Re: Not accepting function as parameter

*To*: mathgroup at smc.vnet.net*Subject*: [mg71697] Re: Not accepting function as parameter*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Mon, 27 Nov 2006 04:03:59 -0500 (EST)*Organization*: The Open University, Milton Keynes, UK*References*: <ekbmj4$f87$1@smc.vnet.net>

wooks wrote: > This is a piece of experimental code. The function happy does not > evaluate whenever I pass f as a parameter as in the example below. > > Clear[happy] > happy[ f_Function, a_Integer, b_Integer] := Module[{width = (b - > a)/1000}, > f[width]]; > > happy[ Sin, 1, 21] > > I'd be grateful for help. > The issue is that built-in mathematical functions such as Sin, Cos, Log, etc, have _Symbol_ for head and not _Function_. On the other hand, pure function have _Function_ for head. You can test the head of any Mathematica expression with /Head/ (See below for an example.) Therefore, you must add an alternative condition to the pattern f to take in account both possibilities. In[1]:= Head[Sin] Out[1]= Symbol In[2]:= Head[#1^2 & ] Out[2]= Function In[3]:= Clear[happy] happy[(f_Symbol) | (f_Function), a_Integer, b_Integer] := Module[{width = (b - a)/1000}, f[width]]; happy[Sin, 1, 21] happy[#1^2 & , 1, 21] happy[N[#1^2] & , 1, 21] Out[5]= Sin[1/50] Out[6]= 1/2500 Out[7]= 0.0004 HTH, Jean-Marc