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Stack Diagram: 
Expression1 Symbol2 Expression3

This operation takes an expression and a symbol. It then searches for that symbol in that expression. The first instance of that symbol it finds in the expression is then isolated. If isolating X in the expression 'X+Y=Z', the result will be 'Z-Y'. That means the first instance of X in the expression is equal to 'Z-Y'. If the expression does not contain an "=" operation, then an implied "=0" is appended to the end of the expression.

If there is only one instance of that symbol in the expression, then the result will be an expression which contains no instances of the isolated symbol. On the other hand, if there are more than one instance of the symbol in the expression, then the result will include the symbol being isolated. For example, if 'X+Y+X=Z' is isolated for X, the result will be 'Z-X-Y'.

The expression must only contain operations which have an inverse. Each operation in this reference which has an inverse is labelled with "Invertible: Yes". Some inverse functions are periodic. In these cases, a "n1", "n2", etc symbol is inserted into the result. The "n#" symbol should be set to any integer variable (positive, negative or zero) to evaluate for a specific periodic value. In some cases, the inverse has a positive or negative result. In this case a "s1", "s2", etc symbol is inserted into the result. This variable should be set to one to evaluate the positive result or minus 1 to evaluate the negative result.

The result is also evaluated (see the EVAL operation for information about what is done during evaluation) before it is pushed onto the stack. If all symbols have real values, the result could be a real number.