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And expression is a mathematical, logical or relational formula that can be evaluated at run time. More formally :-
And expressions is a either a term, or term + term or term
- term or a logical expression or a relational expression.
A term is either :-
term * term term / term term DIV term term MOD term - term ( expression ) Numbers are standard C double precision numbers :-
1 -1 1e300 // Very big number -1.23e-300 // A Number very near zero
Logical expressions are either :-
A relational expression is either an adjacency expression or one of :-
An adjacency expression allows one to query the state of variables in neighbouring cells.
An adjacency expression is one of the following :-
A cellBasedId is a cell based specie name, or a local variable of a cell based specie or a cell based data stream. See See section References for details.
For example, if the beastie stick_bait started to grow in this cell if any
adjacent cell had stick bait growing, then one might express this as :-
if any adjacent stick_bait > 2 then stick_bait += 0.5; endif;
Range expressions allow
one to query data streams. It is not meaningful to sample a data stream at one point,
rather we need to know the state of the variable over a period of time. The langauge makes
available two special constructs to query data streams. For example :- If we wish to know
whether the concentration was in the range 25 to 40 for most of the time in the last time
step we can simple say :- concentration in [25, 40]. By most of the time we
by default mean 90% of the time, or whatever the current value of the variable
"most_times" is. ("most_times" is a predefined system variable that is
by default set to 0.9)
qualIdent in [lower, upper];
If the data stream qualIdent is greater than lower and less
than upper for most_times * step_size seconds in
the last time step, then the expression evaluates as true otherwise as false. (See section
The Boolean convention)
qualIdent in [lower, upper, most_times, period];
If the data stream qualIdent is greater than lower and less
than upper for most_times * period * step_size
seconds in the preceding period steps, then the expression evaluates as true
otherwise as false. (See section The Boolean convention)
rules : cells links io_statements setup_statements species THE_END ;
setup_statements : /* Nothing */ | statements;
cells : CELLS cellList ';' ;
cellList : IDENTIFIER |
cellList ',' IDENTIFIER ;
links : link | links link;
link : LINK IDENTIFIER ',' IDENTIFIER ';' ;
io_statements : input output | output input;
input : INPUT FROM STRING ';' ;
output : OUTPUT TO STRING ';' ;
species : specie |
species specie;
specie : specie_header specie_body end_specie ;
end_specie : END SPECIE ';' |
END SPECIE IDENTIFIER ';' ;
specie_header : /* Default is cell based. */ SPECIE IDENTIFIER ';' |
CELL BASED SPECIE IDENTIFIER ';' |
ECOSYSTEM WIDE SPECIE IDENTIFIER ';' ;
specie_body : declarations start_statements running_rules;
declarations : /* Nothing */ |
DECLARE decl_list ';' ;
decl_list : IDENTIFIER |
decl_list ',' IDENTIFIER ;
start_statements : statements RUNNING RULES ';' |
/* Nothing */ RUNNING RULES ';' ;
running_rules : statements ;
statements : statement | statements statement;
statement : /* Empty statement */ ';' |
assignment_statement |
if_then_endif |
trace_statement |
print_statement |
if_then_else_endif ;
trace_statement : TRACE expression ';'
print_statement : one_arg_print | two_arg_print | show_statement;
one_arg_print : PRINT expression ';'
two_arg_print : PRINT STRING expression ';'
show_statement : SHOW qualIdent ';'
if_then_endif : if_then statements ENDIF ';' ;
if_then : IF expression THEN ;
if_then_else_endif : if_then statements else statements ENDIF ';';
else : ELSE;
unqualifiedIdent : IDENTIFIER;
qualifiedIdent : IDENTIFIER '.' IDENTIFIER;
qualifiedAt : IDENTIFIER '.' IDENTIFIER '@' IDENTIFIER;
unqualifiedAt : IDENTIFIER '@' IDENTIFIER;
notAtted : unqualifiedIdent | qualifiedIdent ;
atted : unqualifiedAt | qualifiedAt ;
qualIdent : atted | notAtted;
assignment_statement : assignment | increment | decrement;
assignment : qualIdent BECOMES expression ';';
increment : qualIdent INCREMENT expression ';';
decrement : qualIdent DECREMENT expression ';';
expression : term |
expression '+' term |
expression '-' term |
logical_expression |
relational_expression ;
term : REAL |
range |
qualIdent |
term '*' term |
term '/' term |
term DIV term |
term MOD term |
'-' term %prec UMINUS |
'(' expression ')' ;
range : mono_stream_range | ecowide_range ;
mono_stream_range : two_arg_plain | four_arg_plain;
two_arg_plain : qualIdent IN two_arg_range;
four_arg_plain : qualIdent IN four_arg_range;
ecowide_range :
two_arg_any |
four_arg_any |
two_arg_all |
four_arg_all ;
two_arg_any : qualIdent IN ANY CELL two_arg_range;
two_arg_all : qualIdent IN ALL CELLS two_arg_range;
four_arg_any : qualIdent IN ANY CELL four_arg_range;
four_arg_all : qualIdent IN ALL CELLS four_arg_range;
two_arg_range : '[' expression ',' expression ']' ;
four_arg_range : '[' expression ',' expression ',' expression ',' expression ']';
logical_expression : expression AND expression |
expression OR expression |
NOT term |
expression XOR expression ;
relational_expression : adjacency_expression | rel_exp;
rel_exp : expression '>' expression |
expression '<' expression |
expression '=' expression |
expression NE expression |
expression LE expression |
expression GE expression ;
cellBasedId : notAtted;
adjacency_expression :
ALL ADJACENT cellBasedId '>' expression |
ALL ADJACENT cellBasedId '<' expression |
ALL ADJACENT cellBasedId '=' expression |
ALL ADJACENT cellBasedId NE expression |
ALL ADJACENT cellBasedId GE expression |
ALL ADJACENT cellBasedId LE expression |
ANY ADJACENT cellBasedId '>' expression |
ANY ADJACENT cellBasedId '<' expression |
ANY ADJACENT cellBasedId '=' expression |
ANY ADJACENT cellBasedId NE expression |
ANY ADJACENT cellBasedId GE expression |
ANY ADJACENT cellBasedId LE expression ;
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