calul.c:13: warning: incompatible implicit declaration of built-in function strlen
calul.c:13: warning: passing argument 1 of strlen makes pointer from integer without a cast
calul.c:16: warning: passing argument 1 of strlen makes pointer from integer without a cast
calul.c:19: warning: passing argument 1 of strlen makes pointer from integer without a cast
calul.c:22: error: invalid lvalue in unary &
calul.c:22: error: expected ) before r
calul.c:60: error: expected ; before } token
calul.c:60: error: expected declaration or statement at end of input