Ask Your Question

Revision history [back]

click to hide/show revision 1
initial version

How to recursively substitute from global name space?

In sage 3.x, I used the below function to automatically substitute into an expression all assignments I have made previously. How can I get it to work in Sage 5.x or is there a better way now?

def subsg(variable, *args):
    Substitutes all definitions in the global name space for the variables contained in 'variable' and returns the result.
        variable -- a symbolic variable
        *args -- an optional dictionary containing additional parameter definitions
        sage: var ('a b c d')
        a b c
        sage: f = a*x
        sage: a = 2*b
        sage: b = c^2
        sage: cons1 = dict(c = d^3)
        sage: subsg(f,cons1)
    Or, if cons1 is not to be used:
        sage: subsg(f)

    expr1 = variable
    expr2 = variable.subs(globals()).subs(*args)
    while expr1 <> expr2:
        expr1 = expr2
        expr2 = expr1.subs(globals()).subs(*args)
    return expr1