Values & lists

Numbers

Vision has whole numbers and decimals. Underscores in number literals are allowed for readability and ignored by the compiler.

a count is 42
a ratio is 0.618
a big is 1_000_000    // underscores for readability

Text

Text values are written in double quotes. Text interpolation embeds an expression with curly braces: "{the name}" splices the value of the name into the string at that position.

a name is "Marigold"
a path is "/home/june/notes.txt"
a greeting is "hello, {name}"   // text interpolation

Text is immutable. To build text up piece by piece, collect pieces in a list and join them. Joining with followed by works for two pieces at a time.

Lists

A list from known values uses are. An empty growable list uses a list of. Positions are 1-based — position 1 is the first value.

favorite numbers are 4, 8, 15, 16, 23, 42
the samples are a list of decimals

add 0.5 to the samples
the third is the value at 3 in favorite numbers
the head is the first value in favorite numbers
the count is how many are in favorite numbers

for each number in favorite numbers
    say number

add appends to the end. There is no index-based write — to change a value at a position, build a new list.

Bytes

A byte is a whole number from 0 to 255. A list of bytes holds raw binary data and is used when talking to C libraries or reading/writing files.

the data is a list of bytes
add 255 to the data
add 0 to the data

Described things

A described thing is a named bundle of fields (a struct). Declare it with a Name has:, then list the fields. Read a field with the field of the thing; write it with set the field of the thing to.

a Point has:
    an x
    a y

the origin is a Point
set the x of the origin to 0
set the y of the origin to 0

Named sets

A named set is an enumeration (an enum). Declare it with a Name is one of. Check membership with is one of.

a Direction is one of north, south, east, west

if the heading is one of north, south
    say "going vertical"