Vocabulary#

Every word of the language, and what it means.

The vocabulary of .vis 0.1. The grammar is in Language reference; the normative text in Language specification.

Keywords#

Reserved everywhere: they cannot name anything.

Keyword	Meaning
`param`	declares a numeric constant of the program: param alpha = 0.2
`canvas`	declares a grid of cells and its channels: canvas plate[256, 256] edge clamp { temperature }
`kernel`	declares the update of every cell of a canvas: kernel diffuse on plate { … }
`measure`	declares one number over a whole canvas: measure total = sum(t) on plate
`run`	the block of commands that runs the simulation, the last part of a program
`repeat`	runs a block of commands n times: repeat 100 { diffuse }
`scenarios`	runs a block n times from the same state, with scenario = 0 … n − 1
`save`	writes a channel (.png, .npy, .vti), a whole canvas (.vti) or the series of a measure (.csv)
`print`	shows a measure, a summary of a channel or one cell
`load`	reads real data into a channel (.npy, .csv, .txt, .asc, .png)
`let`	declares an immutable local variable
`var`	declares a mutable local variable
`if`	runs a block where a condition holds
`else`	the alternative of an if
`for`	repeats a block for an integer range, both ends included: for i in -1 to 1 { … }
`in`	part of for
`and`	true when both conditions are
`or`	true when either condition is
`not`	negates a condition
`true`	the true condition
`false`	the false condition

They have a meaning in one place only; elsewhere they are ordinary names.

Word	Where
`on`	kernel name on canvas, measure … on canvas
`to`	for i in a to b
`edge`	canvas name[w, h] edge clamp
`where`	measure … on canvas where condition
`nodata`	load c.t “dem.asc” nodata 0: the value of the cells without data
`f32`	a channel of 32-bit floats (the default)
`i32`	a channel of 32-bit integers

From the lowest precedence to the highest.

Operators	Level	Meaning
`or`	1	logical or of two conditions
`and`	2	logical and of two conditions
`not`	3	logical negation (prefix)
`==` `!=` `<` `<=` `>` `>=`	4	comparison of two numbers (== and != also of two conditions); does not chain
`+` `-`	5	addition, subtraction
`*` `/` `%`	6	multiplication; / is always real division (7 / 2 = 3.5), within 1.15 ULP, with 1 / 0 = MAX, −1 / 0 = −MAX and 0 / 0 = 0; % is the remainder, with the sign of the dividend
`-` (prefix)	7	negation
`^`	8	power, right-associative; x ^ n with an integer literal n ≤ 16 is an exact product

Compound assignments: +=, -=, *=, /=.

Type	Values
`float`	a 32-bit floating-point number, always finite: an overflow gives ±3.4028235e38
`int`	a 32-bit integer; arithmetic wraps around (two’s complement)
`bool`	true or false: the result of a comparison; not a number

Channel types: f32, float channel (the default); i32, integer channel: exact totals with flux().

Read-only, inside kernels and measures.

Name	Value
`x`	the column of the cell, from 0, growing to the right
`y`	the row of the cell, from 0, growing downwards
`z`	the layer of the cell, from 0 (only in a 3-D canvas)
`width`	the number of columns of the canvas
`height`	the number of rows of the canvas
`depth`	the number of layers (only in a 3-D canvas)
`scenario`	the index of the scenario inside a scenarios block, from 0; 0 outside

Edge	Reading outside the canvas
`clamp`	outside the canvas reads the nearest border cell (the default)
`wrap`	outside the canvas reads the opposite side (a torus)
`zero`	outside the canvas reads 0

Reduction	Value
`sum`	the sum of a number over the cells (about 44 bits of precision)
`mean`	the mean of a number over the cells
`min`	the smallest value
`max`	the largest value
`count`	the number of cells where a condition holds

Command	Effect
`name`	runs a kernel (one step) or takes a measure (one value of its series)
`repeat n { ... }`	runs the commands n times
`scenarios n { ... }`	runs the commands n times from the same state, with scenario = 0 … n − 1; not nested
`load canvas.channel "file" [nodata v]`	reads real data into a channel
`save canvas.channel "file"`	writes a channel: .png (colour map), .npy (raw values) or .vti (VTK)
`save canvas "file.vti"`	writes every channel of a canvas into one VTK file
`save measure "file.csv"`	writes the series of a measure
`print measure`	shows a measure (and its distribution over scenarios)
`print canvas.channel [x, y]`	shows a summary of a channel, or one cell

load reads .npy, .csv, .txt, .asc, .png; save writes .png, .npy, .vti and the .csv series of a measure.