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

**Follow-Ups**:**Re: Re: HoldFirst confusion***From:*"Carl K. Woll" <carlw@wolfram.com>

**Re: Re: HoldFirst confusion***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>