#!/usr/bin/env python
# coding: utf-8

# # vo005_Combinations
# In this tutorial we learn how combinations of RVecs can be built.
# 
# 
# 
# 
# **Author:** Stefan Wunsch  
# <i><small>This notebook tutorial was automatically generated with <a href= "https://github.com/root-project/root/blob/master/documentation/doxygen/converttonotebook.py">ROOTBOOK-izer</a> from the macro found in the ROOT repository  on Wednesday, April 17, 2024 at 11:24 AM.</small></i>

# In[1]:


import ROOT
from ROOT.VecOps import Take, Combinations


# RVec can be sorted in Python with the inbuilt sorting function because
# PyROOT implements a Python iterator

# In[2]:


v1 = ROOT.RVecD(3)
v1[0], v1[1], v1[2] = 1, 2, 3
v2 = ROOT.RVecD(2)
v2[0], v2[1] = -4, -5


# To get the indices, which result in all combinations, you can call the
# following helper.
# Note that you can also pass the size of the vectors directly.

# In[3]:


idx = Combinations(v1, v2)


# Next, the respective elements can be taken via the computed indices.

# In[4]:


c1 = Take(v1, idx[0])
c2 = Take(v2, idx[1])


# Finally, you can perform any set of operations conveniently.

# In[5]:


v3 = c1 * c2

print("Combinations of {} and {}:".format(v1, v2))
for i in range(len(v3)):
    print("{} * {} = {}".format(c1[i], c2[i], v3[i]))
print


# However, if you want to compute operations on unique combinations of a
# single RVec, you can perform this as follows.

# Get the indices of unique triples for the given vector.

# In[6]:


v4 = ROOT.RVecD(4)
v4[0], v4[1], v4[2], v4[3] = 1, 2, 3, 4
idx2 = Combinations(v4, 3)


# Take the elements and compute any operation on the returned collections.

# In[7]:


c3 = Take(v4, idx2[0])
c4 = Take(v4, idx2[1])
c5 = Take(v4, idx2[2])

v5 = c3 * c4 * c5

print("Unique triples of {}:".format(v4))
for i in range(len(v5)):
    print("{} * {} * {} = {}".format(c3[i], c4[i], c5[i], v5[i]))