usr/src/local/ditroff/ditroff.okeeffe/chem/chem.macros.src

# macros for chem; 1.1  (CWI)   87/03/31

pi = 3.141592654
deg = 57.29578
# cr = 0.08             # radius of invis circle at ring vertices (see cr[vh])
# crh = 0.16; crw = 0.12 # ht & wid of invis ellipse around atoms at ring vertices
# dav = 0.015           # vertical shift up for atoms in atom macro

# atom(text, wid, ht, carbon position, crh, crw, dav)
define atom { [
        T: $1 wid $2 ht $3-2*$7
        C: ellipse invis ht $5 wid $6 at T.w + ($4,$7)
        L: ellipse invis ht $5 wid $6 at T.w + (cwid/2,$7)
        R: ellipse invis ht $5 wid $6 at T.e + (-cwid/2,$7)
] }

# bond(length, angle in degrees, whatever)
define bond {
        line $3 by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
}

# fancy bonds:  r, theta, from/at
define doublebond {
        line $3 invis by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
        V1: last line.start; V2: last line.end; dx = V2.x-V1.x; dy = V2.y-V1.y
        norm = sqrt(dx*dx + dy*dy)
        ny = dx * .02 / norm
        nx = -dy * .02 / norm
        line from V1 + (nx,ny) to V2 + (nx,ny)
        line from V1 - (nx,ny) to V2 - (nx,ny)
        move to V2
}
define triplebond {
        line $3 invis by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
        V1: last line.start; V2: last line.end; dx = V2.x-V1.x; dy = V2.y-V1.y
        norm = sqrt(dx*dx + dy*dy)
        ny = dx * .025 / norm
        nx = -dy * .025 / norm
        line from V1 + (nx,ny) to V2 + (nx,ny)
        line from V1 - (nx,ny) to V2 - (nx,ny)
        line from V1 to V2
        move to V2
}
define backbond {
        line $3 invis by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
        V1: last line.start; V2: last line.end; dx = V2.x-V1.x; dy = V2.y-V1.y
        norm = sqrt(dx*dx + dy*dy)
        n = norm / .025
        ny = dx * .02 / norm
        nx = -dy * .02 / norm
        for i = 1 to n-1 do {
                XZ: i/n <V1,V2>
                line from XZ + (nx,ny) to XZ - (nx,ny)
        }
        move to V2
}
define frontbond {
        line $3 invis by ($1) * sin(($2)/deg), ($1) * cos(($2)/deg)
        V1: last line.start; V2: last line.end; dx = V2.x-V1.x; dy = V2.y-V1.y
        ah = arrowht; aw = arrowwid; ahead = arrowhead
        arrowht = sqrt(dx*dx + dy*dy)
        arrowwid = 0.05
        arrowhead = 7
        line <- from V1 to V2
        arrowht = ah; arrowwid = aw; arrowhead = ahead
}