scanf interactive program

rocketman03 · 11-14-2008, 08:30 PM

hey..is there a way to execute scanf before all values have been entered. i am trying to create a program so that when the user types in a 1 2.. it takes him to the 1 , 2 element of a 2d array.
but there is also a function r 1 2 3 4 which takes four parameters n draws an ascii rectangle. so how do i make it so that scanf is able to distinguish between 2 and 4 inputs and knows which function to call;

Code:

scanf("%c %d %d %d %d",&ask,&one,&two,&three,&four);

first one is either a or r and the rest are parameters..i need to make it so that the user can type in a command at any time and the correct function will be called.
theres also d and q.

so the available options are :
a 1 2
r 1 2 3 4
d
q

is it possible with scanf ? or should i use something else
however , i am not allowed to use command line arguments.

tabstop · 11-14-2008, 08:47 PM

scanf returns the number of input variables assigned to.

However! There's no need to get all fancy (unless you want to), for scanf will leave unused input in the input buffer. So you can read one character, and then based on that character, read 0, 2 or 4 more numbers during the processing later on, and they will still be there.

rocketman03 · 11-14-2008, 08:56 PM

Code:

void menu()
{
	int c;
	while(ask != 'q'){
	rewind(stdin);
	printf("p: point , r: rectangle , d: draw , q: quit\n");
	if(c=scanf("%c%d%d%d%d",&ask,&one,&two,&three,&four) < 2)
	{ d(); }
	if ( c < 4)
	{ p(one , two); }
	if (c < 6)
	{ r(one , two , three , four); }
}
}

i did this but even if i press enter it doesnt do anything untill i give it 4 inputs!

tabstop · 11-14-2008, 08:58 PM

That's true. I was forgetting that since whitespace is ignored by scanf, more or less, that enter would also be ignored.

So, just do it the way I recommended.

rocketman03 · 11-14-2008, 09:19 PM

how do i do that ?
i tried this but still have the same problem ?

Code:

void menu()
{
	while(ask != 'q'){
	rewind(stdin);
	printf("p: point , r: rectangle , d: draw , q: quit\n");
	scanf("%c%d%d%d%d",&ask,&one,&two,&three,&four);
	if(ask == 'p')
	p(one , two);
	else if (ask == 'r')
	r(one , two , three , four);
	else if(ask == 'd')
	d();
	else
	q();
	}
}

tabstop · 11-14-2008, 09:34 PM

Quote:

%c%d%d%d%d"

Looks like five things to me. Read in one thing, and one thing only. Then, only if circumstances warrant, do you read in the other four (or two).

rocketman03 · 11-14-2008, 09:40 PM

Oh ! now i know what you mean..but the thing is were supposed to press enter only once and its supposed to figure out which function to call..if i read only one thing then i will have to press multiple enters right ?

tabstop · 11-14-2008, 09:44 PM

Quote:

Originally Posted by rocketman03

Oh ! now i know what you mean..but the thing is were supposed to press enter only once and its supposed to figure out which function to call..if i read only one thing then i will have to press multiple enters right ?

Of course not.

rocketman03 · 11-14-2008, 09:52 PM

wow! i didnt know that!..ok..im really close

Code:

void menu()
{
	while(ask != 'q'){
	rewind(stdin);
	printf("p: point , r: rectangle , d: draw , q: quit\n");
	scanf("%c",&ask);
	if(ask == 'p'){
	scanf("%d,%d",&one , &two);
	p(one , two);}
	else if (ask == 'r')
	{
	scanf("%d,%d,%d,%d",&one , &two , &three , &four);
	r(one , two , three , four);
	}
	else if(ask == 'd')
	d();
	else
	q();
	}
}

i have this but if i do this it gives me just the blank board without any points or values..and if i remove the rewind(stdin) it gives me 4 outputs but even those are wrong.. what am i doing wrong ?

rocketman03 · 11-14-2008, 09:54 PM

oh my god! nevermind , i put commas in the scanf !..my fault!..thank you sooo much! it worked!!

Thank you !!

11-14-2008, 08:30 PM	#1
rocketman03 Registered User Join Date: Oct 2008 Posts: 72	scanf interactive program hey..is there a way to execute scanf before all values have been entered. i am trying to create a program so that when the user types in a 1 2.. it takes him to the 1 , 2 element of a 2d array. but there is also a function r 1 2 3 4 which takes four parameters n draws an ascii rectangle. so how do i make it so that scanf is able to distinguish between 2 and 4 inputs and knows which function to call; Code: scanf("%c %d %d %d %d",&ask,&one,&two,&three,&four); first one is either a or r and the rest are parameters..i need to make it so that the user can type in a command at any time and the correct function will be called. theres also d and q. so the available options are : a 1 2 r 1 2 3 4 d q is it possible with scanf ? or should i use something else however , i am not allowed to use command line arguments.
rocketman03 is offline

11-14-2008, 08:47 PM	#2
tabstop and the Hat of Guessing Join Date: Nov 2007 Posts: 8,740	scanf returns the number of input variables assigned to. However! There's no need to get all fancy (unless you want to), for scanf will leave unused input in the input buffer. So you can read one character, and then based on that character, read 0, 2 or 4 more numbers during the processing later on, and they will still be there.
tabstop is offline

11-14-2008, 08:58 PM	#4
tabstop and the Hat of Guessing Join Date: Nov 2007 Posts: 8,740	That's true. I was forgetting that since whitespace is ignored by scanf, more or less, that enter would also be ignored. So, just do it the way I recommended.
tabstop is offline

11-14-2008, 09:40 PM	#7
rocketman03 Registered User Join Date: Oct 2008 Posts: 72	Oh ! now i know what you mean..but the thing is were supposed to press enter only once and its supposed to figure out which function to call..if i read only one thing then i will have to press multiple enters right ?
rocketman03 is offline

11-14-2008, 09:52 PM	#9
rocketman03 Registered User Join Date: Oct 2008 Posts: 72	wow! i didnt know that!..ok..im really close Code: void menu() { while(ask != 'q'){ rewind(stdin); printf("p: point , r: rectangle , d: draw , q: quit\n"); scanf("%c",&ask); if(ask == 'p'){ scanf("%d,%d",&one , &two); p(one , two);} else if (ask == 'r') { scanf("%d,%d,%d,%d",&one , &two , &three , &four); r(one , two , three , four); } else if(ask == 'd') d(); else q(); } } i have this but if i do this it gives me just the blank board without any points or values..and if i remove the rewind(stdin) it gives me 4 outputs but even those are wrong.. what am i doing wrong ?
rocketman03 is offline

11-14-2008, 09:54 PM	#10
rocketman03 Registered User Join Date: Oct 2008 Posts: 72	oh my god! nevermind , i put commas in the scanf !..my fault!..thank you sooo much! it worked!! Thank you !!
rocketman03 is offline

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