Correctly identify errors when parsing erroneous code (make sure flex goes back to INITIAL state when code contains errors that do not allow determining whether ST or IL is being parsed)
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# IL operators #
################
# which are not simultaneously
# - keywords (AND, OR, NOT, MOD, XOR),
# - or standard funtion name (which by implication are also keywords)
# (AND, OR, NOT, MOD, XOR, as well as, GE, GT, LE, LT, EQ, NE, SUB, ADD, MUL, DIV)
# - or standard function block name (which by implication are also keywords)
# - invalid identifier name (&, &N)
ANDN
CAL
CALC
CALCN
CD
CLK
CU
IN
JMP
JMPC
JMPCN
LD
LDN
ORN
PT
PV
R
R1
RET
RETC
RETCN
S
S1
ST
STN
XORN
##################
# SFC qualifiers #
##################
D
DS
L
N
P
#R -> also an IL operator
#S -> also an IL operator
SD
SL
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# Task initialisers #
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PRIORITY
SINGLE
INTERVAL