Adding switches to function

[CatFace]

Hey again...

This time I want to make the function paramaters operate a switch from a function variable, how is this done?

eg

int 123(string 456)
{
switch(456)
case 'command1': cout << timeStr << ": command1"; break;
case 'command2': cout << timeStr << ": command2"; break;
default: cout << "invalid input."; break;
}

The output need to be like this...

I have a variable called timeStr which needs to be before the function paramater.

[variable]: "whatever was in the function paramater".



Thanks

[GCDEF]

switch only works with numeric expressions.

[CatFace]

oh ok thanks, is there a way to use the string and compare it to a variable?

so it compares the "456" string and if it is command1 then number 1. If it is command2 then it would interpret it as number 2.

int 123(string 456)
{

if 456 = ("command1")
operatorForSwitch = 1;
if 456 = ("command2")
operatorForSwitch = 2;

switch(456)
case 'command1': cout << timeStr << ": command1"; break;
case 'command2': cout << timeStr << ": command2"; break;
default: cout << "invalid input."; break;
}

[GCDEF]

Giving your string variable a numeric name is confusing. Why don't you use real compilable syntax to show what you're trying to do, or at least unambiguous pseudocode.

You could use the if statements to come up with a numeric value for your switch, but what's the point? As long as you're evaluating the value in your string with if, you may as well use those statements to execute the appropriate code.

[CatFace]

Okay, I was only using switchs becuase that's what I learnt instead of multiple if statements

Thanks.

[D_Drmmr]

Variable, function and class names in C++ must start with a letter.
There are really a lot of basic syntax errors in your code. You should study a beginners' C++ book. See the FAQ for recommendations.

[CatFace]

oh, The 123 and 456 where just like xyz, not actual filenames but examples :P

[ninja9578]

You want something like this

//This macro is easier to understand than negating a compare function
#define AreSame(p1, p2)\
    !p1.compare(p2)

if (AreSame(xyz, "SomeValue")){
   do something
} else if (AreSame(xyz, "Some Other Value")){
   do something else
}...

[GCDEF]

You want something like this

//This macro is easier to understand than negating a compare function
#define AreSame(p1, p2)\
    !p1.compare(p2)

if (AreSame(xyz, "SomeValue")){
   do something
} else if (AreSame(xyz, "Some Other Value")){
   do something else
}...

What's wrong with just using == to compare the string to the literal?

[CatFace]

ok.
Is AreSame a real function and what does this do?

!p1.compare(p2)?

[laserlight]

Is AreSame a real function and what does this do?

No, it is a macro. It basically replaces AreSame(x, y) for some expressions x, y with !x.compare(y).

!p1.compare(p2)?

That is effectively the same as p1.compare(p2) == 0, but the latter expresses the idea that this is a test of equality better, thus addressing ninja9578's objection. However, even better yet would be: p1 == p2, e.g., xyz == "SomeValue".

[servalsoft]

Have a look at this, it uses strcmp the syntax is

int strcmp ( const char * str1, const char * str2 );

so u can have something like

#include stdio.h
#include string.h
...
...

if (strcmp(string1, string2) = = 0) //both sting are equal
         do something;
else if (strcmp(string1, string3)  < 0) //1st string < than second
          do something else;
else do another thing;

strcmp in my opinion is better to use for comparing strings, or array of char.

If you must use a switch, I believe you can only switch int or a char. ie 1, 2, 40, 'a' , ' n', 'M'....

[laserlight]

strcmp in my opinion is better to use for comparing strings, or array of char.

strcmp() would be appropriate for comparing null terminated strings, but I hope and believe that CatFace is using std::string objects.

[Ajay Vijay]

If the string is treated as command (as in shell), you can write a function which takes string (the command), and return numeric constant for the command. Like:

int GetCommandId(const string& cmd)
{
if(cmd=="list")
return 0;
if(cmd=="delete")
return 1;
if(cmd=="find")
return 2;
....
}

Then use the return value of 'GetCommandId' in switch:

switch(GetCommandId(str))
{
case 1:
...
}

You may also use #define or enum constants for better readability.