Mathematica provides a facility for data-typing of function arguments. When a pattern match for an argument fails the unevaluated function is returned.
In[4]:= g[x_Integer]:=x^2; In[5]:= g[2.3] Out[5]= g[2.3]Since there are many options available in the package, it is preferable to perform parameter type checking for all arguments and options using a conditional test (/;). An appropriate error message is then output [16]. This behaviour is demonstrated with an example of incorrect input syntax, showing the close correspondence with Mathematica's own internal error messages.
In[6]:= FortranAssign[x,Pi t,AssignIndent->wrongtype]
FortranAssign::args:
The option AssignIndent did not evaluate to a string or a
positive integer.
Out[6]= FortranAssign[x, Pi t, AssignIndent -> wrongtype]
The option AssignIndent specifies an ASCII string prepended to
the output.