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Language & UI

Multiple dispatch

user-overloadable functions, dispatched on type.

catalog/qu_multiple_dispatch.qu

Defines the SAME function name multiple times, once per parameter type tag; each call runs whichever overload's tags match its actual argument types (Qu's multiple-dispatch surface, phase 1-3).

What it exercises

How it works

Overloaded on one argument

function describe(x: vec)
    print "vec of length {length(x)}, sum={sum(x)}"
end function

function describe(x: mat)
    print "mat {rows(x)}x{cols(x)}"
end function

function describe(x: num)
    print "num {x}"
end function

function describe(x: str)
    print "string \"{x}\""
end function

describe([1, 2, 3])
describe([1, 2; 3, 4])
describe(42)
describe("hello")

Overloaded on two arguments, plus an untyped fallback

function combine(a: num, b: num)
    print "num+num -> {a + b}"
end function

function combine(a: vec, b: vec)
    print "vec+vec -> {a + b}"
end function

function combine(a, b)
    print "fallback: no specific overload for this pair"
end function

combine(2, 3)
combine([1, 2, 3], [10, 20, 30])
combine("x", true)   # falls through to the untyped overload

Results

printed
vec of length 3, sum=6
mat 2x2
num 42
string "hello"
num+num -> 5
vec+vec -> [11, 22, 33]
fallback: no specific overload for this pair

The whole program

Runnable as it stands: qu run catalog/qu_multiple_dispatch.qu

# qu_multiple_dispatch.qu — user-overloadable functions, dispatched on type.

#

# Defines the SAME function name multiple times, once per parameter type

# tag; each call runs whichever overload's tags match its actual argument

# types (Qu's multiple-dispatch surface, phase 1-3).

#

# Constructs exercised (all real, verified-working syntax):

#   function name(x: vec) / (x: mat) / (x: num) — type-tagged overloads

#   dispatch on TWO parameters at once (describe_pair)

#   a plain, untyped fallback overload


backend auto

#%% Overloaded on one argument

function describe(x: vec)
    print "vec of length {length(x)}, sum={sum(x)}"
end function

function describe(x: mat)
    print "mat {rows(x)}x{cols(x)}"
end function

function describe(x: num)
    print "num {x}"
end function

function describe(x: str)
    print "string \"{x}\""
end function

describe([1, 2, 3])
describe([1, 2; 3, 4])
describe(42)
describe("hello")

#%% Overloaded on two arguments, plus an untyped fallback

function combine(a: num, b: num)
    print "num+num -> {a + b}"
end function

function combine(a: vec, b: vec)
    print "vec+vec -> {a + b}"
end function

function combine(a, b)
    print "fallback: no specific overload for this pair"
end function

combine(2, 3)
combine([1, 2, 3], [10, 20, 30])
combine("x", true)   # falls through to the untyped overload