The Ring programming language version 1.6 book - Part 29 of 189

1. Ring Documentation, Release 1.6
1.6
33.21 Shutdown() Function
Close the application
Syntax:
shutdown(nStatus) ---> Close the application
33.21. Shutdown() Function 253

2. CHAPTER
THIRTYFOUR
EVAL() AND DEBUGGING
In this chapter we are going to learn about
• Error Handling using Try/Catch/Done
• Eval() function
• Raise() function
• Assert() function
34.1 Try/Catch/Done
Syntax:
Try
Statements...
Catch
Statements...
Done
The statements in the Try block will be executed, if any error happens then the statements in the catch block will be
executed.
Inside the catch block we can use the variable cCatchError to get the error message
Example:
Try
see 5/0
Catch
see "Catch!" + nl + cCatchError
Done
Output:
Catch!
Error (R1) : Cann't divide by zero !
34.2 Eval() Function
We can execute code during the runtime from string using the Eval() function
Syntax:
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3. Ring Documentation, Release 1.6
Eval(cCode)
Example:
Eval("nOutput = 5+2*5 " )
See "5+2*5 = " + nOutput + nl
Eval("for x = 1 to 10 see x + nl next")
Eval("func test see 'message from test!' ")
test()
Output:
5+2*5 = 15
1
2
3
4
5
6
7
8
9
10
message from test!
We can use the Return command to return a value
Example:
see Eval("return 5*5")
Output:
25
34.3 Raise() Function
We can raise an exception using the Raise() function
Syntax:
Raise(cErrorMessage)
The function will display the error message then end the execution of the program.
We can use Try/Catch/Done to avoid exceptions generated by raise() function.
Example:
nMode = 10
if nMode < 0 or nMode > 5
raise("Error : nMode not in the range 1:4")
ok
Output:
Line 4 Error : nMode not in the range 1:4
In raise in file testsraise.ring
34.3. Raise() Function 255

4. Ring Documentation, Release 1.6
Example:
try
testmode(6)
catch
see "avoid raise!"
done
testmode(-1)
func testmode nMode
if nMode < 0 or nMode > 5
raise("Error : nMode not in the range 1:4")
ok
Output:
avoid raise!
Line 12 Error : nMode not in the range 1:4
In raise In function testmode() in file testsraise2.ring
called from line 7 in file testsraise2.ring
34.4 Assert() Function
We can use the Assert() function to test conditions before executing the code
If the test fail the program will be terminated with an error message contains the assert condition.
Syntax:
Assert( condition )
Example:
x = 10
assert( x = 10)
assert( x = 100 )
Output:
Line 3 Assertion Failed!
In assert in file testsassert.ring
34.4. Assert() Function 256

5. CHAPTER
THIRTYFIVE
DEMO PROGRAMS
In this chapter we will see simple demo programs
• Language Shell
• Main Menu
35.1 Language Shell
We can create simple interactive programming environment using the next program
while true
see nl + "code:> "
give cCode
try
eval(cCode)
catch
see cCatchError
done
end
Output:
code:> see "hello world"
hello world
code:> for x = 1 to 10 see x + nl next
1
2
3
4
5
6
7
8
9
10
code:> func test see "Hello from test" + nl
code:> test()
Hello from test
code:> bye
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6. Ring Documentation, Release 1.6
35.2 Main Menu
Example:
# Demo Program
while true
see "
Main Menu
===========
[1] Say Hello
[2] Sum two numbers
[3] Stars
[4] Fact
[5] Exit
" give nMenu see nl
# we can use Switch-ON-Other-OFF instead of IF-BUT-ELSE-OK
Switch nMenu
On 1 sayhello()
On 2 Sum()
On 3 Stars()
On 4
see "Enter Number : " give x
see "Output : "
Try
see Fact(number(x))
Catch
see "Error in parameters!" + nl
Done
On "5" return
Other see "bad option" + nl
Off
end
func sayhello
see "Enter your name ? " give fname
see "Hello " + fname + nl
func sum
see "number 1 : " give num1 see "number 2 : " give num2
see "Sum : " see 0 + num1 + num2
func stars
for x = 1 to 10
see space(8)
for y = 1 to x see "*" next see nl
next
func fact x if x = 0 return 1 else return x * fact(x-1) ok
35.2. Main Menu 258

7. Ring Documentation, Release 1.6
func space x y = "" for t=1 to x y += " " next return y
Output:
Main Menu
===========
[1] Say Hello
[2] Sum two numbers
[3] Stars
[4] Fact
[5] Exit
1
Enter your name ? Mahmoud Fayed
Hello Mahmoud Fayed
Main Menu
===========
[1] Say Hello
[2] Sum two numbers
[3] Stars
[4] Fact
[5] Exit
2
number 1 : 3
number 2 : 4
Sum : 7
Main Menu
===========
[1] Say Hello
[2] Sum two numbers
[3] Stars
[4] Fact
[5] Exit
3
*
**
***
****
*****
******
*******
********
*********
**********
Main Menu
===========
[1] Say Hello
[2] Sum two numbers
35.2. Main Menu 259

8. Ring Documentation, Release 1.6
[3] Stars
[4] Fact
[5] Exit
4
Enter Number : 5
Output : 120
Main Menu
===========
[1] Say Hello
[2] Sum two numbers
[3] Stars
[4] Fact
[5] Exit
5
35.2. Main Menu 260

9. CHAPTER
THIRTYSIX
ODBC FUNCTIONS
This chapter contains the ODBC functions provided by the Ring programming language.
• odbc_init()
• odbc_drivers()
• odbc_datasources()
• odbc_close()
• odbc_connect()
• odbc_disconnect()
• odbc_execute()
• odbc_colcount()
• odbc_fetch()
• odbc_getdata()
• odbc_tables()
• odbc_columns()
• odbc_autocommit()
• odbc_commit()
• odbc_rollback()
Before using the next function load the odbclib.ring library
load "odbclib.ring"
# Use ODBC functions
36.1 odbc_init() Function
We can create ODBC Handle using the odbc_init() function
Syntax:
odbc_init() ---> ODBC Handle
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10. Ring Documentation, Release 1.6
36.2 odbc_drivers() Function
We can get a list of ODBC drivers using the odbc_drivers() function
Syntax:
odbc_drivers(ODBC Handle) ---> List of Drivers
36.3 odbc_datasources() Function
We can get a list of ODBC data sources using the odbc_datasources() function
Syntax:
odbc_datasources(ODBC Handle) ---> List of Data sources
36.4 odbc_close() Function
After the end of using ODBC functions we can free resources using ODBC_Close() function
Syntax:
odbc_close(ODBC Handle)
36.5 Print List of ODBC Drivers
The next example print a list of ODBC drivers.
See "ODBC test 1" + nl
oODBC = odbc_init()
See "Drivers " + nl
see odbc_drivers(oODBC)
odbc_close(oODBC)
Output:
ODBC test 1
Drivers
Microsoft Access-Treiber (*.mdb) - SQLLevel=0
Driver do Microsoft Paradox (*.db ) - SQLLevel=0
Driver do Microsoft Excel(*.xls) - SQLLevel=0
Microsoft Text Driver (*.txt; *.csv) - SQLLevel=0
Driver da Microsoft para arquivos texto (*.txt; *.csv) - SQLLevel=0
Microsoft dBase-Treiber (*.dbf) - SQLLevel=0
SQL Server - CPTimeout=60
Microsoft Excel Driver (*.xls) - SQLLevel=0
Driver do Microsoft dBase (*.dbf) - SQLLevel=0
Microsoft Paradox-Treiber (*.db ) - SQLLevel=0
Microsoft ODBC for Oracle - CPTimeout=120
Microsoft Text-Treiber (*.txt; *.csv) - SQLLevel=0
Microsoft Excel-Treiber (*.xls) - SQLLevel=0
Microsoft Access Driver (*.mdb) - SQLLevel=0
Driver do Microsoft Access (*.mdb) - SQLLevel=0
36.2. odbc_drivers() Function 262