simplify reduce primitives

add tests for 0 and 1-length lists to reduce
SteelSeries · Feb 28, 2019 · 813d860 · 813d860
1 parent bcc926f
commit 813d860
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Showing 2 changed files with 41 additions and 35 deletions.
diff --git a/prim_list_functions.go b/prim_list_functions.go
@@ -259,17 +259,11 @@ func ReduceLeftImpl(args *Data, env *SymbolTableFrame) (result *Data, err error)
  return
  }
 
- length := Length(col)
- if length == 0 {
+ list := ToArray(col)
+ if len(list) == 0 {
  return initial, nil
  }
 
- if length == 1 {
- return Car(col), nil
- }
-
- list := ToArray(col)
-
  result, err = reduceFoldProc(list[0], list[1:], f, env, false)
 
  return
@@ -290,17 +284,11 @@ func ReduceRightImpl(args *Data, env *SymbolTableFrame) (result *Data, err error
  return
  }
 
- length := Length(col)
- if length == 0 {
+ list := ToArray(col)
+ if len(list) == 0 {
  return initial, nil
  }
 
- if length == 1 {
- return Car(col), nil
- }
-
- list := ToArray(col)
-
  result, err = reduceFoldProc(list[len(list)-1], list[:len(list)-1], f, env, true)
 
  return
@@ -316,6 +304,11 @@ func FoldLeftImpl(args *Data, env *SymbolTableFrame) (result *Data, err error) {
  initial := Second(args)
  col := Third(args)
 
+ if !ListP(col) {
+ err = ProcessError("fold-left needs a list as its third argument", env)
+ return
+ }
+
  list := ToArray(col)
 
  result, err = reduceFoldProc(initial, list, f, env, false)
@@ -333,6 +326,11 @@ func FoldRightImpl(args *Data, env *SymbolTableFrame) (result *Data, err error)
  initial := Second(args)
  col := Third(args)
 
+ if !ListP(col) {
+ err = ProcessError("fold-right needs a list as its third argument", env)
+ return
+ }
+
  list := ToArray(col)
 
  result, err = reduceFoldProc(initial, list, f, env, true)

diff --git a/tests/reduce_test.lsp b/tests/reduce_test.lsp
@@ -2,25 +2,33 @@
 
 (context "reduce"
 
- ()
-
- (it reduce-with-lambda
- (assert-eq (reduce (lambda (acc item) 0 (+ acc item)) 0 '(1 2 3))
- 6))
-
- (it reduce-with-primitive
- (assert-eq (reduce + 0 '(1 2 3))
- 6))
-
- (it reduce-building-a-list
- (assert-eq (reduce (lambda (l i) (cons i l)) '() '(1 2 3 4))
- '(4 3 2 . 1))
- (assert-eq (reduce list '() '(1 2 3 4))
- '(((1 2) 3) 4)))
-
- (it reduce-errors
- (assert-error (reduce r r '(1 2))) ;initial arg must be a function
- (assert-error (reduce + 0 1))) ;last/3rd arg must be a list
+ ()
+
+ (it reduce-with-lambda
+ (assert-eq (reduce (lambda (acc item) 0 (+ acc item)) 0 '(1 2 3))
+ 6))
+
+ (it reduce-with-primitive
+ (assert-eq (reduce + 0 '(1 2 3))
+ 6))
+
+ (it reduce-building-a-list
+ (assert-eq (reduce (lambda (l i) (cons i l)) '() '(1 2 3 4))
+ '(4 3 2 . 1))
+ (assert-eq (reduce list '() '(1 2 3 4))
+ '(((1 2) 3) 4)))
+
+ (it reduce-lengths
+ (assert-eq (reduce-left + 0 '()) 0)
+ (assert-eq (reduce-left + 0 '(1)) 1)
+ (assert-eq (reduce-left + 0 '(1 2)) 3)
+ (assert-eq (reduce-right + 0 '()) 0)
+ (assert-eq (reduce-right + 0 '(1)) 1)
+ (assert-eq (reduce-right + 0 '(1 2)) 3))
+
+ (it reduce-errors
+ (assert-error (reduce r r '(1 2))) ;initial arg must be a function
+ (assert-error (reduce + 0 1))) ;last/3rd arg must be a list
 
  (it reduce-direction
  (assert-eq (reduce-left list '() '(1 2 3 4))