Watch one program become machine work.

Follow a real program through five compiler stages, from source to result, then run your own in Venutian's own compiler.

The stepper

Follow one program through Source, Tokens, Syntax tree, Bytecode and Result. Every panel shows real output captured from the compiler at build time.

hello hello.ven

Source
The program exactly as it sits in the file, the text the compiler reads.
```
1print "Hello from Venutian"
```
Tokens
The venutian tokens command cuts that text into words, each with its kind, its value, its line and its column.
1. PRINTprintline 1 column 1
2. TEXT"Hello from Venutian"line 1 column 7
3. NEWLINEline 1 column 28
4. EOFline 3 column 1
Syntax tree
The venutian ast command shows the grammar the parser found: every statement a node, every name and literal a leaf.
- Program
  statements
  PrintStatement
  args
  TextLiteral value "Hello from Venutian"
Bytecode
The venutian disasm command lists the instructions the virtual machine runs, each operand resolved to the constant it names.

main
Offset Instruction Operand Constant
0 LOAD_CONST 0 "Hello from Venutian"
1 PRINT 1
2 HALT
Output
The venutian run command compiles the program and runs it on the native virtual machine, and this is what it printed.
```
Hello from Venutian
```
exit 0

main
Offset	Instruction	Operand	Constant
0	LOAD_CONST	0	"Hello from Venutian"
1	PRINT	1
2	HALT

grade guards.ven

Source

The program exactly as it sits in the file, the text the compiler reads.

1make grade(score)2    choose score3        is n: Integer where n >= 904            give "A"5        is n: Integer where n >= 806            give "B"7        is n: Integer where n >= 708            give "C"9        is : Integer10            give "F"11        otherwise12            give "not a number"1314print grade(95)15print grade(82)16print grade(71)17print grade(50)18print grade("ninety")

Tokens
The venutian tokens command cuts that text into words, each with its kind, its value, its line and its column.
1. MAKEmakeline 1 column 1
2. IDENTgradeline 1 column 6
3. LPAREN(line 1 column 11
4. IDENTscoreline 1 column 12
5. RPAREN)line 1 column 17
6. NEWLINEline 1 column 18
7. INDENT4line 2 column 1
8. CHOOSEchooseline 2 column 5
9. IDENTscoreline 2 column 12
10. NEWLINEline 2 column 17
11. INDENT8line 3 column 1
12. ISisline 3 column 9
13. IDENTnline 3 column 12
14. COLON:line 3 column 13
15. IDENTIntegerline 3 column 15
16. WHEREwhereline 3 column 23
17. IDENTnline 3 column 29
18. GE>=line 3 column 31
19. INTEGER90line 3 column 34
20. NEWLINEline 3 column 36
21. INDENT12line 4 column 1
22. GIVEgiveline 4 column 13
23. TEXT"A"line 4 column 18
24. NEWLINEline 4 column 21
25. DEDENT8line 5 column 1
26. ISisline 5 column 9
27. IDENTnline 5 column 12
28. COLON:line 5 column 13
29. IDENTIntegerline 5 column 15
30. WHEREwhereline 5 column 23
31. IDENTnline 5 column 29
32. GE>=line 5 column 31
33. INTEGER80line 5 column 34
34. NEWLINEline 5 column 36
35. INDENT12line 6 column 1
36. GIVEgiveline 6 column 13
37. TEXT"B"line 6 column 18
38. NEWLINEline 6 column 21
39. DEDENT8line 7 column 1
40. ISisline 7 column 9
41. IDENTnline 7 column 12
42. COLON:line 7 column 13
43. IDENTIntegerline 7 column 15
44. WHEREwhereline 7 column 23
45. IDENTnline 7 column 29
46. GE>=line 7 column 31
47. INTEGER70line 7 column 34
48. NEWLINEline 7 column 36
49. INDENT12line 8 column 1
50. GIVEgiveline 8 column 13
51. TEXT"C"line 8 column 18
52. NEWLINEline 8 column 21
53. DEDENT8line 9 column 1
54. ISisline 9 column 9
55. COLON:line 9 column 12
56. IDENTIntegerline 9 column 14
57. NEWLINEline 9 column 21
58. INDENT12line 10 column 1
59. GIVEgiveline 10 column 13
60. TEXT"F"line 10 column 18
61. NEWLINEline 10 column 21
62. DEDENT8line 11 column 1
63. OTHERWISEotherwiseline 11 column 9
64. NEWLINEline 11 column 18
65. INDENT12line 12 column 1
66. GIVEgiveline 12 column 13
67. TEXT"not a number"line 12 column 18
68. NEWLINEline 12 column 32
69. DEDENT0line 14 column 1
70. DEDENT0line 14 column 1
71. DEDENT0line 14 column 1
72. PRINTprintline 14 column 1
73. IDENTgradeline 14 column 7
74. LPAREN(line 14 column 12
75. INTEGER95line 14 column 13
76. RPAREN)line 14 column 15
77. NEWLINEline 14 column 16
78. PRINTprintline 15 column 1
79. IDENTgradeline 15 column 7
80. LPAREN(line 15 column 12
81. INTEGER82line 15 column 13
82. RPAREN)line 15 column 15
83. NEWLINEline 15 column 16
84. PRINTprintline 16 column 1
85. IDENTgradeline 16 column 7
86. LPAREN(line 16 column 12
87. INTEGER71line 16 column 13
88. RPAREN)line 16 column 15
89. NEWLINEline 16 column 16
90. PRINTprintline 17 column 1
91. IDENTgradeline 17 column 7
92. LPAREN(line 17 column 12
93. INTEGER50line 17 column 13
94. RPAREN)line 17 column 15
95. NEWLINEline 17 column 16
96. PRINTprintline 18 column 1
97. IDENTgradeline 18 column 7
98. LPAREN(line 18 column 12
99. TEXT"ninety"line 18 column 13
100. RPAREN)line 18 column 21
101. NEWLINEline 18 column 22
102. EOFline 20 column 1
Syntax tree
The venutian ast command shows the grammar the parser found: every statement a node, every name and literal a leaf.
- Program
  statements
  FunctionDecl name grade
  params
  Param name score
  body
  ChooseStatement
  subject
  Name identifier score
  branches
  ChooseBranch
  pattern
  TypePattern var_name n type_name Integer
  body
  GiveStatement
  value
  TextLiteral value "A"
  guard
  BinaryOp op >=
  left
  Name identifier n
  right
  IntegerLiteral value 90
  ChooseBranch
  pattern
  TypePattern var_name n type_name Integer
  body
  GiveStatement
  value
  TextLiteral value "B"
  guard
  BinaryOp op >=
  left
  Name identifier n
  right
  IntegerLiteral value 80
  ChooseBranch
  pattern
  TypePattern var_name n type_name Integer
  body
  GiveStatement
  value
  TextLiteral value "C"
  guard
  BinaryOp op >=
  left
  Name identifier n
  right
  IntegerLiteral value 70
  ChooseBranch
  pattern
  TypePattern type_name Integer
  body
  GiveStatement
  value
  TextLiteral value "F"
  ChooseBranch
  body
  GiveStatement
  value
  TextLiteral value "not a number"
  PrintStatement
  args
  Call
  callee
  Name identifier grade
  args
  Node 0 false
  1
  IntegerLiteral value 95
  PrintStatement
  args
  Call
  callee
  Name identifier grade
  args
  Node 0 false
  1
  IntegerLiteral value 82
  PrintStatement
  args
  Call
  callee
  Name identifier grade
  args
  Node 0 false
  1
  IntegerLiteral value 71
  PrintStatement
  args
  Call
  callee
  Name identifier grade
  args
  Node 0 false
  1
  IntegerLiteral value 50
  PrintStatement
  args
  Call
  callee
  Name identifier grade
  args
  Node 0 false
  1
  TextLiteral value "ninety"

Bytecode

The venutian disasm command lists the instructions the virtual machine runs, each operand resolved to the constant it names.

main
Offset	Instruction	Operand	Constant
0	LOAD_CONST	13	95
1	CALL	1 14	"grade"
2	PRINT	1
3	LOAD_CONST	15	82
4	CALL	1 14	"grade"
5	PRINT	1
6	LOAD_CONST	16	71
7	CALL	1 14	"grade"
8	PRINT	1
9	LOAD_CONST	17	50
10	CALL	1 14	"grade"
11	PRINT	1
12	LOAD_CONST	18	"ninety"
13	CALL	1 14	"grade"
14	PRINT	1
15	HALT

function grade(score)
Offset	Instruction	Operand	Constant
0	LOAD_NAME	1	"score"
1	STORE_NAME	0	"$choose_subject_1"
2	LOAD_NAME	0	"$choose_subject_1"
3	LOAD_CONST	2	"Integer"
4	CALL	2 3	"is_instance_of"
5	JUMP_IF_FALSE	17
6	LOAD_NAME	0	"$choose_subject_1"
7	STORE_NAME	4	"n"
8	LOAD_NAME	4	"n"
9	LOAD_CONST	5	90
10	GE
11	JUMP_IF_FALSE	16
12	LOAD_CONST	6	"A"
13	RETURN
14	UNBIND_NAME	4	"n"
15	JUMP	56
16	UNBIND_NAME	4	"n"
17	LOAD_NAME	0	"$choose_subject_1"
18	LOAD_CONST	2	"Integer"
19	CALL	2 3	"is_instance_of"
20	JUMP_IF_FALSE	32
21	LOAD_NAME	0	"$choose_subject_1"
22	STORE_NAME	4	"n"
23	LOAD_NAME	4	"n"
24	LOAD_CONST	7	80
25	GE
26	JUMP_IF_FALSE	31
27	LOAD_CONST	8	"B"
28	RETURN
29	UNBIND_NAME	4	"n"
30	JUMP	56
31	UNBIND_NAME	4	"n"
32	LOAD_NAME	0	"$choose_subject_1"
33	LOAD_CONST	2	"Integer"
34	CALL	2 3	"is_instance_of"
35	JUMP_IF_FALSE	47
36	LOAD_NAME	0	"$choose_subject_1"
37	STORE_NAME	4	"n"
38	LOAD_NAME	4	"n"
39	LOAD_CONST	9	70
40	GE
41	JUMP_IF_FALSE	46
42	LOAD_CONST	10	"C"
43	RETURN
44	UNBIND_NAME	4	"n"
45	JUMP	56
46	UNBIND_NAME	4	"n"
47	LOAD_NAME	0	"$choose_subject_1"
48	LOAD_CONST	2	"Integer"
49	CALL	2 3	"is_instance_of"
50	JUMP_IF_FALSE	54
51	LOAD_CONST	11	"F"
52	RETURN
53	JUMP	56
54	LOAD_CONST	12	"not a number"
55	RETURN
56	RETURN_NOTHING

Output
The venutian run command compiles the program and runs it on the native virtual machine, and this is what it printed.
```
A
B
C
F
not a number
```
exit 0

concurrency concurrency.ven

Source

The program exactly as it sits in the file, the text the compiler reads.

1:: 'spawn call_expr' starts a real OS thread running the call right now2:: and returns a Task immediately, without waiting. 'await task' blocks3:: until it finishes, returning its result, or re-raising its fault.45make add(a, b)6    give a + b78t = spawn add(2, 3)9print kind(t)10print await t1112:: several tasks make genuine concurrent progress13make slow_double(n)14    sleep(0.05)15    give n * 21617t1 = spawn slow_double(1)18t2 = spawn slow_double(2)19t3 = spawn slow_double(3)20print await t121print await t222print await t32324:: a fault inside a spawned task surfaces at 'await', not silently25make risky()26    give 1 / 02728failing_task = spawn risky()29attempt30    await failing_task31rescue e32    print "rescued:", e3334:: 'share'/'protect': real mutual exclusion across real threads35share counter = 03637make increment_many(count)38    i = 039    repeat while i < count40        protect counter41            counter = counter + 142        i = i + 14344tasks = []45repeat 8 times46    tasks = appended(tasks, spawn increment_many(500))4748repeat for t in tasks49    await t5051:: exactly 4000 (8 * 500) every time. 'protect' prevents lost updates52print counter

Tokens
The venutian tokens command cuts that text into words, each with its kind, its value, its line and its column.
1. MAKEmakeline 5 column 1
2. IDENTaddline 5 column 6
3. LPAREN(line 5 column 9
4. IDENTaline 5 column 10
5. COMMA,line 5 column 11
6. IDENTbline 5 column 13
7. RPAREN)line 5 column 14
8. NEWLINEline 5 column 15
9. INDENT4line 6 column 1
10. GIVEgiveline 6 column 5
11. IDENTaline 6 column 10
12. PLUS+line 6 column 12
13. IDENTbline 6 column 14
14. NEWLINEline 6 column 15
15. DEDENT0line 8 column 1
16. IDENTtline 8 column 1
17. EQ=line 8 column 3
18. SPAWNspawnline 8 column 5
19. IDENTaddline 8 column 11
20. LPAREN(line 8 column 14
21. INTEGER2line 8 column 15
22. COMMA,line 8 column 16
23. INTEGER3line 8 column 18
24. RPAREN)line 8 column 19
25. NEWLINEline 8 column 20
26. PRINTprintline 9 column 1
27. IDENTkindline 9 column 7
28. LPAREN(line 9 column 11
29. IDENTtline 9 column 12
30. RPAREN)line 9 column 13
31. NEWLINEline 9 column 14
32. PRINTprintline 10 column 1
33. AWAITawaitline 10 column 7
34. IDENTtline 10 column 13
35. NEWLINEline 10 column 14
36. MAKEmakeline 13 column 1
37. IDENTslow_doubleline 13 column 6
38. LPAREN(line 13 column 17
39. IDENTnline 13 column 18
40. RPAREN)line 13 column 19
41. NEWLINEline 13 column 20
42. INDENT4line 14 column 1
43. IDENTsleepline 14 column 5
44. LPAREN(line 14 column 10
45. NUMBER0.05line 14 column 11
46. RPAREN)line 14 column 15
47. NEWLINEline 14 column 16
48. GIVEgiveline 15 column 5
49. IDENTnline 15 column 10
50. STAR*line 15 column 12
51. INTEGER2line 15 column 14
52. NEWLINEline 15 column 15
53. DEDENT0line 17 column 1
54. IDENTt1line 17 column 1
55. EQ=line 17 column 4
56. SPAWNspawnline 17 column 6
57. IDENTslow_doubleline 17 column 12
58. LPAREN(line 17 column 23
59. INTEGER1line 17 column 24
60. RPAREN)line 17 column 25
61. NEWLINEline 17 column 26
62. IDENTt2line 18 column 1
63. EQ=line 18 column 4
64. SPAWNspawnline 18 column 6
65. IDENTslow_doubleline 18 column 12
66. LPAREN(line 18 column 23
67. INTEGER2line 18 column 24
68. RPAREN)line 18 column 25
69. NEWLINEline 18 column 26
70. IDENTt3line 19 column 1
71. EQ=line 19 column 4
72. SPAWNspawnline 19 column 6
73. IDENTslow_doubleline 19 column 12
74. LPAREN(line 19 column 23
75. INTEGER3line 19 column 24
76. RPAREN)line 19 column 25
77. NEWLINEline 19 column 26
78. PRINTprintline 20 column 1
79. AWAITawaitline 20 column 7
80. IDENTt1line 20 column 13
81. NEWLINEline 20 column 15
82. PRINTprintline 21 column 1
83. AWAITawaitline 21 column 7
84. IDENTt2line 21 column 13
85. NEWLINEline 21 column 15
86. PRINTprintline 22 column 1
87. AWAITawaitline 22 column 7
88. IDENTt3line 22 column 13
89. NEWLINEline 22 column 15
90. MAKEmakeline 25 column 1
91. IDENTriskyline 25 column 6
92. LPAREN(line 25 column 11
93. RPAREN)line 25 column 12
94. NEWLINEline 25 column 13
95. INDENT4line 26 column 1
96. GIVEgiveline 26 column 5
97. INTEGER1line 26 column 10
98. SLASH/line 26 column 12
99. INTEGER0line 26 column 14
100. NEWLINEline 26 column 15
101. DEDENT0line 28 column 1
102. IDENTfailing_taskline 28 column 1
103. EQ=line 28 column 14
104. SPAWNspawnline 28 column 16
105. IDENTriskyline 28 column 22
106. LPAREN(line 28 column 27
107. RPAREN)line 28 column 28
108. NEWLINEline 28 column 29
109. ATTEMPTattemptline 29 column 1
110. NEWLINEline 29 column 8
111. INDENT4line 30 column 1
112. AWAITawaitline 30 column 5
113. IDENTfailing_taskline 30 column 11
114. NEWLINEline 30 column 23
115. DEDENT0line 31 column 1
116. RESCUErescueline 31 column 1
117. IDENTeline 31 column 8
118. NEWLINEline 31 column 9
119. INDENT4line 32 column 1
120. PRINTprintline 32 column 5
121. TEXT"rescued:"line 32 column 11
122. COMMA,line 32 column 21
123. IDENTeline 32 column 23
124. NEWLINEline 32 column 24
125. DEDENT0line 35 column 1
126. SHAREshareline 35 column 1
127. IDENTcounterline 35 column 7
128. EQ=line 35 column 15
129. INTEGER0line 35 column 17
130. NEWLINEline 35 column 18
131. MAKEmakeline 37 column 1
132. IDENTincrement_manyline 37 column 6
133. LPAREN(line 37 column 20
134. IDENTcountline 37 column 21
135. RPAREN)line 37 column 26
136. NEWLINEline 37 column 27
137. INDENT4line 38 column 1
138. IDENTiline 38 column 5
139. EQ=line 38 column 7
140. INTEGER0line 38 column 9
141. NEWLINEline 38 column 10
142. REPEATrepeatline 39 column 5
143. WHILEwhileline 39 column 12
144. IDENTiline 39 column 18
145. LT<line 39 column 20
146. IDENTcountline 39 column 22
147. NEWLINEline 39 column 27
148. INDENT8line 40 column 1
149. PROTECTprotectline 40 column 9
150. IDENTcounterline 40 column 17
151. NEWLINEline 40 column 24
152. INDENT12line 41 column 1
153. IDENTcounterline 41 column 13
154. EQ=line 41 column 21
155. IDENTcounterline 41 column 23
156. PLUS+line 41 column 31
157. INTEGER1line 41 column 33
158. NEWLINEline 41 column 34
159. DEDENT8line 42 column 1
160. IDENTiline 42 column 9
161. EQ=line 42 column 11
162. IDENTiline 42 column 13
163. PLUS+line 42 column 15
164. INTEGER1line 42 column 17
165. NEWLINEline 42 column 18
166. DEDENT0line 44 column 1
167. DEDENT0line 44 column 1
168. IDENTtasksline 44 column 1
169. EQ=line 44 column 7
170. LBRACKET[line 44 column 9
171. RBRACKET]line 44 column 10
172. NEWLINEline 44 column 11
173. REPEATrepeatline 45 column 1
174. INTEGER8line 45 column 8
175. TIMEStimesline 45 column 10
176. NEWLINEline 45 column 15
177. INDENT4line 46 column 1
178. IDENTtasksline 46 column 5
179. EQ=line 46 column 11
180. IDENTappendedline 46 column 13
181. LPAREN(line 46 column 21
182. IDENTtasksline 46 column 22
183. COMMA,line 46 column 27
184. SPAWNspawnline 46 column 29
185. IDENTincrement_manyline 46 column 35
186. LPAREN(line 46 column 49
187. INTEGER500line 46 column 50
188. RPAREN)line 46 column 53
189. RPAREN)line 46 column 54
190. NEWLINEline 46 column 55
191. DEDENT0line 48 column 1
192. REPEATrepeatline 48 column 1
193. FORforline 48 column 8
194. IDENTtline 48 column 12
195. INinline 48 column 14
196. IDENTtasksline 48 column 17
197. NEWLINEline 48 column 22
198. INDENT4line 49 column 1
199. AWAITawaitline 49 column 5
200. IDENTtline 49 column 11
201. NEWLINEline 49 column 12
202. DEDENT0line 52 column 1
203. PRINTprintline 52 column 1
204. IDENTcounterline 52 column 7
205. NEWLINEline 52 column 14
206. EOFline 54 column 1
Syntax tree
The venutian ast command shows the grammar the parser found: every statement a node, every name and literal a leaf.
- Program
  statements
  FunctionDecl name add
  params
  Param name a
  Param name b
  body
  GiveStatement
  value
  BinaryOp op +
  left
  Name identifier a
  right
  Name identifier b
  AssignStatement
  target
  Name identifier t
  value
  SpawnExpr
  call
  Call
  callee
  Name identifier add
  args
  Node 0 false
  1
  IntegerLiteral value 2
  Node 0 false
  1
  IntegerLiteral value 3
  PrintStatement
  args
  Call
  callee
  Name identifier kind
  args
  Node 0 false
  1
  Name identifier t
  PrintStatement
  args
  AwaitExpr
  task
  Name identifier t
  FunctionDecl name slow_double
  params
  Param name n
  body
  ExprStatement
  expr
  Call
  callee
  Name identifier sleep
  args
  Node 0 false
  1
  NumberLiteral value 0.05
  GiveStatement
  value
  BinaryOp op *
  left
  Name identifier n
  right
  IntegerLiteral value 2
  AssignStatement
  target
  Name identifier t1
  value
  SpawnExpr
  call
  Call
  callee
  Name identifier slow_double
  args
  Node 0 false
  1
  IntegerLiteral value 1
  AssignStatement
  target
  Name identifier t2
  value
  SpawnExpr
  call
  Call
  callee
  Name identifier slow_double
  args
  Node 0 false
  1
  IntegerLiteral value 2
  AssignStatement
  target
  Name identifier t3
  value
  SpawnExpr
  call
  Call
  callee
  Name identifier slow_double
  args
  Node 0 false
  1
  IntegerLiteral value 3
  PrintStatement
  args
  AwaitExpr
  task
  Name identifier t1
  PrintStatement
  args
  AwaitExpr
  task
  Name identifier t2
  PrintStatement
  args
  AwaitExpr
  task
  Name identifier t3
  FunctionDecl name risky
  body
  GiveStatement
  value
  BinaryOp op /
  left
  IntegerLiteral value 1
  right
  IntegerLiteral value 0
  AssignStatement
  target
  Name identifier failing_task
  value
  SpawnExpr
  call
  Call
  callee
  Name identifier risky
  AttemptStatement
  body
  ExprStatement
  expr
  AwaitExpr
  task
  Name identifier failing_task
  rescues
  RescueClause var_name e
  body
  PrintStatement
  args
  TextLiteral value "rescued:"
  Name identifier e
  ShareStatement name counter
  value
  IntegerLiteral value 0
  FunctionDecl name increment_many effects "Concurrency"
  params
  Param name count
  body
  AssignStatement
  target
  Name identifier i
  value
  IntegerLiteral value 0
  RepeatStatement
  form
  RepeatWhile
  condition
  BinaryOp op <
  left
  Name identifier i
  right
  Name identifier count
  body
  ProtectStatement name counter
  body
  AssignStatement
  target
  Name identifier counter
  value
  BinaryOp op +
  left
  Name identifier counter
  right
  IntegerLiteral value 1
  AssignStatement
  target
  Name identifier i
  value
  BinaryOp op +
  left
  Name identifier i
  right
  IntegerLiteral value 1
  AssignStatement
  target
  Name identifier tasks
  value
  ListLiteral
  RepeatStatement
  form
  RepeatTimes
  count
  IntegerLiteral value 8
  body
  AssignStatement
  target
  Name identifier tasks
  value
  Call
  callee
  Name identifier appended
  args
  Node 0 false
  1
  Name identifier tasks
  Node 0 false
  1
  SpawnExpr
  call
  Call
  callee
  Name identifier increment_many
  args
  Node 0 false
  1
  IntegerLiteral value 500
  RepeatStatement
  form
  RepeatFor loop_var "t"
  iterable
  Name identifier tasks
  body
  ExprStatement
  expr
  AwaitExpr
  task
  Name identifier t
  PrintStatement
  args
  Name identifier counter

Bytecode

The venutian disasm command lists the instructions the virtual machine runs, each operand resolved to the constant it names.

main
Offset	Instruction	Operand	Constant
0	LOAD_NAME	13	"add"
1	BUILD_LIST	0
2	LOAD_CONST	5	2
3	LIST_APPEND
4	LOAD_CONST	14	3
5	LIST_APPEND
6	CALL	0 15	"new_map"
7	SPAWN
8	STORE_NAME	16	"t"
9	LOAD_NAME	16	"t"
10	CALL	1 17	"kind"
11	PRINT	1
12	LOAD_NAME	16	"t"
13	AWAIT
14	PRINT	1
15	LOAD_NAME	18	"slow_double"
16	BUILD_LIST	0
17	LOAD_CONST	6	1
18	LIST_APPEND
19	CALL	0 15	"new_map"
20	SPAWN
21	STORE_NAME	19	"t1"
22	LOAD_NAME	18	"slow_double"
23	BUILD_LIST	0
24	LOAD_CONST	5	2
25	LIST_APPEND
26	CALL	0 15	"new_map"
27	SPAWN
28	STORE_NAME	20	"t2"
29	LOAD_NAME	18	"slow_double"
30	BUILD_LIST	0
31	LOAD_CONST	14	3
32	LIST_APPEND
33	CALL	0 15	"new_map"
34	SPAWN
35	STORE_NAME	21	"t3"
36	LOAD_NAME	19	"t1"
37	AWAIT
38	PRINT	1
39	LOAD_NAME	20	"t2"
40	AWAIT
41	PRINT	1
42	LOAD_NAME	21	"t3"
43	AWAIT
44	PRINT	1
45	LOAD_NAME	22	"risky"
46	BUILD_LIST	0
47	CALL	0 15	"new_map"
48	SPAWN
49	STORE_NAME	23	"failing_task"
50	ENTER_ATTEMPT	24
51	LOAD_NAME	23	"failing_task"
52	AWAIT
53	POP
54	EXIT_ATTEMPT
55	JUMP	60
56	LOAD_CONST	25	"rescued:"
57	LOAD_NAME	26	"e"
58	PRINT	2
59	JUMP	60
60	LOAD_CONST	7	0
61	MAKE_SHARED
62	STORE_NAME	10	"counter"
63	BUILD_LIST	0
64	STORE_NAME	27	"tasks"
65	LOAD_CONST	30	8
66	STORE_NAME	28	"$rt_len_3"
67	LOAD_CONST	7	0
68	STORE_NAME	29	"$rt_idx_3"
69	LOAD_NAME	29	"$rt_idx_3"
70	LOAD_NAME	28	"$rt_len_3"
71	LT
72	JUMP_IF_FALSE	87
73	LOAD_NAME	27	"tasks"
74	LOAD_NAME	31	"increment_many"
75	BUILD_LIST	0
76	LOAD_CONST	32	500
77	LIST_APPEND
78	CALL	0 15	"new_map"
79	SPAWN
80	CALL	2 33	"appended"
81	STORE_NAME	27	"tasks"
82	LOAD_NAME	29	"$rt_idx_3"
83	LOAD_CONST	6	1
84	ADD
85	STORE_NAME	29	"$rt_idx_3"
86	JUMP	69
87	LOAD_NAME	27	"tasks"
88	STORE_NAME	34	"$rf_src_4"
89	LOAD_NAME	34	"$rf_src_4"
90	CALL	1 36	"$is_generator"
91	JUMP_IF_FALSE	102
92	LOAD_NAME	34	"$rf_src_4"
93	CALL	1 37	"$has_next"
94	JUMP_IF_FALSE	121
95	LOAD_NAME	34	"$rf_src_4"
96	CALL	1 38	"$next_value"
97	STORE_NAME	16	"t"
98	LOAD_NAME	16	"t"
99	AWAIT
100	POP
101	JUMP	92
102	LOAD_CONST	7	0
103	STORE_NAME	35	"$rf_idx_4"
104	LOAD_NAME	35	"$rf_idx_4"
105	LOAD_NAME	34	"$rf_src_4"
106	LEN
107	LT
108	JUMP_IF_FALSE	121
109	LOAD_NAME	34	"$rf_src_4"
110	LOAD_NAME	35	"$rf_idx_4"
111	INDEX
112	STORE_NAME	16	"t"
113	LOAD_NAME	16	"t"
114	AWAIT
115	POP
116	LOAD_NAME	35	"$rf_idx_4"
117	LOAD_CONST	6	1
118	ADD
119	STORE_NAME	35	"$rf_idx_4"
120	JUMP	104
121	LOAD_NAME	10	"counter"
122	PRINT	1
123	HALT

function add(a, b)
Offset	Instruction	Operand	Constant
0	LOAD_NAME	0	"a"
1	LOAD_NAME	1	"b"
2	ADD
3	RETURN
4	RETURN_NOTHING

function slow_double(n)
Offset	Instruction	Operand	Constant
0	LOAD_CONST	2	0.05
1	CALL	1 3	"sleep"
2	POP
3	LOAD_NAME	4	"n"
4	LOAD_CONST	5	2
5	MUL
6	RETURN
7	RETURN_NOTHING

function risky()
Offset	Instruction	Operand	Constant
0	LOAD_CONST	6	1
1	LOAD_CONST	7	0
2	DIV
3	RETURN
4	RETURN_NOTHING

function increment_many(count)
Offset	Instruction	Operand	Constant
0	LOAD_CONST	7	0
1	STORE_NAME	8	"i"
2	LOAD_NAME	8	"i"
3	LOAD_NAME	9	"count"
4	LT
5	JUMP_IF_FALSE	23
6	PROTECT_ENTER	10	"counter"
7	ENTER_ATTEMPT	11
8	LOAD_NAME	10	"counter"
9	LOAD_CONST	6	1
10	ADD
11	STORE_NAME	10	"counter"
12	EXIT_ATTEMPT
13	PROTECT_EXIT	10	"counter"
14	JUMP	18
15	PROTECT_EXIT	10	"counter"
16	LOAD_NAME	12	"$protect_exc_2"
17	RAISE
18	LOAD_NAME	8	"i"
19	LOAD_CONST	6	1
20	ADD
21	STORE_NAME	8	"i"
22	JUMP	2
23	RETURN_NOTHING

Output
The venutian run command compiles the program and runs it on the native virtual machine, and this is what it printed.
```
Task
5
2
4
6
rescued: Division by zero.
4000
```
exit 0

The playground

Nine real programs, each with its recorded output and timing. Run compiles a program with Venutian's self hosted compiler and executes it on the native virtual machine, compiled to WebAssembly and running in your browser.

hello.ven

print "Hello from Venutian"

Hello from Venutian

guards.ven

make grade(score)
    choose score
        is n: Integer where n >= 90
            give "A"
        is n: Integer where n >= 80
            give "B"
        is n: Integer where n >= 70
            give "C"
        is : Integer
            give "F"
        otherwise
            give "not a number"

print grade(95)
print grade(82)
print grade(71)
print grade(50)
print grade("ninety")

A
B
C
F
not a number

concurrency.ven

:: 'spawn call_expr' starts a real OS thread running the call right now
:: and returns a Task immediately, without waiting. 'await task' blocks
:: until it finishes, returning its result, or re-raising its fault.

make add(a, b)
    give a + b

t = spawn add(2, 3)
print kind(t)
print await t

:: several tasks make genuine concurrent progress
make slow_double(n)
    sleep(0.05)
    give n * 2

t1 = spawn slow_double(1)
t2 = spawn slow_double(2)
t3 = spawn slow_double(3)
print await t1
print await t2
print await t3

:: a fault inside a spawned task surfaces at 'await', not silently
make risky()
    give 1 / 0

failing_task = spawn risky()
attempt
    await failing_task
rescue e
    print "rescued:", e

:: 'share'/'protect': real mutual exclusion across real threads
share counter = 0

make increment_many(count)
    i = 0
    repeat while i < count
        protect counter
            counter = counter + 1
        i = i + 1

tasks = []
repeat 8 times
    tasks = appended(tasks, spawn increment_many(500))

repeat for t in tasks
    await t

:: exactly 4000 (8 * 500) every time. 'protect' prevents lost updates
print counter

Task
5
2
4
6
rescued: Division by zero.
4000

Run it on your own machine.

macOS, Apple silicon

curl -fsSL https://venutian.org/install.sh | sh

Linux

x86_64 and arm64. Ubuntu, Debian, Fedora, Alpine and friends.

curl -fsSL https://venutian.org/install.sh | sh

Windows

irm https://venutian.org/install.ps1 | iex

powershell -c "irm https://venutian.org/install.ps1 | iex"

For Macs with Apple silicon.

curl -fsSL https://venutian.org/install.sh | sh

x86_64 and arm64. Ubuntu, Debian, Fedora, Alpine and friends.

curl -fsSL https://venutian.org/install.sh | sh

irm https://venutian.org/install.ps1 | iex

powershell -c "irm https://venutian.org/install.ps1 | iex"

Self hosting in five stages

Venutian's own compiler pipeline is written in Venutian, one stage at a time, each stage checked against the reference implementation before the next one starts.

Tokenizer
A real tokenizer for a small expression language, written entirely in Venutian (examples/self_hosting_lexer.ven).
Lexer port
A line for line port of the production lexer, checked token by token against the reference lexer over the whole example corpus.
Parser and checker
Ports of the production parser and semantic analyzer, checked by AST equality and accept and reject tests.
Code generator
A port of the production code generator (1,133 lines of Venutian) plus the VBC serializer, so the whole pipeline runs in Venutian and emits a loadable .vbc file.
Native VM
A from scratch native virtual machine with no third party libraries. From here, new programs compile and run with nothing but Venutian in the loop.

Native ahead of time compilation

venutian build --native compiles ahead of time with the same compiler and binary that produced every number on the performance page. Two decisions do the work: the recursive body of a hot function is inlined once, and a frameless base case skips building a stack frame for the branch that just returns.

On fib(30) the result runs 43.6 million instructions against clang's 45.5 million on the same round: 1.000x the cycles of clang -O2 and 0.985x the wall time, from a compiler written in Venutian.

Terminal, macOS

$ venutian build --native hello.ven
n3: wrote hello bytes=33440 words=2253 functions=1

Then run it

$ ./hello
Hello from Venutian

Next chapter Tooling

Watch one program become machine work.

The stepper

Source

Tokens

Syntax tree

Bytecode

Output

Source

Tokens

Syntax tree

Bytecode

Output

Source

Tokens

Syntax tree

Bytecode

Output

The playground

macOS, Apple silicon

Linux

Windows

Self hosting in five stages

Tokenizer

Lexer port

Parser and checker

Code generator

Native VM

Native ahead of time compilation