Add check bison version in configure.ac file.
To build correctly matiec we need bison greater or equals than 2.4 version.
Now the "configure" script is able to check if system has correctly requirements.
FUNCTION_BLOCK INTEGRAL
VAR_INPUT
RUN : BOOL ; (* 1 = integrate, 0 = hold *)
R1 : BOOL ; (* Overriding reset *)
XIN : REAL ; (* Input variable *)
X0 : REAL ; (* Initial value *)
CYCLE : TIME ; (* Sampling period *)
END_VAR
VAR_OUTPUT
Q : BOOL ; (* NOT R1 *)
XOUT : REAL ; (* Integrated output *)
END_VAR
Q := NOT R1 ;
IF R1 THEN XOUT := X0 ;
ELSIF RUN THEN XOUT := XOUT + XIN * TIME_TO_REAL(CYCLE);
END_IF ;
END_FUNCTION_BLOCK