diff options
| author | bnewbold <bnewbold@robocracy.org> | 2016-04-25 23:29:08 -0400 |
|---|---|---|
| committer | bnewbold <bnewbold@robocracy.org> | 2016-04-25 23:29:08 -0400 |
| commit | 4b11d9fbd2b4ef0bc4fd3bfba18c3bd2ce10ea73 (patch) | |
| tree | 871d8440f84502a514f0ccbd33fc01c286a022c3 /rust | |
| parent | 6880d8194a03152fdb293565000efa7149aa0929 (diff) | |
| download | spectrum-4b11d9fbd2b4ef0bc4fd3bfba18c3bd2ce10ea73.tar.gz spectrum-4b11d9fbd2b4ef0bc4fd3bfba18c3bd2ce10ea73.zip | |
rust: more car/cdr/cons tweaks (still needs review)
Diffstat (limited to 'rust')
| -rw-r--r-- | rust/spectrum.rs | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/rust/spectrum.rs b/rust/spectrum.rs index b61e3ad..3a0362f 100644 --- a/rust/spectrum.rs +++ b/rust/spectrum.rs @@ -520,7 +520,7 @@ fn apply_action(list: &Vec<SchemeExpr>, &SchemeExpr::SchemeList(ref list) => { Ok(list[0].clone()) }, - _ => Err(format!("cdr only takes lists")) + _ => Err(format!("car only takes lists")) } }, "cdr" => { @@ -529,9 +529,13 @@ fn apply_action(list: &Vec<SchemeExpr>, } match &args[0] { &SchemeExpr::SchemeList(ref list) => { - Ok(SchemeExpr::SchemeList(list[1..].to_vec())) + if list.len() > 1 { + Ok(SchemeExpr::SchemeList(list[1..].to_vec())) + } else { + Ok(SchemeExpr::SchemeNull) + } }, - _ => Err(format!("car only takes lists")) + _ => Err(format!("cdr only takes lists")) } }, "cons" => { @@ -539,12 +543,15 @@ fn apply_action(list: &Vec<SchemeExpr>, return Err(format!("cons takes two arguments")); } match &args[1] { + &SchemeExpr::SchemeNull => { + Ok(SchemeExpr::SchemeList(vec![args[0].clone()])) + }, &SchemeExpr::SchemeList(ref list) => { let mut ret = vec![args[0].clone()]; ret.extend_from_slice(list); Ok(SchemeExpr::SchemeList(ret)) }, - _ => Err(format!("cdr takes only lists")) + _ => Err(format!("cons second arg must be list or null")) } }, "display" => { |