Expression1 | Symbol2 | → | Expression3 |
This operation takes an expression and a target symbol. It then recursively evaluates the value of each symbol in the expression to see if that symbol can be replaced with an expression which contains the target symbol. If the symbol in the expression can be be expressed in terms of the target symbol, then it is left unchanged.
As an example, if the symbol X has value 'A+B' and Y has value 'C+D', then if SHOW is executed on the expression 'X+Y' with a target symbol B, the result will be 'A+B+Y'.