Substituting a variable by a value

9.1.12 Substituting a variable by a value

The | operator is an infixed operator that evaluates an expression after giving values to some variables. It does not evaluate the expression before the variables are replaced by the requested values.

| is an infixed operator, hence it takes two arguments:
- expr, an expression depending on one or more variables on the left hand side.
- x₁=a₁, ldots; an equality or sequence of several equalities.
expr|x₁=a₁,… returns the expression expr with x₁ replaced by a₁, etc.

Examples

The command lines below work even if a and/or b have been assigned.

a^2+1 | a=2

a^2+b | a=2,b=3