31 lines
1 KiB
Lua
31 lines
1 KiB
Lua
-- Parse a template expression string 'str'.
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-- The string 'str' may contain placeholders of the form '% i', where 'i' is a numeral.
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-- The placeholders are replaced with values from the array 'arg_array'.
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local arg_array = {}
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-- We implement this feature using macros available in Lean.
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macro("%",
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{ macro_arg.Int },
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function (env, i)
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if i <= 0 then
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error("invalid template argument reference %" .. i .. ", first argument is 1")
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elseif i > #arg_array then
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error("invalid template argument reference %" .. i .. ", only " .. tostring(#arg_array) .. " argument(s) were provided")
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else
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return arg_array[i]
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end
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end
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)
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-- Parse a template.
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-- Example:
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-- r = parse_template("%1 + %2 + %1", {Const("a"), Const("b")})
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-- print(r)
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-- >> a + b + a
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function parse_template(str, args, env, opts, fmt)
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assert(type(str) == "string")
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assert(type(args) == "table")
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assert(env == nil or is_environment(env))
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arg_array = args
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return parse_lean(str, env, opts, fmt)
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end
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