Problem with locate command

[Phenominalprogrammer]

When I try code like this I get

Illegal function call

Code: QB64: [Select]

1. Location_x = 100
2. Location_y = 25
3.  
4. Locate location_x, location_y
5.  
6. Print "a nice test"
7.  

[bplus]

You can only LOCATE within the character cells of the screen. One character is 8 X 16 pixels.
Default screen is 640 X 400? 640 /8 = 80 max cell column

400 / 16 = 25 rows

PLUS if you start to print past the last row or 2 the screen starts scrolling or will switch to _FONT 8 first.

Welcome to the forum @Phenominalprogrammer

[SMcNeill]

You can only LOCATE within the character cells of the screen.

One point of quirkiness which you may not be aware of, Bplus: That statement isn't correct in 100% of all cases. 

LOCATE with a variable-width font, and there's no set character cells to reference.  Instead, you LOCATE X-pixels width, Y-rows down.   (It's not row/column, and it's not  pixel/pixel reference; it's a hybrid pixel/row reference.)

Of course, SCREEN 0 (which is all that's referenced by default in the original code) won't even work with variable-width fonts at all, so for most folks it's a moot distinction.  ;)

[TempodiBasic]

WHILE  Bplus AND SMcNeill give the right tecnical informations
 I must add this one
  your code posted is a QBasic/QB way to use screen mode in console state or in other words
your code

Code: QB64: [Select]

1. Location_x = 100
2. Location_y = 25
3.  
4. LOCATE location_x, location_y
5.  
6. PRINT "a nice test"
7.  

is equal to

Code: QB64: [Select]

1. SCREEN 0
2. Location_x = 100
3. Location_y = 25
4.  
5. LOCATE location_x, location_y
6.  
7. PRINT "a nice test"
8.  

because in QBasic/QB if you don't specify the screen mode that , for default, it  is the console screen only text 80x25, 31 foreground colors and 7 background colors (32 and 8 if you include the black). QB64 emulates QB so you get the same error!
But this syntax must be deprecated if we must give more importance to QB64 than Qbasic/QB, in fact in QB64
you should write so

Code: QB64: [Select]

1. SCREEN _NEWIMAGE (80,25,0)
2. Location_x = 100
3. Location_y = 25
4.  
5. LOCATE location_x, location_y
6.  
7. PRINT "a nice test"
8.  

and in this case it is obvious why you get the error!

WEND

[bplus]

Code: QB64: [Select]

1. _TITLE "Locate Test in default screen, press spacebar for another 20, press esc to quit"
2. T$ = "A nice test."
3. lt = LEN(T$)
4. DO
5.     CLS
6.     FOR i = 1 TO 20
7.  
8.         ' KEEPING Row and Col in bounds for LOCATE
9.         row = INT(RND * 25) + 1: col = INT(RND * (80 - lt)) + 1
10.         'LOCATE 1, 1: PRINT SPACE$(20) 'debug row and col
11.         'LOCATE 1, 1: PRINT row, col
12.  
13.         LOCATE row, col: PRINT T$;
14.     NEXT
15.     SLEEP
16. LOOP UNTIL _KEYDOWN(27)
17.  
18.  
19.  

[MWheatley]

I'd add that LOCATE has for me always been a difficult command in terms of code compatibility: different BASICs implement it in different ways.  I once ported some regularly-used statistics calculations over to Liberty BASIC, in the days before QB64 (or at least, before I discovered QB64).

Liberty BASIC implements LOCATE the other way round -- ie, not LOCATE x, y but instead LOCATE y, x...!  Which to me is crazy.  When I gave up on Liberty BASIC (I felt ripped off on licensing too, which didn't help), I had to convert everything back.

So use LOCATE with caution, is my advice.

Malcolm

[Petr]

None problems with LOCATE. First set your text screen to correct values. Locate use is LOCATE  ROW, COLUMN

Code: QB64: [Select]

1. SCREEN _NEWIMAGE(100, 25, 0)
2.  
3. Location_x = 100
4. Location_y = 25
5.  
6. LOCATE Location_y, Location_x
7.  
8. PRINT "a nice test"
9.