ftd.calculator

[amitu]

Currently if we define a variable, x, it's not possible to show the definition of x in a page.

For data often it is desirable to see the data definitions:

And ftd.calculator shows these variables and their values side by side.

-- ftd.calculator: rent calculation

-- monthly-rent: 10

Rent per month

-- months: 5

We lived there from jan to may.

-- total-rent: monthly-rent * months

Since this is calculator we only define numbers so not type annotations. 

-- end: ftd.calculator 

Custom Rendering

Calculator will require two ftd.ui elements, one to wrap the entire body, and show caption, and other to show individual steps.

Since this feature is a language level feature, based on calculator we have to change the parser itself, we can not wrap ftd.calculator in other components. So we must provide the customisation as a parameters:

-- component my-calculator-view:
ftd.calculator-data data:
integer foo:

-- end: my-calculator-view

-- ftd.calculator: some calculations
renderer: my-calculator-view  ;; other possible keyword: delegate
foo: 20

-- end: ftd.calculator

We can ensure that extra arguments can be passed as well, eg foo.

Named Calculator

Calculators can be given names, and then variables defined in them can be accessed from outside:

-- ftd.calculator rent: rent calculations

-- monthly-rental: 20

-- end: ftd.calculator

-- ftd.number: $rent.monthly-rental

Including External Definitions

Sometimes a variable may be defined outside the calculator, or in other modules, you can include them as step by using:

-- integer x: 20
-- ftd.calc:

-- a: 20
-- include x:

Optional description of x.

-- include: foo.com/bar.x as y

-- end: ftd.calc

Once a variable has been included, it can be modified during calculation steps.

Hiding Steps

A step can be hidden by doing:

-- ftd.calc:

-- radius: 20
-- pi: 3.14
hidden: true

No need to show definition of pi, we are going to show pi as symbolic only.

-- area: pi * (radius^2)

-- end: ftd.calc

ftd.calculator-data type

-- record ftd.calculator-data:
optional string caption:
ftd.step list steps: 

-- record ftd.step:
string name:
string expression:
string value:
option string body:
boolean hidden:

Step Delegation

Along with renderer we can also pass step-renderer. If step-renderer is used, the arguments of step renderers can be included in the step definitions.

-- component my-step-renderer:
integer foo:

-- ftd.calc
step-renderer: my-step-renderer

-- x: 20
foo: 3

-- end: ftd.calc

Here we can pass foo to definition of x because step-renderer is my-step-renderer, which accepts foo.