modeling_library.jl

#############################
# probability distributions #
#############################

import Distributions
using SpecialFunctions: loggamma, logbeta, digamma

abstract type Distribution{T} end

"""
    val::T = random(dist::Distribution{T}, args...)

Sample a random choice from the given distribution with the given arguments.
"""
function random end

"""
    lpdf = logpdf(dist::Distribution{T}, value::T, args...)

Evaluate the log probability (density) of the value.
"""
function logpdf end

"""
    has::Bool = has_output_grad(dist::Distribution)

Return true of the gradient if the distribution computes the gradient of the logpdf with respect to the value of the random choice.
"""
function has_output_grad end

"""
    grads::Tuple = logpdf_grad(dist::Distribution{T}, value::T, args...)

Compute the gradient of the logpdf with respect to the value, and each of the arguments.

If `has_output_grad` returns false, then the first element of the returned tuple is `nothing`.
Otherwise, the first element of the tuple is the gradient with respect to the value.
If the return value of `has_argument_grads` has a false value for at position `i`, then the `i+1`th element of the returned tuple has value `nothing`.
Otherwise, this element contains the gradient with respect to the `i`th argument.
"""
function logpdf_grad end

is_discrete(::Distribution) = false # default

# NOTE: has_argument_grad is documented and exported in gen_fn_interface.jl

get_return_type(::Distribution{T}) where {T} = T

export Distribution
export random
export logpdf
export logpdf_grad
export has_output_grad
export is_discrete

# built-in distributions
include("distributions/distributions.jl")

# @dist DSL
include("dist_dsl/dist_dsl.jl")

# mixtures of distributions
include("mixture.jl")

# products of distributions
include("product.jl")

###############
# combinators #
###############

# code shared by vector-shaped combinators
include("vector.jl")

# built-in generative function combinators
include("choice_at/choice_at.jl")
include("call_at/call_at.jl")
include("map/map.jl")
include("unfold/unfold.jl")
include("recurse/recurse.jl")
include("switch/switch.jl")

#############################################################
# abstractions for constructing custom generative functions #
#############################################################

include("custom_determ.jl")