Re: HoldFirst confusion
- To: mathgroup at smc.vnet.net
- Subject: [mg65537] Re: HoldFirst confusion
- From: Jon Harrop <usenet at jdh30.plus.com>
- Date: Thu, 6 Apr 2006 06:53:16 -0400 (EDT)
- References: <e1095n$lkf$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Yaroslav Bulatov wrote: > The following gives an error > f = 5; f[a_] = a > > Set is HoldFirst, so why does it evaluate it's first argument f[a_]? Conversely, why do the attributes of Set and SetDelayed indicate that they hold their first argument when the kernel evaluates it. On a related note, how can you define and use a downvalue that matches g[1+2] without evaluating the 1+2? -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/products/ocaml_for_scientists/chapter1.html
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