Function: at (<expr>, [<eqn_1>, ..., <eqn_n>])
Function: at (<expr>, <eqn>) Evaluates the expression <expr> with the variables assuming the values as specified for them in the list of equations
[<eqn_1>, ..., <eqn_n>] or the single equation <eqn>.
If a subexpression depends on any of the variables for which a value is specified but there is no atvalue specified and it cant be otherwise evaluated, then a noun form of the
at is returned which displays in a two-dimensional form.
at carries out multiple substitutions in series, not parallel.
atvalue. For other functions which carry out substitutions, see also
(%i1) atvalue (f(x,y), [x = 0, y = 1], a^2); 2 (%o1) a (%i2) atvalue (diff (f(x,y), x), x = 0, 1 + y); (%o2) @2 + 1 (%i3) printprops (all, atvalue); ! d ! --- (f(@1, @2))! = @2 + 1 d@1 ! !@1 = 0
2 f(0, 1) = a
(%o3) done (%i4) diff (4*f(x, y)^2 - u(x, y)^2, x); d d (%o4) 8 f(x, y) (-- (f(x, y))) - 2 u(x, y) (-- (u(x, y))) dx dx (%i5) at (%, [x = 0, y = 1]); ! 2 d ! (%o5) 16 a - 2 u(0, 1) (-- (u(x, y))! ) dx ! !x = 0, y = 1
There are also some inexact matches for
?? at to see them.
(%o1) true (%i2)