It is stated that 1--1 is valid and that an unary minus is not separated by a whitespace before parentheses. Your example follow these rules.

Hi everyone, I use haskell language.

In random tests, I get a random input string
"((((94.0))-54.98))-89.28-(88.66)+-59.25+75.61+4.88/(44.42)/(79.75)*-60.81*3.72/(19.72*10.46)-58.1/(7.55)*23.37+32.0/(97.63)-(79.92*(1.71-16.82))/(--(28.95)/((55.88/(67.58))))/(69.66)+95.05*(37.3*(5.1*44.66*39.81)-17.23)*80.85+(48.43/(86.06))*(-88.39)/((32.31-31.49*32.76))"
to calc, I get a substring --(28.95), Is that right? I am not found this rule in the description.

I will retry later.
Thanks.

The time restriction is from Codewars. I can nothing about that. Sorry but it is not an issue.
CW seems to be very slow, maybe you can retry later.

your haskell testing script is wrong.