] = v
allUnits[p+u] = v
for p in SI_PREFIXES:
if p == ' ':
p = ''
n = 0
elif p == 'u':
n = -2
else:
n = SI_PREFIXES.index(p) - 8
addUnit(p, n)
cm = 0.01
def evalUnits(unitStr):
"""
Evaluate a unit string into ([numerators,...], [denominators,...])
Examples:
N m/s^2 => ([N, m], [s, s])
A*s / V => ([A, s], [V,])
"""
pass
def formatUnits(units):
"""
Format a unit specification ([numerators,...], [denominators,...])
into a string (this is the inverse of evalUnits)
"""
pass
def simplify(units):
"""
Cancel units that appear in both numerator and denominator, then attempt to replace
groups of units with single units where possible (ie, J/s => W)
"""
pass
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