RPIC

Variables & macros

pic is a real little language: variables, arithmetic, macros, loops and conditionals — all in service of describing pictures.

Environment variables

Every default is a variable you can set: boxwid, boxht, circlerad, linewid, arrowht, textht, linethick, fillval, scale and friends. Assignments take effect for everything drawn afterwards.

Open in Studio
.PS
boxht = 0.4
box "default"
move
boxwid = 0.62; linethick = 1.8
box "custom"
move
box "same"
.PE
default custom same

Variables are global — an assignment inside a block or macro propagates out, exactly as in dpic.

Expressions

Full arithmetic with + - * / %, comparisons, and the builtin functions sqrt sin cos atan2 log exp int max min rand:

Open in Studio
.PS
n = 6
for i = 0 to n-1 do {
circle rad 0.09 at (0.55*cos(i*6.2832/n), 0.55*sin(i*6.2832/n))
}
.PE

define

Macros take up to nine arguments ($1…$9) and expand inline — they are the reuse mechanism for geometry and for styles:

Open in Studio
.PS
define node { circle rad 0.2 $1 shaded "honeydew" outlined "darkgreen" }
define warn { outlined "firebrick" dashed }
node("a"); arrow; node("b"); arrow
box "c" wid 0.45 ht 0.4 warn()
.PE
a b c

for and if

Open in Studio
.PS
for i = 1 to 4 do {
box wid 0.4 ht 0.3 sprintf("%g", i)
if i < 4 then { arrow right 0.35 }
}
.PE
1 2 3 4

for … by * step multiplies instead of adding — handy for log scales.

sprintf and print

sprintf formats numbers into strings for labels; print writes to the diagnostic stream (stderr in the CLI) — the classic debugging tool.

Open in Studio
.PS
x = sqrt(2)
box sprintf("sqrt(2) = %.4f", x) wid 1.5
.PE
sqrt(2) = 1.4142

copy

copy "file.pic" includes another file — how the circuit corpus shares its macro shim. Paths resolve relative to the source file.

Where to go next