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\DOC vsubst
\TYPE {vsubst : (term * term) list -> term -> term}
\SYNOPSIS
Substitute terms for variables inside a term.
\DESCRIBE
The call {vsubst [t1,x1; ...; tn,xn] t} systematically replaces free instances
of each variable {xi} inside {t} with the corresponding {ti} from the
instantiation list. Bound variables will be renamed if necessary to avoid
capture.
\FAILURE
Fails if any of the pairs {ti,xi} in the instantiation list has {xi} and {ti}
with different types, or {xi} a non-variable. Multiple instances of the same
{xi} in the list are not trapped, but only the first one will be used
consistently.
\EXAMPLE
Here is a relatively simple example
{
# vsubst [`1`,`x:num`; `2`,`y:num`] `x + y + 3`;;
val it : term = `1 + 2 + 3`
}
\noindent and here is a more complex instance where renaming of bound variables
is needed:
{
# vsubst [`y:num`,`x:num`] `!y. x + y < x + y + 1`;;
val it : term = `!y'. y + y' < y + y' + 1`
}
\COMMENTS
An analogous function {subst} is more general, and will substitute for free
occurrences of any term, not just variables. However, {vsubst} is generally
much more efficient if you do just need substitution for variables.
\SEEALSO
inst, subst.
\ENDDOC
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