diff options
Diffstat (limited to 'dhall_core')
| -rw-r--r-- | dhall_core/src/core.rs | 34 |
1 files changed, 21 insertions, 13 deletions
diff --git a/dhall_core/src/core.rs b/dhall_core/src/core.rs index fa6fca4..03974eb 100644 --- a/dhall_core/src/core.rs +++ b/dhall_core/src/core.rs @@ -468,15 +468,24 @@ fn add_ui(u: usize, i: isize) -> usize { } } -/// Applies `shift` to a single var. -/// The first var is the var to shift away from; the second is the variable to shift -fn shift_var(delta: isize, var: &V<Label>, in_expr: &V<Label>) -> V<Label> { - let V(x, n) = var; - let V(y, m) = in_expr; - if x == y && n <= m { - V(y.clone(), add_ui(*m, delta)) - } else { - V(y.clone(), *m) +impl<Label: PartialEq + Clone> V<Label> { + pub fn shift(&self, delta: isize, var: &V<Label>) -> Self { + let V(x, n) = var; + let V(y, m) = self; + if x == y && n <= m { + V(y.clone(), add_ui(*m, delta)) + } else { + V(y.clone(), *m) + } + } + + pub fn shift0(&self, delta: isize, x: &Label) -> Self { + let V(y, m) = self; + if x == y { + V(y.clone(), add_ui(*m, delta)) + } else { + V(y.clone(), *m) + } } } @@ -492,12 +501,11 @@ pub fn shift<N, E>( ) -> SubExpr<N, E> { use crate::ExprF::*; match in_expr.as_ref() { - Var(v) => rc(Var(shift_var(delta, var, v))), + Var(v) => rc(Var(v.shift(delta, var))), _ => in_expr.map_subexprs_with_special_handling_of_binders( |e| shift(delta, var, e), |l: &Label, e| { - let vl = V(l.clone(), 0); - let newvar = shift_var(1, &vl, var); + let newvar = var.shift0(1, l); shift(delta, &newvar, e) }, ), @@ -567,7 +575,7 @@ fn subst_shift_inner<N, E>( let actual_var = V(x.clone(), add_ui(*n, *dn)); match in_expr.as_ref() { Var(v) if v == &actual_var => shift0_multiple(ctx, value), - Var(v) => rc(Var(shift_var(-1, &actual_var, v))), + Var(v) => rc(Var(v.shift(-1, &actual_var))), _ => in_expr.map_subexprs_with_special_handling_of_binders( |e| subst_shift_inner(ctx, var, value, e), |l: &Label, e| { |