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\DOC tysubst
\TYPE {tysubst : (hol_type * hol_type) list -> hol_type -> hol_type}
\DESCRIBE
The call {tysubst [ty1',ty1; ... ; tyn',tyn] ty} will systematically traverse
the type {ty} and replace the topmost instances of any {tyi} encountered with
the corresponding {tyi'}. In the (usual) case where all the {tyi} are type
variables, this is the same as {type_subst}, but also works when they are not.
\FAILURE
Never fails. If several {tyi} are the same, the first one in the list will be
used to determine the substitution.
\EXAMPLE
{
# tysubst [`:num`,`:A`; `:bool`,`:B`] `:A->(B)list->A#B#C`;;
val it : hol_type = `:num->(bool)list->num#bool#C`
# tysubst [`:A`,`:(num)list`] `:num->(num)list->(num)list`;;
val it : hol_type = `:num->A->A`
}
\SEEALSO
inst, type_subst.
\ENDDOC
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