//x must be global.
//Might as well make y global.
F64 x,y,y_last;
U0 Cartesian()
{
U8 *st;
I64 ch=0,h,v;
Bool first;
CDC *dc=DCAlias;
do {
DocClear;
"Enter algebraic equation to graph.\n"
"Example: y=2*x\n"
"y=";
if (st=GetStr) {
if (*st) {
h=Fs->pix_width/2;
v=Fs->pix_height/2;
dc->color=RED;
GrLine(dc,h,0,h,2*v+1);
GrLine(dc,0,v,2*h+1,v);
first=TRUE;
dc->color=BLACK;
for (x=-h;x<=h;x++) {
y=-ExePrint("ToF64(%s);",st)(F64);
if (!first)
GrLine(dc,x-1+h,y_last+v,x+h,y+v);
y_last=y;
first=FALSE;
}
ch=GetChar;
} else
ch=CH_SHIFT_ESC;
Free(st);
} else
ch=CH_SHIFT_ESC;
DCFill;
} while (ch!=CH_SHIFT_ESC && ch!=CH_ESC);
DCDel(dc);
}
Cartesian;
//For better performance, compile the expression entered by the
//user one time with LexExpression2Bin() and use Call().
//See /Demo/CompileDemo.HC.