The unpac monorepo manager self-hosting as a monorepo using unpac
Fix example of external C function in the manual (#9977)
authored by
Greta Yorsh
and committed by
GitHub
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manual/manual/cmds/intf-c.etex
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manual/manual/cmds/intf-c.etex
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\end{alltt}
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This defines the value name \var{name} as a function with type
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\var{type} that executes by calling the given C function.
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For instance, here is how the "int_of_string" primitive is declared in the
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For instance, here is how the "seek_in" primitive is declared in the
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standard library module "Stdlib":
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\begin{verbatim}
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external int_of_string : string -> int = "caml_int_of_string"
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external seek_in : in_channel -> int -> unit = "caml_ml_seek_in"
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\end{verbatim}
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Primitives with several arguments are always curried. The C function
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does not necessarily have the same name as the ML function.
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The arity (number of arguments) of a primitive is automatically
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determined from its OCaml type in the "external" declaration, by
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counting the number of function arrows in the type. For instance,
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"input" above has arity 4, and the "input" C function is called with
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four arguments. Similarly,
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"seek_in" above has arity 2, and the "caml_ml_seek_in" C function
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is called with two arguments. Similarly,
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\begin{verbatim}
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external input2 : in_channel * bytes * int * int -> int = "input2"
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external seek_in_pair: in_channel * int -> unit = "caml_ml_seek_in_pair"
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\end{verbatim}
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has arity 1, and the "input2" C function receives one argument (which
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is a quadruple of OCaml values).
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has arity 1, and the "caml_ml_seek_in_pair" C function receives one argument
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(which is a pair of OCaml values).
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Type abbreviations are not expanded when determining the arity of a
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primitive. For instance,