Re: Replace list element based on a condition how to
- To: mathgroup at smc.vnet.net
- Subject: [mg106747] Re: Replace list element based on a condition how to
- From: Bill Rowe <readnews at sbcglobal.net>
- Date: Fri, 22 Jan 2010 05:40:26 -0500 (EST)
On 1/21/10 at 4:53 AM, canopus56 at yahoo.com (Canopus56) wrote: >Another newbie type question. Several responders recommended: >>In[18]:= lst1 /. n_Integer :> fncHourFix[n] >Q1. What is the "_Integer" part of "n_Integer"? This and more is answered in the documentation. See tutorial/PatternsOverview for various details about patterns and pattern matching. For a the specific answer to the question above, see the fourth entry which can be directly accessed as tutorial/Spec= ifyingTypesOfExpressionInPatterns >Is that just declaring a variable name "n_Integer" or is that a way >to declare a datatype "Integer". Neither is quite accurate. The pattern n_h has three parts, n a local name for what ever is matched by the pattern, _ essentially a place holder h the head of the thing to be matched. So, n_Integer will match anything with Head = Integer and give it a local name n. This isn't really the same as declaring n to be an integer as you might do in say C or some other computer programming language. >If that syntax is a way to declare a datatype, where is that >referenced in Mathematica documentation? I really scoured the >Documentation trying to find how to force a datatype, e.g. - VBA's >equivalent to CStr, CDbl, CInt, etc. As far as I know, there is no Mathematica syntax for declaring the datatype of variables.
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