Bash let function

[Gianluca Graziadei S308963]

Dear all,
for academic use I need to obtain the code of let.c (builtin function).
The main idea is to improve (if possible) the let shell func to accept 
also the floating point type and develop the support for sin(), cos(), 
sqrt() and other Math.h's functions.

I have downloaded the stable bash release but I have found let.def file 
(no let.c), can you help me ?

Thanks for your attention and support.

Best regards,
Gianluca Graziadei
Graduate student @ Politecnico di Torino