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Foldr MaSH docs v11.2.0.0

Collections

A collection holds many values under one name. MaSH has two basic kinds, arrays and dictionaries, and a toolkit called mash.collect for working on them.

Arrays

Section titled “Arrays”

An array is an ordered list in square brackets:

set colours to ["red", "green", "blue"]
printline colours[0]
printline colours[2]
printline count(colours)
red
blue
3

Positions start at 0, so the first item is colours[0]. count() tells you how many items there are. (Arrays have no .length.)

Change an item by its position, and add one to the end with []:

set colours to ["red", "green"]
set colours[0] to "pink"
colours[] = "blue"
printline colours
Array [
    "pink",
    "green",
    "blue"
]

Arrays can hold anything, including other arrays:

set grid to [[1, 2], [3, 4]]
printline grid[1][0]
3

Dictionaries

Section titled “Dictionaries”

A dictionary stores values under names, called keys. Use curly braces:

set person to {name: "Ada", age: 36}
printline person["name"]
printline person.age
Ada
36

Read a value with ["key"] or with a dot. Add or change one the same way:

set person to {name: "Ada"}
set person["age"] to 36
set person.city to "London"
printline person
Dictionary {
    "name": "Ada",
    "age": 36,
    "city": "London"
}

Reading a key that isn’t there gives null, not an error. That makes ?? a good fit:

set person to {name: "Ada"}
printline person["phone"] ?? "no phone on file"
no phone on file

Dictionaries can nest, and an array can hold dictionaries. This is the shape of most data you’ll get from files and web services:

set orders to [
    {ref: "A-1", total: 40},
    {ref: "A-2", total: 15}
]
each orders as order
    printline "{{order.ref}}: {{order.total}}"
end
A-1: 40
A-2: 15

mash.collect

Section titled “mash.collect”

Wrap an array or dictionary in mash.collect() and you get a Collection with lots of helper methods. Many of them take a block of script, which is a small piece of code run once per item. You’ll write blocks properly in Blocks. For now, copy the shape.

Totals and joins

Section titled “Totals and joins”
set prices to mash.collect([12, 30, 8])
printline prices.sum()
printline prices.max()
printline prices.min()
printline prices.avg()
printline prices.count()
printline prices.join(", ")
50
30
8
16.666666666667
3
12, 30, 8

Filtering

Section titled “Filtering”

filter keeps the items for which the block returns true:

set people to mash.collect([
    {name: "Ada", age: 36},
    {name: "Bo", age: 17},
    {name: "Cy", age: 52}
])
set adults to people.filter(block person
    return person["age"] is more than or equal to 18
end)
printline adults.count()
printline adults.pluck("name").join(" and ")
2
Ada and Cy

pluck pulls one key out of every item. sum("age") adds up one key. where is a shortcut for simple matches:

set people to mash.collect([
    {name: "Ada", team: "x", age: 36},
    {name: "Bo", team: "y", age: 17},
    {name: "Cy", team: "x", age: 52}
])
printline people.sum("age")
printline people.where("team", "x").count()
printline people.sortBy("age").first()["name"]
printline people.sortByDesc("age").first()["name"]
105
2
Bo
Cy

Changing every item

Section titled “Changing every item”

map builds a new collection from the results of a block:

set names to mash.collect(["ada", "bo"])
set shouted to names.map(block n
    return mash.str(n).upper().toString()
end)
printline shouted.join(", ")
ADA, BO

Sorting

Section titled “Sorting”
set n to mash.collect([5, 2, 8])
printline n.sort().values().join(", ")
printline n.sortDesc().values().join(", ")
2, 5, 8
8, 5, 2

A sorted collection remembers where each item used to sit. Add .values() before you print or join so the order is tidy.

Looping over a collection

Section titled “Looping over a collection”

A collection works in each just like an array:

set people to mash.collect([{name: "Ada"}, {name: "Bo"}])
each people as person
    printline person["name"]
end
Ada
Bo

Many of the things MaSH gives back, such as a list of files, are collections. You can filter, sort and total them with the methods above.

A plain dictionary takes the same methods. person.has("name") and person.keys() work, and person.remove("name") changes person itself.

set person to {name: "Ada", role: "admin"}
printline person.has("name")
person.remove("role")
printline person.keys()
true
Array [
    "name"
]

Try it

Section titled “Try it”

Make an array of five numbers. Print the total, the biggest, and a list of only the ones above 10.

Next, you’ll learn to write your own reusable pieces.