Texas Instruments TI-89 Developer's Guide

616
Appendix A: System Routines — Graphing
TI
-
89 / TI
-
92 Plus Developer Guide
Not for Distribution
Beta Version January 26, 2001
YCvtPtoF
Declaration:
BCD16
YCvtPtoF
(SSHORT
y
, GR_WIN_VARS *
ptr
)
Category:
Graphing
Description:
Converts pixel row number
y
to the corresponding floating point y
coordinate at the center of that row, based on the specified graph viewing
window.
Inputs:
y
— Row number. The topmost row is row 0 in all graph windows.
Valid row numbers are not limited to the actual window height,
allowing computation for off-screen values above (negative row
number) or below the visible window.
ptr
— Pointer to the GR_WIN_VARS struct to use for viewing window
values (
gr_active
for the active graph window,
gr_other
for the
second graph in two graph mode).
Outputs:
Returns the y coordinate at the center of row
y
in BCD16 floating-point
format, rounded to 12 digits.
Assumptions:
Assumes an x, y coordinate system, even in 3D mode.
Side Effects:
Possible overflow error.
Availability:
All versions of the TI-89 / TI-92 Plus.
TI
-
89 / TI
-
92 Plus
Differences:
None
See Also: XCvtFtoP, CptFuncX, XCvtPtoF, YCvtFtoP
Example:
GetWinCursor( gr_active->grwinp, &col, &row );
/* find BCD x, y coordinates corresponding to current free-moving cursor */
x = XCvtPtoF( col, gr_active );
y = YCvtPtoF( row, gr_active );

Texas Instruments TI-89 Specifications

General

Display size (HxV)	100 x 160 mm
Memory type	639K FLASH ROM, 188K bytes RAM
Compatible operating systems	Operating System 2.09
Battery type	AAA