Another point is that a lingua franca is a common tongue for communication between people with different mother-tongues: not a replacement for native languages. For example in East & Central Africa Swahili is used for cross-communication, but individual ethnic groups maintain their cultural identities by holding onto their own languages. In this sense, I don't think you could easily find a developer who would struggle to understand anything (simple enough) written in Python, even though they don't use it on a day-to-day basis, so I think languages like Ruby/Python are already sufficient lingua francas for today's developers.
One more thing, maths notation is ridiculously diverse and overloaded and is in no way entirely uniform -- or even close. This is a problem when the disparity exists within a branch of maths, but an advantage when it's between very different areas, such as Analysis and Combinatorics.
One more thing, maths notation is ridiculously diverse and overloaded and is in no way entirely uniform -- or even close. This is a problem when the disparity exists within a branch of maths, but an advantage when it's between very different areas, such as Analysis and Combinatorics.