Add support for basic arithmetic operators to git version

[chros73]

I. Summary
Add support for basic arithmetic operators (+, -, *, /, %) and min, max, count, avg, median functions.
All commands:

• support multiple arguments
• support list type as well
• restricted to integer arithmetic (as in bash), even /
  • rtorrent (and libtorrent) currently handles only integer variables
  • /, avg, median always round down

II. New commands in rtorrent

• math.add
• math.sub
• math.mul
• math.div
• math.mod
• math.min
• math.max
• math.cnt
• math.avg
• math.med

III. Arithmetic operators in action

# Subtract 3 numbers: -4
print=(math.sub,5,2,7)
# Divide 3 numbers: 2 !
print=(math.div,80,9,4)

# Calculate size of a download using its size of files (example using list type)
print=(math.add,(f.multicall,,f.size_bytes=))

# Get average size in Bytes of downloads in main view
print=(math.div,(math.add,(d.multicall2,main,d.size_bytes=)),(view.size,main))

math.min and math.max can be used as variable assignment based on intervals as well:

# Assign 0 if value smaller than 0, or assign value otherwise ( x >= 0 ? x : 0 )
print=(math.max,0,(math.sub,2,7))
# Assign 0 if value smaller than 0, 100 if value is bigger than 100, or assign value otherwise ( x < 0 ? 0 : (x > 100 ? 100 : x) )
print=(math.max,0,(math.min,100,(math.div,500,2)))

[chros73]

Rename commands as @rakshasa suggested:

• math.add
• math.sub
• math.mul
• math.div
• math.mod
• math.min
• math.max

Note: Original post has been edited.

[chros73]

Add 2 new commands:

• math.cnt (count)
• math.avg

Note: Original post has been edited.

[chros73]

Add 1 new command for median:

• math.med

Note: Original post has been edited.