strings.md

Strings

Concatenation

String + and string += lower to SF__.StrConcat__(...). The helper is emitted once into the output when needed:

function SF__.StrConcat__(...)
    local result = ""
    for i = 1, select("#", ...) do
        local part = select(i, ...)
        if part ~= nil then
            result = result .. tostring(part)
        end
    end
    return result
end

string msg = "damage:" + damage + " count:" + count;

local msg = SF__.StrConcat__("damage:", damage, " count:", count)

If a concatenated part has a C# ToString() override on its class type, SharpForge lowers that part to a nil-safe method call before it reaches SF__.StrConcat__(...).

string msg = "[" + unitName + "]";

local msg = SF__.StrConcat__("[", (function()
    local strPart = unitName
    if (strPart ~= nil) then
        return strPart:ToString()
    end
    return nil
end)(), "]")

If a concatenated or interpolated part has a C# ToString() override on a struct type, SharpForge lowers it through the struct's emitted type method using the flattened self-field ABI.

string msg = "[" + point + "]";

local msg = SF__.StrConcat__("[", SF__.Point.ToString(point__x, point__y), "]")

Interpolation

Interpolated strings lower to SF__.StrConcat__(...) calls. Parts with no format clause are passed directly, except operands with a C# ToString() override: class-typed parts lower through the nil-safe :ToString() wrapper used by string +, while struct-typed parts lower through the emitted flattened struct method call. Parts with a supported format clause lower to string.format(...).

string s = $"damage:{damage:F0} count:{count:D3} id:{id:X2}";

local s = SF__.StrConcat__("damage:", string.format("%.0f", damage), " count:", string.format("%03d", count), " id:", string.format("%02X", id))

Supported format specifiers: F/f (fixed-point), D/d (decimal integer), X/x (hexadecimal), each with optional width/precision digits. Any other .NET format string produces a transpiler error.

Verbatim Strings

Verbatim string literals (@"...") are supported and lower to Lua string literals.

Unsupported

string.Format(...), .ToString(format), and other .NET string methods not listed here produce a transpiler error.