Ticket #122

asteroid.vim

@@ -12,7 +12,7 @@ if exists("b:current_syntax")
 endif
 
 syn keyword basic with end do load let for function structure in is pattern 
-syn keyword basic throw this system data global return to step if not
+syn keyword basic throw this system data global return to stride if not
 syn keyword basic else or and
 
 syn keyword delimeter escape

asteroid/frontend.py

@@ -643,18 +643,18 @@ def compound(self):
         elif tt == 'TO':
             self.lexer.match('TO')
             v2 = self.exp()
-            if self.lexer.peek().type == 'STEP':
-                self.lexer.match('STEP')
+            if self.lexer.peek().type == 'STRIDE':
+                self.lexer.match('STRIDE')
                 v3 = self.exp()
                 return ('raw-to-list',
                         ('start', v),
                         ('stop', v2),
-                        ('step', v3))
+                        ('stride', v3))
             else:
                 return ('raw-to-list',
                         ('start', v),
                         ('stop', v2),
-                        ('step', ('integer', '1')))
+                        ('stride', ('integer', '1')))
 
         else:
             return v

asteroid/grammar.txt

@@ -97,7 +97,7 @@
         (
            (IS pattern) |
            (IN exp) |               /* exp has to be a list */
-           (TO exp (STEP exp)?) |   /* list comprehension */
+           (TO exp (STRIDE exp)?) |   /* list comprehension */
         )?
 
   logic_exp0

asteroid/lex.py

@@ -40,7 +40,7 @@
     'pattern'       : 'PATTERN',
     'repeat'        : 'REPEAT',
     'return'        : 'RETURN',
-    'step'          : 'STEP',
+    'stride'        : 'STRIDE',
     'structure'     : 'STRUCTURE',
     'system'        : 'SYSTEM',
     'throw'         : 'THROW',

asteroid/modules/prologue.ast

@@ -94,7 +94,7 @@ function range
   with (start:%integer,stop:%integer) do
     return [start to stop-1].
   with (start:%integer,stop:%integer,inc:%integer) do
-    return [start to stop-1 step inc].
+    return [start to stop-1 stride inc].
   with stop:%integer do
     return [0 to stop-1].
   end

asteroid/test-suites/action-tests/test073.ast

@@ -2,7 +2,7 @@
   load system math.
 
   let a = [20 to 30].
-  let array = a @[1 to a @length()-1 step 2] .
+  let array = a @[1 to a @length()-1 stride 2] .
   io @println array.
 
   assert (array == [21,23,25,27,29]).

asteroid/test-suites/regression-tests/test044.ast

@@ -1,6 +1,6 @@
 
 load system io.      
 load "util".
-let slice = [4 to 0 step -1].
+let slice = [4 to 0 stride 1].
 io @println slice.
 assert(slice is [4,3,2,1,0]).

asteroid/test-suites/regression-tests/test090.ast

@@ -3,6 +3,6 @@ load system io.
 load "util".
 
 let a = [0,1,2,3].
-let b = a@[0 to 3 step 2].
+let b = a@[0 to 3 stride 2].
 io @println b.
 assert (b is [0,2]).

asteroid/test-suites/regression-tests/test091.ast

@@ -2,7 +2,7 @@
 load system io.
 load "util".
 
-let y = [0 to 10 step 2].
+let y = [0 to 10 stride 2].
 let z = 4 in y.
 io @println z.
 assert z.

asteroid/test-suites/ug-programs/prgm-011.ast

@@ -1,10 +1,10 @@
     load system io.
 
     -- build a list of odd values
-    let a = [1 to 10 step 2].  -- list comprehension
+    let a = [1 to 10 stride 2].  -- list comprehension
     io @println ("list: " + a).
 
     -- reverse the list using a slice computed as comprehension
-    let slice = [4 to 0 step -1]. -- list comprehension
+    let slice = [4 to 0 stride 1]. -- list comprehension
     let b = a @slice.
     io @println ("reversed list: " + b).

asteroid/test-suites/ug-programs/prgm-022.ast

@@ -1,5 +1,5 @@
     load system io.
 
-    for i in 0 to 10 step 2 do
+    for i in 0 to 10 stride 2 do
         io @println i.
     end

asteroid/walk.py

@@ -1437,41 +1437,54 @@ def to_list_exp(node):
     (TOLIST,
      (START, start),
      (STOP, stop),
-     (STEP, step)) = node
+     (STRIDE, stride)) = node
 
     assert_match(TOLIST, 'to-list')
     assert_match(START, 'start')
     assert_match(STOP, 'stop')
-    assert_match(STEP, 'step')
+    assert_match(STRIDE, 'stride')
 
     (START_TYPE, start_val, *_) = walk(start)
     (STOP_TYPE, stop_val, *_) = walk(stop)
-    (STEP_TYPE, step_val, *_) = walk(step)
+    (STRIDE_TYPE, stride_val, *_) = walk(stride)
 
-    if START_TYPE != 'integer' or STOP_TYPE != 'integer' or STEP_TYPE != 'integer':
-        raise ValueError("only integer values allowed in start, stop, or step")
+    if START_TYPE != 'integer' or STOP_TYPE != 'integer' or STRIDE_TYPE != 'integer':
+        raise ValueError("only integer values allowed in start, stop, or stride")
 
     out_list_val = []
 
-    # TODO: check out the behavior with step -1 -- is this what we want?
-    # the behavior is start and stop included
-    if int(step_val) > 0: # generate the list
+    # If our stride val is > 0
+    if int(stride_val) > 0: # generate the list
+        # Get the [i]nitial inde[x] and [e]nd inde[x]
         ix = int(start_val)
-        while ix <= int(stop_val):
-            out_list_val.append(('integer', ix))
-            ix += int(step_val)
+        ex = int(stop_val)
 
-    elif int(step_val) == 0: # error
-        raise ValueError("step size of 0 not supported")
+        # Get the stride_val
+        stride_val = int(stride_val)
 
-    elif int(step_val) < 0: # generate the list
-        ix = int(start_val)
-        while ix >= int(stop_val):
-            out_list_val.append(('integer', ix))
-            ix += int(step_val)
+        # Change the direction of the stride value based on the 
+        # ends of the range. I.e. 5->1 has an implicit direction
+        # of -1, 1->5 has a direction of +1
+        direction = (1 if ix < ex else -1)
+        stride_val *= direction
+
+        # We need to modify the ending index to acccount for python
+        # ranges. For example, for 1->10 we want range(1, 10 + 1).
+        # Or, for the opposite, we want range(10, 1 - 1) to give 
+        # us the full inclusive range. Thus, we can just add our
+        # direction
+        new_ex = ex + direction
+        for i in range(ix, new_ex, stride_val):
+            out_list_val.append( ('integer', i) )
+
+    elif int(stride_val) == 0: # error
+        raise ValueError("stride size of 0 not supported")
+
+    elif int(stride_val) < 0: # generate the list
+        raise ValueError("negative stride sizes are not supported")
 
     else:
-        raise ValueError("{} not a valid step value".format(step_val))
+        raise ValueError("{} not a valid stride value".format(stride_val))
 
     return ('list', out_list_val)