Basic Examples

This is a simple example of how it works:
r={2,4,6,8,10,12,14};
In[]:=
s={3,5,7,9,11,13,15};
In[]:=
[◼]
AlternateElements
[r,s]
In[]:=
{2,5,6,9,10,13,14}
Out[]=
It also works with non-numeric terms:
rs={a1,"b1",c1,d1,☺,f1,"g1"};
In[]:=
ss={h2,i2,☺,"k2",l2,m2,n2};
In[]:=
[◼]
AlternateElements
[rs,ss]
In[]:=
{a1,i2,c1,k2,☺,m2,g1}
Out[]=

Scope

It also works with lists of different sizes, keeping all elements from the end of the longer list once the shorter list is exhausted:
t={2,4,6,8,10};
In[]:=
u={3,5,7,9,11,13,aa,17};
In[]:=
[◼]
AlternateElements
[t,u]
In[]:=
{2,5,6,9,10,13,aa,17}
Out[]=
[◼]
AlternateElements
[u,t]
In[]:=
{3,4,7,8,11,13,aa,17}
Out[]=
An example with a new pattern chosen:
l={2,4,6,8,a0,12,14,16,18,20,22,24};
In[]:=
m={3,5,7,9,11,13,15,17,b0,21,23,25};
In[]:=
[◼]
AlternateElements
[l,m,{1,2,2,2,1,2}]
In[]:=
{2,5,7,9,a0,13,14,17,b0,21,22,25}
Out[]=
Example using a list from a binary number as a pattern:
p={2,4,6,8,10,12,14,16,18,20,22,24,26,28,30};
In[]:=
q={3,5,7,9,11,13,15,17,19,21,23,25,27,29,31};
In[]:=
pat=2-IntegerDigits[854,2]
In[]:=
{1,1,2,1,2,1,2,1,1,2}
Out[]=
[◼]
AlternateElements
[p,q,pat]
In[]:=
{2,4,7,8,11,12,15,16,18,21,22,24,27,28,31}
Out[]=
Example of how we can use Alternate with random pattern:
g={2,4,6,8,10,12,14,16,18,20,22,24,26,28,30};
In[]:=
h={3,5,7,9,11,13,15,17,19,21,23,25,27,29,31};
In[]:=
[◼]
AlternateElements
[g,h,2-IntegerDigits[RandomInteger[{4,1000}],2]]
In[]:=
{2,5,6,8,10,13,14,17,18,20,22,25,26,29,30}
Out[]=

Possible Issues

AlternateElements only works with two lists at a time:
rz={abc,2,4,ch,let};
In[]:=
sz={3,5,7,9,bb,16,18};
In[]:=
tz={11,cc,13,14,15};
In[]:=
[◼]
AlternateElements
[sz,rz,tz,{2,1,1,1}]
In[]:=
[◼]
AlternateElements
[{3,5,7,9,bb,16,18},{abc,2,4,ch,let},{11,cc,13,14,15},{2,1,1,1}]
Out[]=

Neat Examples

Practical use of
AlternateElements
as an example of how to create hybrid ( alternated terms ) numbers between two real constants with a certain number of digits. In this example using Pi and E:
xa=Pi;
In[]:=
ya=E;
In[]:=
na=50;
In[]:=
f0=IntegerDigits@IntegerPart[N[xa*10^(na-1),na+10]];
In[]:=
g0=IntegerDigits@IntegerPart[N[ya*10^(na-1),na+10]];
In[]:=
NFromDigits@
[◼]
AlternateElements
[f0,g0]10^(na-1),na
In[]:=
3.7485828585590952383606834812596028947971490933959
Out[]=
NFromDigits@
[◼]
AlternateElements
[g0,f0]10^(na-1),na
In[]:=
2.1112916234897432354622473733725624871572673996791
Out[]=
Similar example with a nondefault pattern:
h0=RealDigits[N[xa,na+1]][[1]];
In[]:=
i0=RealDigits[N[ya,na+1]][[1]];
In[]:=
NFromDigits@
[◼]
AlternateElements
[h0,i0,{1,2,1,1,2,2}]10^na,na
In[]:=
3.7412828534590932383622834833596024947972490996959
Out[]=
NFromDigits@
[◼]
AlternateElements
[i0,h0,{2,2,1,1,1,2}]10^na,na
In[]:=