eval lambda expression
sum-of-square test case
builtin_sub
builtin_div
builtin_eq
builtin_gt
builtin_le and builtin_ge
builtin_and
builtin_or
builtin_not
eval cond
modify builtin_sub to support neg op, i.e., (- x)
abs() testcase
builtin_and() and builtin_or() support multi operands
move repl() to repl.h
do_repl()
expr()
repl : multi line list support