The Ring programming language version 1.7 book - Part 30 of 196

Ring Documentation, Release 1.7
34.7 IsMacOSX() Function
We can check if the operating system is macOS or not using the IsMacOSX() function
Syntax:
IsMacOSX() ---> Returns 1 if the operating system is Mac OS X, Returns 0 if it's not
34.8 IsLinux() Function
We can check if the operating system is Linux or not using the IsLinux() function
Syntax:
IsLinux() ---> Returns 1 if the operating system is Linux, Returns 0 if it's not
34.9 IsFreeBSD() Function
We can check if the operating system is FreeBSD or not using the IsFreeBSD() function
Syntax:
IsFreeBSD() ---> Returns 1 if the operating system is FreeBSD, Returns 0 if it's not
34.10 IsAndroid() Function
We can check if the operating system is Android or not using the IsAndroid() function
Syntax:
IsAndroid() ---> Returns 1 if the operating system is Android, Returns 0 if it's not
34.11 Example
see "IsMSDOS() --> " + ismsdos() + nl
see "IsWindows() --> " + iswindows() + nl
see "IsWindows64() --> " + iswindows64() + nl
see "IsUnix() --> " + isunix() + nl
see "IsMacOSX() --> " + ismacosx() + nl
see "IsLinux() --> " + islinux() + nl
see "IsFreeBSD() --> " + isfreebsd() + nl
see "IsAndroid() --> " + isandroid() + nl
Output:
IsMSDOS() --> 0
IsWindows() --> 1
IsWindows64() --> 0
IsUnix() --> 0
IsMacOSX() --> 0
34.7. IsMacOSX() Function 262

IsLinux() --> 0
IsFreeBSD() --> 0
IsAndroid() --> 0
34.12 Windowsnl() Function
We can get the windows new line string using the Windowsnl() function.
Syntax:
WindowsNL() ---> Returns a string contains CR+LF = CHAR(13) + CHAR(10)
Example:
cStr = read("input.txt")
if iswindows()
cStr = substr(cStr,windowsnl(),nl)
ok
aList = str2list(cStr)
# to do - list items processing using "for in"
cStr = list2str(aList)
if iswindows()
cStr = substr(cStr,nl,windowsnl())
ok
write("ouput.txt",cStr)
34.13 Get Command Line Arguments
We can get the command line arguments passed to the ring script using the sysargv variable.
The sysargv variable is a list contains the command line parameters.
Example
see copy("=",30) + nl
see "Command Line Parameters" + nl
see "Size : " + len(sysargv) + nl
see sysargv
see copy("=",30) + nl
if len(sysargv) < 4 return ok
nStart = sysargv[3]
nEnd = sysargv[4]
for x = nStart to nEnd
see x + nl
next
Output
b:mahmoudappsring>ring testssyspara.ring 1 10
==============================
Command Line Parameters
34.12. Windowsnl() Function 263

Size : 4
ring
testssyspara.ring
1
10
==============================
1
2
3
4
5
6
7
8
9
10
34.14 Get Active Source File Name
We can get the active source file name (*.ring) using the filename() function
Syntax:
filename() ---> String contains the active source file name.
Example:
see "Active Source File Name : " + filename() + nl
Output:
Active Source File Name : testsfilename.ring
Example:
if sysargv[2] = filename()
see "I'm the main program file!" + nl
# we can run tests here!
else
see "I'm a sub file in a program" + nl
ok
34.15 PrevFileName() Function
Using the PrevFileName() function we can get the previous active source file name.
The previous file would be the file of the caller function, Or the file of the function that we called before calling
PrevFileName().
Syntax:
prevfilename() ---> String contains the previous source file name.
Example:
The next function in stdlib.ring uses the PrevFileName() to know if the file of the caller function is the main source
file of the program or not.
34.14. Get Active Source File Name 264

Func IsMainSourceFile
if PrevFileName() = sysargv[2]
return true
ok
return false
34.16 CurrentDir() Function
Return the path of the current directory
Syntax:
CurrenDir() ---> String contains the path of the currect directory
34.17 ExeFileName() Function
Return the Ring executable ﬁle name
Syntax:
exefilename() ---> String contains the Ring executable file name
34.18 ChDir() Function
Change the current directory
Syntax:
ChDir(cNewPath)
34.19 ExeFolder() Function
Return the Ring executable ﬁle path
Syntax:
exefolder() ---> String contains the Ring executable path
34.20 Version() Function
Return the Ring version
Syntax:
version() ---> String contains the Ring version
Output:
34.16. CurrentDir() Function 265

1.7
34.21 Shutdown() Function
Close the application
Syntax:
shutdown(nStatus) ---> Close the application
34.21. Shutdown() Function 266

CHAPTER
THIRTYFIVE
EVAL() AND DEBUGGING
In this chapter we are going to learn about
• Error Handling using Try/Catch/Done
• Eval() function
• Raise() function
• Assert() function
35.1 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 !
35.2 Eval() Function
We can execute code during the runtime from string using the Eval() function
Syntax:
267

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
35.3 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
35.3. Raise() Function 268

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
35.4 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
35.4. Assert() Function 269

CHAPTER
THIRTYSIX
DEMO PROGRAMS
In this chapter we will see simple demo programs
• Language Shell
• Main Menu
36.1 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
270

36.2 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
36.2. Main Menu 271

The Ring programming language version 1.7 book - Part 30 of 196

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The Ring programming language version 1.7 book - Part 30 of 196