is [C routine]
We can import a c function/routine into e and use it as regular e method. There are two ways to this.
Syntax
- Local Method :e-method-name(param,...)[:result-type] is C routine c-routine-name
- Global Method :routine e-routine-name(param, ...) [:result-type] [is C routine c-routine-name]
|
| ||||||||
| Example-Global routine | ||||||||
| Below is the c file which prints 'Hello World' |
1 #include
2
3 void hello() {
4 printf("Hello World\n");
5 }
| Below is e code which uses the above c function. |
| . |
1 <'
2 routine hello_world() is C routine hello;
3
4 extend sys {
5 run() is also {
6 hello_world();
7 };
8 };
9 '>
| Compiling the example | ||
| . | ||
| Operation | Commands | Â |
| Create c object file | gcc -c -o hello.o hello.c | Â |
| Link c to e | sn_compile.sh -l hello.o methods_ex2.e -o hello | Â |
| Simulate | hello -c "test" | Â |
| Example-Local routine | ||
| . | ||
1 <'
2 extend sys {
3 hello_world() is C routine hello;
4 run() is also {
5 hello_world();
6 };
7 };
8 '>
is also
"is also" is used for extending existing method/TCM. When we use "is also" it adds new lines of code/functionality after the existing code as shown in below example.
1 <'
2 struct hello {
3 say_hello() is {
4 out ("Hello World");
5 };
6 };
7 // Extend the orginal struct so
8 // That we can extend the method
9 extend hello {
10 say_hello() is also {
11 out("This is Deepak");
12 };
13 };
14
15 extend sys {
16 hello : hello;
17 run() is also {
18 hello.say_hello();
19 };
20 };
21 '>
is first
"is first" is used for extending existing method/TCM. When we use "is first" it adds new lines of code/functionality before existing code shown in below example.
1 <'
2 struct hello {
3 say_hello() is {
4 out ("Hello World");
5 };
6 };
7 // Extend the orginal struct so
8 // That we can extend the method
9 extend hello {
10 say_hello() is first {
11 out("I Want To Say");
12 };
13 };
14
15 extend sys {
16 hello : hello;
17 run() is also {
18 hello.say_hello();
19 };
20 };
21 '>
is only
"is only" is used for over riding existing method/TCM. When we use "is only" it over rides the existing code/functionality before existing code and replaces with new code as shown in below example. This basically over rides any previously used "is also" and "is first" extensions.
1 <'
2 struct hello {
3 say_hello() is {
4 out ("Hello World");
5 };
6 };
7 // Extend the orginal struct so
8 // That we can extend the method
9 extend hello {
10 say_hello() is only {
11 out("Hell With The World");
12 };
13 };
14
15 extend sys {
16 hello : hello;
17 run() is also {
18 hello.say_hello();
19 };
20 };
21 '>
is empty/undefines
Declares an abstract regular method or an abstract TCM with no defined functionality. Abstract methods are place holders that you can extend at a later point. A TCM is a time-consuming method that is distinguished from a regular method by the presence of @event and can use time-consuming actions such as sync and wait.
Note : Following restrictions apply for a abstract methods.
- The maximum number of parameters you can declare for a TCM is 14.
- You cannot define methods with variable argument lists.
undefined
No action block is defined for the method yet; an action block must be defined in a subsequent module before this method is called. Calling the method before it is defined is illegal.
1 <'
2 struct hello {
3 say_hello() is undefined ;
4 };
5 // Extend the orginal struct
6 // So that we can define functionality for method
7 extend hello {
8 say_hello() is {
9 out("Hello World");
10 };
11 };
12
13 extend sys {
14 hello : hello;
15 run() is also {
16 hello.say_hello();
17 };
18 };
19 '>
empty
The action block is empty; however, calling the method before it is defined is legal. Empty value-returning methods return the default value for the type.
1 <'
2 struct hello {
3 say_hello() is empty ;
4 };
5 // Extend the orginal struct
6 // So that we can define functionality for method
7 extend hello {
8 say_hello() is {
9 out("Hello World");
10 };
11 };
12
13 extend sys {
14 hello : hello;
15 run() is also {
16 hello.say_hello();
17 };
18 };
19 '>
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