[adgjlsfhk1]

it's not. it uses type inference to infer types and llvm to compile down to native code. differentialequations.jl is often faster than the fastest C and Fortran solvers, and Octavian.jl often beats MKL at matrix multiplication.

[programmer_dude]

Type inference changes things. It's awesome that it can beat handwritten C and Fortran code.