DSTV: Datashape & -type Verification

Enables reflective data verification.

Solves the common problem of massive branching (if-then-elseif-...-end) and repetetive error condition statments by introducing a simple reflective mechanism in programming techniques.

The well known verification functions NARGCHK and NARGOUTCHK return an appropiate error message, if the number of in- resp outputs is not correct.

The ARGCHK function also returns an appropiate error message, but the clue is, the error condition is the message. Therefore any expression evaluatable to a logical condition may be error condition an error message at once.

Brief Example
error(argchk('isnumeric(X)'))
ARGCHK returns the message MSG = '~isnumeric(X)' and ERROR displays MSG and aborts function, if X is not numeric, otherwise ARGCHK returns an empty message MSG = '', so that ERROR takes no action.

As obvious, the power of the function is in the flexibility, to use any kind of expression evaluatable to a logical expression. Due to this any user defined logical function may be used for more understandable error messages.