Purl Language Reference

Syntax.

Reverse polish notation separated by colon.

Literal.

Number

ex. 1, -1.5, 1E3

Operator

ex. mul, to.png

String

You can use “::” for single colon(“:”) in string literal.

ex. (Hello World), (http:://www.yahoo.com/)

Stack Operation.

op1 op2 swap op2 op1

swap two values on the stack.

op pop

pop the top element of the stack.

… n get result

get n-th element from the top of the stack.

… n pull result

bring the n-th element from the top of the stack to the top.

… n length slice result

bring the elements starting at n-th element to the top for length elements.

op dup op op

duplicate op.

… n reverse result

reverse the top n elements.

… m n stripe result

encode the top m × n elements into m × n matrix, transpose it and serialize it into n × m elements.

Conversion.

image to.png binary content-type

convert image to PNG stream.

image to.jpg binary content-type

convert image to JPEG stream.

image to.jpeg binary content-type

convert image to JPEG stream.

image to.gif binary content-type

convert image to GIF stream.

… n to.json binary content-type

pack last n elements to JSON array.

Image Operation.

id load image

load image from database.

image geom image width height

image x y width height crop image

image angle rotate image

image x1 y1 x2 y2 extend image

image1 image2 composite image

composite two images.

Effect Operation.

image radius blur image

image radius shadow image

image radius round image

image opacity opacify image

image radius dropshadow image

is swap:dup:2:pull:shadow:swap:composite

Resize Operation.

image width height resize image

resize image.

image width height resize.upto image

resize image preserving aspect ratio.

image width height resize.fitto image

resize image preserving aspect ratio.

Resize Macros.

image large image

image medium image

image small image

Arithmetic.

op1 op2 add result

op1 + op2

op1 op2 sub result

op1 – op2

op1 op2 mul result

op1 * op2

op1 op2 div result

op1 / op2

op1 op2 mod result

op1 mod op2

Cairo.

width height ctx context

prepare cairo surface and return context.

context ctx image

rendering to image.

context r g b rgb context

set current color.

context width linewidth context

set line-width.

context x y moveto context

move current point to x, y.

context x y lineto context

line to x, y.

context x y radius angle1 angle2 arc context

context x y radius angle1 angle2 arc.cw context

add arc to current path. begins at angle1(degree) to angle2(degree) clockwise.

context x y radius begin end arc.ccw context

add arc to current path. begins at angle1(degree) to angle2(degree) counterclockwise.

context x y radius circle context

add circle to current path.

context stroke context

draw current path.

context fill context

fill current path.

Macro.

( operators )

define macro.

Lmabda Operation.

… macro call result

expand macro.

… macro n times result

expand macro n times.

… macro n each result

expand macro after each of the top n elements.

… macro m n each.n result

expand macro after each group of m of the top n groups.

… macro m n each.stripe result

is equivalent to m n stripe macro m n each.n.

Arithmetic(Vector) – obsolete.

use Lambda module.

op1 op2 num add.2 result1 result2

op1 + num, op2 + num

op1 op2 num sub.2 result1 result2

op1 – num, op2 – num

op1 op2 num mul.2 result1 result2

op1 * num, op2 * num

op1 op2 num div.2 result1 result2

op1 / num, op2 / num

op1 op2 num mod.2 result1 result2

op1 mod num, op2 mod num