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| Topic complex |
Language elements |
| Function |
PROCEDURE |
Short |
Introduces a procedure |
| Syntax |
PROCEDURE Bezeichner[(Parameterliste)][: Grundtyp]; |
| Parameter |
parameter_list::=parameter{;parameter}.
parameter:=[VAR ]identifier_list : type.
identifier_list::=identifier{, identifier}.
type::=basic_type [Arraydef].
basic_type::=CHAR|BYTE|INTEGER|REAL|STRING|MARKS|TBITS.
Arraydef:=[dimension_list].
dimension_list::=number{,number}. |
| Return |
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| See also: |
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| Description |
Every executable module must include the procedure with name "Main".
Is a result type defined at declaring a procedur, it is a function-procedure which can be used in expressions.
A procedur has always the following structure:
PROCEDURE
ENDPROC
The procedure head is composed of a coercible procedure name, an optional paramter list and an optional result type.
The calling of a procedure is takes place by defining its name in expressions. Because a procedure is already known in its own body direct recursion is possible.
Example for a simple procedure:
PROCEDURE write_cgi_header;
cgiwriteln('content-type: text/html');
cgiwriteln('')
ENDPROCparameter list
You can commit values resp. variable references to the procedure. Those are defined directly after the procedur name in parenthesis. This is a formal parameter list:
PROCEDURE bold(line : STRING);
cgiwrite('');
cgiwritehtml(line);
cgiwriteln('')
ENDPROCCalling the procedure might look like:
fett('Headline');
fett(lower(cgigetparam('headline')));
With calling any expression of the (in the parameter list) defined type is in place of the formal parameters. At first this value is calculated and then is transmitted to the local variable of the procedure (here "line"). Such parameters are called value parameters (call by value).
Important: With calling a argument has to be at every place of the procedure list!
Besides the value parameters EASY also knows reference parameters. Here the formal parameter is considered as a free variable parameter. With calling this free variable parameter is replaced by the committed variable: Thus an assignment inside the procedure to the formal variable changes the committed variable. With calling a variable has to committed (and not an expression or a constant) instead of a reference parameter. Reference parameters are marked by a prefixed "VAR".
Example:
PROCEDURE douple(VAR x : REAL);
x:=2*x
ENDPROC The calling might look like:
VAR a : REAL;
a:=10;
douple(a); // now a has the value 20
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Example 1: High
PROCEDURE FieldTest(VAR a : INTEGER[,]);
VAR max_i : INTEGER = High(1,a);
VAR max_j : INTEGER = High(2,a);
...
ENDPROC
VAR x : INTEGER[10,5000];
VAR y : INTEGER[5,0];
...
FieldTest(x) // max_i=10; max_j=5000
FieldTest(y) // max_i=5; max_j=0
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