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parameter table

Introduction

Before Codea version 1.5, parameter referred to a function. From version 1.5, it refers to a table of functions. Calling parameter as a function is deprecated and generates a warning message in the Output pane.

The 'Parameters' chapter of Codea's in-app reference documents the parameter functions.

parameter.number() constructors

When parameter.number() is called with two arguments, the second is interpreted as the maximum value of the slider and the minimum value defaults to 0. For example:

parameter.number("parameter1", 20)  -- Slider running from 0 to 20
parameter.number("parameter2", -20) -- Slider stuck at 0

Resetting previously set parameters

As documented in the in-app reference, all previously set parameters can be cleared using the parameter.clear() function. Once cleared, parameters can then be re-established, if required.

The example code below illustrates how the functionality of parameter(), iparameter() and clearParameters() can be extended to cause the extended functions to keep track of what parameters have previously been set and, consequently, allow other parameters to be reset automatically when a previously set parameter is reset.

do
    -- Preserve built-in functions
    local oldP = parameter
    local oldIP = iparameter
    local oldCP = clearParameters
    local pList = {}    -- Will hold the set i/parameters
    local pProp = {}    -- Will hold their properties

    -- Private generic helper
    local addP = function(isIParam, var, min, max, init)
        local old = oldP
        if isIParam then
            if init then init = math.modf(init) end
            if min then min = math.modf(min) end
            if max then max = math.modf(max) end
            old = oldIP
        end
        if not min then
            min = 0
            max = 1
            if isIParam then max = 10 end
        end
        if not max then
            max = math.max(0, min)
            min = 0
        end
        if not pProp[var] then
            if not init then init = min end
            pProp[var] = {
                min = math.min(min, init),
                max = math.max(max, init),
                isIParam = isIParam}
            pList[#pList+1] = var
            old(var, min, max, init)
            return
        end
        local p = pProp
        local l = pList
        p[var] = {
            min = min,
            max = max,
            isIParam = isIParam}
        clearParameters()
        for i = 1, #l do
            local k = l[i]
            local v = p[k] 
            local i = _G[k]
            if isIParam then i = math.modf(i) end
            if k == var and init then i = init end
            if v.isIParam then
                iparameter(k, v.min, v.max, i)
            else
                parameter(k, v.min, v.max, i)
            end
        end
        return
    end

    -- Redefine parameter()
    parameter = function (var, min, max, init)
        addP(false, var, min, max, init)
    end

    -- Redefine iparameter()    
    iparameter = function (var, min, max, init)
        addP(true, var, min, max, init)
    end

    -- Redefine clearParameters()
    clearParameters = function ()
        pProp = {}
        pList = {}
        oldCP()
        return
    end        
end

--
-- An example of the use of the extended functionality above
--
function setup()
    parameter("test1", 0, 100, 50)
    iparameter("itest1", 0, 100, 50)
    parameter("test2", 100, 200, 50)
    iparameter("itest2", 100, 200, 50)
    parameter("test3")   -- A default parameter
    iparameter("itest3") -- A default iparameter
end

function draw()
    background(40, 40, 50)
end

local hasBeenReset = false
function touched(touch)
    if touch.state == BEGAN and not hasBeenReset then
        parameter("test2", 0, 300)  -- Reset the limits of 'test2'
        iparameter("test1", 0, 100) -- Change 'test1' to an iparameter
        hasBeenReset = true
    end
end