RE : Building List

• To: mathgroup at smc.vnet.net
• Subject: [mg48033] RE : [mg48015] Building List
• From: "Florian Jaccard" <florian.jaccard at eiaj.ch>
• Date: Sat, 8 May 2004 01:23:37 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```Hello !

There are a lot of ways...

For example :

In[47]:=
exemple = {{1, 2}, {3, 4, 5, 6}, {7, 8}, {9, 10, 11}};

In[52]:=
Clear[f];
f[li_ /; Length[li] > 2] := ({First[li], #1} & ) /@
Drop[li, 1];
f[li_] := {li};

In[55]:=
Flatten[f /@ exemple, 1]

Out[55]=
{{1, 2}, {3, 4}, {3, 5}, {3, 6}, {7, 8}, {9, 10},
{9, 11}}

Meilleures salutations

F.Jaccard

-----Message d'origine-----
De : Bruce W. Colletti [mailto:bcolletti at compuserve.com]
Envoyé : vendredi, 7. mai 2004 10:30
À : mathgroup at smc.vnet.net
Objet : [mg48015] Building List

Re Mathematica 5.0.1.0.

I have a list of lists -- e.g., L = { {1,2},{3,4,5,6},{7,8} } -- and
want to replace element-lists (whose length exceeds 2) with another list
built from that element.  All else is untouched.

For instance, using L above, replace {3,4,5,6} with {3,4}, {3,5}, {3,6}.
This transforms L to the desired form { {1,2}, {3,4}, {3,5}, {3,6},
{7,8} }.

Although I can do this using Sow and Reap, am hoping there's an easier
way using rules (/.).  In general, I want to replace those L-elements x
(that meet a criterion) with foo[x].

Thanks.

Bruce

```

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