{ 5 } [ -2/3 -2 { 1 3 } calc-y ] unit-test
{ 3 } [ -2/3 1 { -2 5 } calc-y ] unit-test
{ 5 } [ -2/3 -2 { -2 5 } calc-y ] unit-test
+{ 5 } [ -2 { 1 3 } { -2 5 } y-at ] unit-test
+{ 3 } [ 1 { 1 3 } { -2 5 } y-at ] unit-test
+{ 1 } [ 4 { -2 5 } { 1 3 } y-at ] unit-test
+{ 0.0 } [ 5.5 { -2 5 } { 1 3 } y-at ] unit-test
{ 2 3 } [ { 1 2 3 } last2 ] unit-test
{ 1 2 } [ { 1 2 } last2 ] unit-test
: calc-line-slope ( point1 point2 -- slope ) v- first2 swap / ;
: calc-y ( slope x point -- y ) first2 [ - * ] dip + ;
+: y-at ( x point1 point2 -- y ) dupd calc-line-slope -rot calc-y ;
: last2 ( seq -- penultimate ultimate ) 2 tail* first2 ;
! Due to the way adjusted-tail-slice works, the first element of
! > min. Otherwise the first one would be = min.
: left-cut ( min pairs -- seq )
2dup first first < [
- [ dupd first2 dupd calc-line-slope -rot calc-y 2array ] keep
- rest-slice swap prefix
+ [ dupd first2 y-at 2array ] keep rest-slice swap prefix
] [
nip
] if ;
! last is < max. Otherwise the last one would be = max.
: right-cut ( max pairs -- seq )
2dup last first < [
- [ dupd last2 dupd calc-line-slope -rot calc-y 2array ] keep
- but-last-slice swap suffix
+ [ dupd last2 y-at 2array ] keep but-last-slice swap suffix
] [
nip
] if ;