Checks a Laplace expression for correctness
| Number | Type | Compulsory | Default | Description | 
| 1 | string | Yes | Expression to be analysed | 
Expression to be analysed
Return type: real
Integer value from -1 to 4 signifying the validity of the Laplace expression.
| Value | Description | 
| } | |
| -1 | Unknown error in expression | 
| 0 | Expression is valid | 
| 1 | Syntax error in expression | 
| 2 | Mismatched parantheses in expression | 
| 4 | Expression uses an unknown function | 
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