BUG: forgot to specify that exp lives in math namespace.
BUG: forgot to specify that exp lives in math namespace.

Chase had this right, but I stopped explicitly importing exp and
only import math.

chenxulong/quanteco,agutieda/QuantEcon.py,oyamad/QuantEcon.py,gxxjjj/QuantEcon.py,chenxulong/quanteco,andybrnr/QuantEcon.py,andybrnr/QuantEcon.py,mgahsan/QuantEcon.py,dingliumath/quant-econ,jviada/QuantEcon.py,dingliumath/quant-econ,oyamad/QuantEcon.py,mgahsan/QuantEcon.py,gxxjjj/QuantEcon.py,QuantEcon/QuantEcon.py,agutieda/QuantEcon.py,jviada/QuantEcon.py,QuantEcon/QuantEcon.py